Event-Related Desynchronization of Frontal-Midline Theta Rhythm During Preconscious Auditory Oddball Processing
Masaru Kawamata, Eiji Kirino, Reiichi Inoue and Heii Arai
ABSTRACT
The goal of this study was to explore the frontal-midline theta rhythm (Fm theta) generation mechanism employing event-related desynchronization/synchronization (ERD/ERS) analysis in relation to task-irrelevant external stimuli. A dual paradigm was employed: a videogame and the simultaneous presentation of passive auditory oddball stimuli. We analyzed the data concerning ERD/ERS using both Fast Fourier Transformation (FFT) and wavelet transform (WT).
In the FFT data, during the periods with appearance of Fm theta, apparent ERD of the theta band was observed at Fz and Cz. ERD when Fm theta was present was much more prominent than when Fm theta was absent. In the WT data, as in the FFT data, ERD was seen again, but in this case the ERD was preceded by ERS during both the periods with and without Fm theta. Furthermore, the WT analysis indicated that ERD was followed by ERS during the periods without Fm theta. However, during Fm theta, no apparent ERS following ERD was seen.
In our study, Fm theta was desynchronized by the auditory stimuli that were independent of the video game task used to evoke the Fm theta. The ERD of Fm theta might be reflecting the mechanism of “positive suppression” to process external auditory stimuli automatically and preventing attentional resources from being unnecessarily allocated to those stimuli. Another possibility is that Fm theta induced by our dual paradigm may reflect information processing modeled by multi-item working memory requirements for playing the videogame and the simultaneous auditory processing using a memory trace. ERS in the WT data without Fm theta might indicate further processing of the auditory information free from “positive suppression” control reflected by Fm theta.
Creutzfeldt-Jakob Disease Presenting as Hyperparathyroidism and Generalized Tonic Status Epilepticus
Hulya Karatas, Nese Dericioglu, Oguzhan Kursun and Serap Saygi
ABSTRACT
Creutzfeldt-Jakob disease is the most common disorder among the very rare human transmissible subacute spongiform encephalopathies. Sporadic, familial or iatrogenic forms of the disease can be seen. The common presentations of the disease include rapidly progressive cognitive decline, behavioral changes, visual disturbances and cerebellar dysfunction. Hyperparathyroidism and toxicity of lithium and bismuth have been reported to induce similar symptoms and EEG findings, leading to a Creutzfeldt-Jakob like syndrome. We report a very rare case of Creutzfeldt-Jakob disease presenting with hyperparathyroidism and generalized tonic status epilepticus.
EEG Coherence for a Patient With Marchiafava-Bignami Disease
Shih-Chin Fang, Jung-Lung Hsu and Wei-Hung Chen
ABSTRACT
We evaluated a 39-year-old chronic alcoholic man with acute multiple cognitive impairment and callosal lesion seen in MRI, diagnosed as Marchiafava-Bignami disease (MBD), using analysis of electroencephalography (EEG) coherence. Three EEG sessions were recorded in the first week, the second and eighth month after disease onset in the MBD patient. Inter-hemispheric coherence (IhC), parasagittal coherence (PsC) and spatially averaged coherence (SAC) were computed. The results were compared with normative data from 30 age-matched healthy subjects.
Mean values for IhC, PsC and SAC were significantly decreased during the acute stage of the disease (P<0.01). The IhC values remained low (P<0.01), however, PsC and SAC values rebounded in follow-up study. The IhC and SAC values were lowest in the frontal region, consistent with the main pathological involvement in the anterior two-thirds of the corpus callosum and early involvement of frontal cortex.
In conclusion, MBD may manifest as a cerebral-disconnection state, which can be quantified using EEG-coherence analysis. EEG-coherence may serve as a useful tool for MBD diagnosis and evaluation.
Continued, abstracts of presentations at the 4th Annual Joint Meeting of the EEG and Clinical Neuroscience Society (ECNS) and the International Society for NeuroImaging in Psychiatry (ISNIP), in Montreal, Quebec, Canada, September 19-23, 2007.
Current Brain Imaging of Nicotine/Tobacco Smoking Research
Chair: Domino E F, University of Michigan, Ann Arbor, Michigan, USA
Topographic electroencephalographic (EEG) recordings lack the precision of brain localization of functional magnetic resonance imaging (fMRI) and positron emission tomography (PET). Hence, there are few attempts to correlate the regional brain data obtained with each technology. We have been privileged to use EEG and PET methods to study similar groups of overnight abstinent tobacco smokers before and after smoking the first cigarette of the day or after nasal nicotine. The EEG studies generated mean absolute power maps with quadratic interpolation of delta, theta, alpha1, alpha2, beta1 and beta2 activity. The PET studies involved [15O] labeled water for normalized regional cerebral blood flow (rCBF), [18F]fluorodeoxyglucose for regional cerebral metabolism of glucose (rCMglu), [11C]raclopride for dopamine (DA), and [11C]carfentanil for endogenous mu opioid release. After smoking average nicotine cigarettes, a statistically significant mean increase in alpha2 activity occurred, predominantly in occipital scalp recordings over visual association areas 18 and 19. In the PET studies, there were significant rCBF changes in occipital brain areas after smoking an average nicotine yield cigarette, or nasal nicotine. Area 17 of the visual striate cortex showed a larger increase in rCBF relative to visual association areas 18 and 19. After nasal nicotine, there was a small reduction in global CMRglu. Normalized data indicated that visual cortex, including cuneus, occipito-temporal gyrus and thalamus, had increased rCMRglu. Tobacco smokers had increased DA release in the ventral striatum, and both increases (cingulate cortex) and decreases (amygdala, thalamus, ventral striatum) of endogenous mu opioid peptides, as measured by PET.
Nicotine and Attention: Event-Related Potential Investigations in Nonsmokers
Knott V J, University of Ottawa Institute of Mental Health Research, Ottawa, Ontario, Canada
Research into the effects of nicotine and smoking on cognition has largely confirmed the subjective reports of smoking, showing smoking abstinence to disrupt and smoking/nicotine to restore cognitive functioning. Evidence of performance improvements in nonsmokers has provided support for the absolute effects of nicotine on cognitive processes which are independent of withdrawal relief, but the mechanisms underlying its pro-cognitive properties still remain elusive. The attentional facilitation frequently reported with smoking/nicotine may be indirectly related to its arousal-enhancing actions, as evidenced electroencephalographically (EEG) by fast frequency power increments, or it may reflect nicotine’s direct modulating effects on neural processes governing stimulus encoding, selection and rejection. Event-related potential (ERP) components extracted during the performance of cognitive tasks have proven to be sensitive to early pre-attentive and later attention-dependent processes which are not otherwise reflected in behavioral probes. To date, the majority of ERP studies have been conducted with smokers using passive non-task paradigms or non-demanding “oddball” tasks. This presentation will emphasize our recent ERP investigations with acute nicotine polacrilex (6 mg) administrated to nonsmokers, and with a battery of behavioral performance paradigms focusing on intra- and inter-modal selective attention and distraction processes. ERP findings of nicotine-augmented attention evidenced with N100, MMN, P300 and RON component alterations add support to the contention that nicotine may be being used by smokers as a “pharmacological tool” for tuning cognitive functions relating to the automatic and controlled aspects of input selection and processing.
The EEG of Abstinent Cocaine Abusers: The Role of Cigarette Smoking
Herning R I, Better W, Gorelick D A, Cadet J L
National Institute on Drug Abuse, NIH, Baltimore, Maryland, USA
Chronic cocaine abuse has been associated with medical complications and EEG alterations. Most cocaine abusers (> 83%) also smoke tobacco cigarettes (U.S. Department of Health and Human Services, 2006). As a first step toward identifying possible relationships between the EEG of abstinent cocaine abusers and cigarette smoking, cocaine abusers who smoked (125), cocaine abusers who did not smoke (15), control subjects who smoked (15) and control subjects who did not smoke (29) were studied. A 3-minute, resting, eyes-closed EEG was recorded from eight electrodes (F3, C3, P3, O1, F4, C4, P4, and O2). The artifact-free EEG was converted to six frequency bands (delta, theta, alpha1, alpha2, beta1 and beta2) using a Fast Fourier Transform. All cocaine abusers were tested within five days of admission to a closed research ward; control subjects were tested at an outpatient visit. Subjects did not smoke for at least 1 hour before EEG testing. Absolute power in the delta, theta, alpha2, and beta2 bands was significantly lower for both control subjects and cocaine abusers who smoked than for their counter parts who did not smoke tobacco cigarettes (p< 0.05). Relative power in the beta1 band was significantly higher for both control subjects and cocaine abusers who smoked than for their counter parts who did not smoke tobacco cigarettes (p< 0.05). No significant differences were observed between cocaine abusers and control subjects in any absolute EEG bands. Previous studies investigating the EEG of abstinent cocaine abusers found decreases in EEG delta and theta power, but the tobacco smoking status of the subjects was not reported in these studies. These findings may help explain conflicting findings in the literature concerning the EEG of abstinent cocaine abusers.
Supported by the Intramural Research Program, NIH, National Institute on Drug Abuse.
Brain Imaging of Tobacco Smoking: Insights into Addiction
Rose J E, Duke University Medical Center, Durham, North Carolina, USA
While the tenacity of tobacco addiction is well known, it is unclear what brain mechanisms underlie this addiction. Nicotine plays a major role in reinforcing tobacco use, and recent studies have offered new insights into nicotine’s reinforcing effects. Studies will be discussed that have compared addicted smokers with nondependent “chippers”. By comparing these groups, in terms of the pharmacokinetics and functional effects of inhaled nicotine, brain correlates of dependence have been identified. Results will be discussed that link dependence not only to dopamine reward pathways, but also to brain structures such as the thalamus and habenula, which have high densities of nicotinic receptors and are involved in neuropsychological processes such as sensory gating and stress coping.
Functional Neuroimaging of Cigarette Addiction.
Dagher A, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
Exposure to stimuli previously paired with drug use can induce various conditioned responses in drug addicts, including craving and drug seeking.1 Several functional brain imaging studies have investigated the neural response to conditioned drug cues for nicotine.2,3 In these studies, drug cues elicit activation of neural circuitry thought to encode the motivational and emotional value of the drug, and play a role in the planning and control of behavior.
We have shown that the brain response to conditioned cues in cigarette smokers is modulated by contextual factors, such as drug availability and withdrawal.3 Our research and other work suggest that the prefrontal cortex has an important role in modulating the response to drug cues. Stress has been identified as a major contributor to both drug seeking and relapse in addicted individuals.4 Exposure to stress increases self-reports of craving in drug users, including cigarette smokers.5 However, little is known about the neural mechanisms by which stress perpetuates drug taking, or how stress and conditioning factors interact to augment the vulnerability to drug abuse. We will present results from fMRI studies that aim to understand these phenomena.
REFERENCES
1. Tiffany ST. Psychol Rev 1990; 97:147.
2. Brody AL, et al. Arch Gen Psychiatry 2002; 59: 1162.
3. McBride D, Barrett SP, Kelly JT, Aw A, Dagher A. Neuropsychopharmacology 2006; Apr 5.
4. Sinha R. Psychopharmacology (Berl) 2001; 158: 343.
5. Perkins KA, Grobe JE. Br J Addict 1992; 87:1037.
fMRI Imaging of the Effects of Smoked Tobacco and Placebo Tobacco
Lindsey K P, Frederick B deB, Ryan ET, Nickerson L D, Lukas S E
Brain Imaging Center, McLean Hospital, Belmont, Massachusetts, USA
Tobacco is the most frequently abused drug worldwide. Despite the high prevalence of abuse, little is known about the acute effects of smoking on brain. To address this question, experiments were performed in human smokers using functional magnetic resonance imaging (fMRI) during tobacco cigarette and placebo tobacco smoking. A nonmetallic smoking device was constructed and evaluated for its ability to deliver smoke and nicotine to subjects using a paced smoking paradigm. Subjects smoked either a Marlboro Red brand tobacco cigarette or a Quest “Nicotine Free” cigarette (containing only 0.03 mg nicotine) during fMRI scanning with concurrent assessment of heart rate and changes in subjective mood state. Visual analog scales for mood states were presented every 2.5 minutes throughout the functional scan. Using General Linear Modeling techniques, changes in subjective sensation of “high” after smoking tobacco were found to be most highly correlated with BOLD signal change in the bilateral anterior nucleus of the thalamus, bilateral caudate head and tail, bilateral posterior cingulate (these and all subsequent correlations were found to be significant at p£0.0001). These findings are consistent with both the reinforcing properties of nicotine and the anatomical distribution of terminals emanating from regions of high nicotinic acetylcholine receptor density. Changes in subjective sensation of “high” after smoking placebo tobacco were most highly correlated with BOLD signal change in the orbitofrontal cortex, and dorsolateral prefrontal cortex. These findings are consistent with the cognitive components of reward mediated by conditioned reinforcers only in the absence of active drug. This study is the first to assess and compare changes in BOLD signal and its relationship to reported subjective effects during active tobacco and placebo smoking.
This work is supported by NIDA Grants K01 021231 (KPL), R01 DA 03994 (SEL), and K05 00343 (SEL).
Wake and REM Sleep EEG Coherence in Adults With High Functioning Autism
Léveillé C, Bolduc C, Limoges E, Braun C M J, Mottron L, Godbout R
Hôp. Rivière-des-Prairies, Université de Montréal, Université du Québec à Montréal, Canada
Introduction: Anatomical, brain imaging and behavioral studies suggest the existence of atypical functional maps in autistic spectrum disorders (ASD). The aim of the present study was to analyze intra- and interhemispheric transfer in ASD at rest and during REM sleep by using EEG coherence.
Method: Six adults with ASD and normal intelligence (21.8 ±3.9 years) and six typically developed individuals (22.7 ± 3.5 years) were recorded in a sleep laboratory for two consecutive nights, using a full EEG montage. Spectral analysis was performed on 60 seconds of artifact-free EEG recorded during waking (with eyes closed) and REM sleep. Coherence analysis was performed on total spectrum (0.75-20.25 Hz) for intra- and interhemispheric pairs of recording sites. Results were compared with Mann-Whitney U-tests.
Results: During waking, ASD group showed less intra-hemispheric coherence than controls between anterior recording sites (F3-C3: p =.04; F4-C4: p=.04) while more coherence was found between posterior recording sites (P3-O1: p =.003; P4-O2: p=.01). There were no interhemispheric differences during waking. During REM sleep, the ASD group showed more inter-hemispheric coherence than controls at the temporal and temporo-parietal sites (T7-T8: p=.04; TP7-TP8: p=.02).
Conclusion: These results support the notion of an atypical pattern of inter-regional transfer of information in autism. The fact that waking and REM sleep yielded dissimilar differences may point toward state-specific connectivity disorders at the cortico-cortical and callosal levels.
Corresponding author: Cathy Léveillé:
Effects of Selective SWS and REM Sleep Loss on Automatic Attention: an Event-Related EEG Study
Zerouali Y, Hossein A, Jemel B, Godbout R
Hôp. Rivière-des-Prairies, Université de Montréal, Canada
Introduction:The link between total sleep deprivation and attention decrement is well known but the respective contribution of slow wave sleep (SWS) and REM sleep is not. The aim of this study was to characterize the effects of SWS vs. REM sleep loss on automatic attention.
Method: Ten young adults (5M, 5W; 22.3 years old) were tested. Since SWS is mainly found in the first half of the night and REM sleep in the second half, participants were submitted to three sleep conditions: a full night (FN), a first-half sleep deprivation night (1H) and a second-half sleep deprivation night (2H). The following morning, the EEG of participants was recorded with a simple auditory oddball task, testing for automatic attention (AA). Using 58 electrodes, we computed the “Mismatch negativity” (MMN) wave in the event-related potential (ERP) brain activity to evaluate the AA.
Results: MMN amplitude was significantly reduced and latency increased following the 2H night compared to FN and 1H. Statistical effects were more prevalent over the frontal and temporal recording areas.
Conclusion: The restoration of automatic attention is mainly processed during REM sleep, which confirms results from previous studies in rat models. The anterior cortex seems to be more sentitive to sleep loss.
Corresponding author: Younes Zerouali:
Spectral Analysis of Non-REM Sleep EEG in Boys With Attention-Deficit/Hyperactivity Disorder
Gingras MA, Labrosse M, Chevrier E, Lageix P, Guay M C, Braun C M J, Godbout R
Hôp. Rivière-des-Prairies, Université de Montréal, Université du Québec à Montréal, Canada
Introduction: EEG studies performed in children with Attention-Deficit/Hyperactivity Disorder (ADHD) during waking unsystematically point toward abnormalities in frontal, temporal, parietal as well as occipital regions. Quantified analysis of REM sleep EEG shows less slow-wave activity (SWA: 0.75-2.25 Hz) than controls selectively at frontal recording sites. In the present study, we analyzed non-REM sleep EEG in boys with ADHD (Gingras et al., ESRS 2006).
Method: Six boys diagnosed with ADHD (age: 10.3 ± 1.2) were recorded for two consecutives nights using a full EEG montage (Fp1, Fp2, F7, F8, C3, C4, T3, T4, P3, P4, O1 and O2). Comorbidity was an exclusion criterion. Methylphenidate was withdrawn for at least 48 hours in the three boys that were previously exposed to treatment. The ADHD group was compared to six healthy boys (age: 10.5 ± 1.8). Spectral analysis of night 2 EEG was performed on non-REM sleep (stages 2, 3 and 4). Comparisons between groups were made for each electrode using t-tests.
Results: Compared to controls, ADHD boys generated less SWA in frontal (F7, p<.025) and parietal (P3, p<.027) regions.
Conclusion: SWA during non-REM sleep is thought to reflect homeostatic sleep propensity. The fact that frontal and parietal SWA was found to be decreased during both non-REM and REM sleep indicates that a more general impairment of the thalamo-cortical loop prevails in ADHD boys.
Corresponding author: Marc-André Gingras:
Spectral Analysis of REM Sleep EEG in Boys With Attention-Deficit/Hyperactivity Disorder
Gingras M A, Labrosse M, Chevrier E, Lageix P, Guay M C, Braun C M J, Godbout R
Hôp. Rivière-des-Prairies, Université de Montréal, Université du Québec à Montréal, Canada
Introduction: EEG studies performed in children with Attention-Deficit/Hyperactivity Disorder (ADHD) during waking unsystematically point toward abnormalities in frontal, temporal, parietal as well as occipital regions. In order to control for some of the methodological shortcomings of previous studies, we recorded the EEG of ADHD boys during REM sleep, a state of endogenous activation of the thalamo-cortical loop.
Method: Six boys diagnosed with ADHD (age: 10.3 ± 1.2) were recorded for two consecutives nights using a full EEG montage (Fp1, Fp2, F7, F8, C3, C4, T3, T4, P3, P4, O1 and O2). Comorbidity was an exclusion criterion. Methylphenidate was withdrawn for at least 48 hours in the three boys that were previously exposed to treatment. The ADHD group was compared to six healthy boys (age: 10.5 ± 1.8). Spectral analysis of night 2 EEG activity was performed on the first three REM periods. Quantified EEG analysis was performed on 45 four-second artifacts free epochs of REM sleep, equally distributed over the first three REM periods. Results were compared with a Group x EEG band ANOVA for each electrode followed by LSD post hoc tests.
Results: The main finding was that ADHD boys generated less slow activity (0.75-2.25 Hz) than controls, occurring selectively at frontal recording sites: Fp1 (p<.02), F7 (p<.006) and F8 (p<.06).
Conclusion: These results suggest the existence of an impairment of the thalamo-frontocortical loop in ADHD.
Corresponding author: Marc-André Gingras:
NonREM Sleep EEG and Attention Performance in Drug-Naive Persons With Schizophrenia and Controls
Dubuc M J, Forest G, Poulin J, Stip E, Godbout R, Hôp. Rivière-des-Prairies; Hôp. Louis-H. Lafontaine;
Université de Montréal; Université du Québec en Outaouais, Canada
Introduction: It is known that daytime cognitive performance can be correlated with measures of nonREM sleep. Here we report on a relationship between selective attention and non-REM sleep EEG activity in healthy persons and drug-naive persons with schizophrenia.
Method: Six acute patients never exposed to neuroleptics (1 woman, 5 men, 33.8 ± 19.1 years old) and six healthy controls (2 women, 4 men, 21.0 ± 5.5 years old) were recorded for two consecutive nights with a 10-electrodes EEG montage. Absolute spectral power of nonREM sleep EEG of night two was computed for the first 7 hours of sleep. A selective attention task was administered in the morning following night 2. Mann-Whitney U-tests were used to compare groups on median reaction times and EEG. The correlation between attention and EEG activity was estimated separately for each group using Spearman’s rho.
Results: Participants with schizophrenia displayed less delta activity (0.75-3.75 Hz) than controls on frontal and temporal electrodes. They were also significantly slower than controls on the selective attention task (p < .05). Control participants showed a significant positive correlation between performance and beta (13.00 -30.00 Hz) activity during stages 3-4 sleep for frontal and temporal electrodes. No significant correlation was found in patients with schizophrenia.
Conclusion: The present results suggest nonREM sleep EEG correlates with attention in healthy persons but and this relationship may not be present in persons with schizophrenia.
Corresponding author: Marie-Josée Dubuc:
Evening vs. Morning Wake EEG Activity in Adolescents With Anxiety Disorders
Gauthier A K, Chevrette T, Chevrier E, Bouvier H, Godbout R
Hôpital Rivière-des-Prairies; Hôpital Louis-H. Lafontaine; Université de Montréal, (Québec) Canada
Introduction: We have demonstrated previously that adolescents diagnosed with an anxiety disorder show sleep disorders when recorded polysomnographically (APSS 2005, 2006). In the present study, we report wake EEG activity before and after sleep in these anxious adolescents.
Method: Thirteen adolescents with an anxiety disorder (8 males, 14.16 ±1.5 years) and 15 controls (8 males, 15 ±1.25 years) were recorded for two nights. On the second night, EEG recording with eyes closed were obtained in the evening and in the morning for 5 minutes each. Spectral analysis was performed on 12 four-seconds artifact-free epochs. The following frequency bands were generated for C3, C4, O1 and O2 electrodes: delta 1 (0.75-2.25 Hz), delta 2 (2.5-3.75 Hz), delta total (0.75-3.75 Hz), theta (4-7.75 Hz), alpha 1 (8-10 Hz), alpha 2 (10.25-12.75 Hz), alpha total (8-12.75 Hz), sigma (11.75-14.75 Hz), beta 1 (13-19.75 Hz), beta 2 (20-30 Hz) and beta total (13-30 Hz). Results were compared using ANOVAs and Tukey post-hoc tests.
Results: Evening EEG activity did not differ between both groups. In the morning, however, the patients showed higher activity than controls at C3 and C4 (0.75-10Hz and 13-20Hz) and at O1 and O2 (2.5-7.75 Hz).
Conclusion: These results suggest that restorative functions of sleep may not be optimally operational in adolescents with anxiety disorders. We are now investigating whether these topographic and frequency-specific differences with controls are associated with daytime measures of clinical state and neuropsychological functioning.
Corresponding author: Anne-Karine Gauthier:
EEG Findings in Aggressive, Violent and Psychopathic Subjects
Peters D. C. II, Boutros N. N., Wayne State University School of Medicine, Detroit, Michigan
Introduction: Aggressive and violent behavior is a public health crisis. Electroencephalography (EEG) techniques have provided several promising paradigms for investigating this crisis, assessing neurological function, and correlating behavior and brain activation patterns. However, despite early promising attempts in Clinical EEG, and recent Quantitative EEG (QEEG) and Event Related Potential (ERP) investigations, the electrophysiological correlates of aggressive and violent behavior remain less than clearly defined.
Methods: We employed Medline, Psychoindex and citation reviews to assess previous attempts at delineating EEG findings in violent, aggressive and psychopathic subjects. Clinical EEG findings were reviewed back to the 1940s with more recent QEEG and ERP findings.
Results: Despite a lack of consistent, clear, and specific findings, patterns do emerge. Clinical "EEG abnormalities" are widely reported in approximately 50% of violent and aggressive subjects. Clinical EEG studies reporting the type of abnormality detected in EEG tracings often reported epileptiform spikes or "abnormal discharges" especially in explosively violent subjects, leading to the theory of aggression as an expression of epilepsy. Early clinical EEG findings of increased delta wave and decreased theta wave activity in aggressive subjects have been largely confirmed by more recent QEEG findings which have localized the dysfunctional delta wave activity to the left temporal, frontal, and parietal lobes and have provided good evidence of increased lateralization in this population. ERP investigations in psychopathology have also provided evidence for the involvement of these regions and have suggested a dysfunctional limbic circuit.
Discussion: Implications and directions for future research are discussed.
16th Annual Conference of the Australasian Society for Psychophysiology
December 9-11, 2006
John Curtin School for Medical Research, The Australian National University, Canberra, Australia
ABSTRACTS OF PRESENTED PAPERS
These are listed by alphabetical order of the first authors surname.
The MMN Memory Trace Effect: Differential Contributions of Repetition Positivity and Deviant Negativity
Thamasin Amos, Rowena Cooper and Pat Michie
Newcastle University, Newcastle, Australia
Abstract: The Mismatch Negativity (MMN) memory trace effect has been attributed to changes in the responsiveness to deviant stimuli that occur with differing deviant probability (Naatanen, 1992). Recently, it has been suggested that an adaptation of the standard stimulus response, Repetition Positivity (RP), may account for this effect (Baldeweg, Klugman, Gruzelier, & Hirsch, 2004). In this study, an auditory, roving standard paradigm was used to investigate the effect of stimulus repetition on standard and deviant ERPs to frequency and duration deviants. RP phenomenon, occurring in standard ERPs, accounted for the MMN memory trace effect rather than the negativity in the deviant ERP. Excessive noise in the deviant ERPs may explain this null finding. Regardless, it is clear that there are two distinct processes that contribute to the MMN memory trace effect. Email: Thamasin Amos:
Caffeine Effects on ERPs and Performance in an Auditory Go/NoGo Task
Robert J. Barry, Adam R. Clarke, Stuart J. Johnstone and Jacqueline A. Rushby
Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: Our previous work showed that caffeine produces increased skin conductance level, a global reduction in EEG power in the alpha band, and a global increase in alpha frequency, all markers of arousal increase. This suggests that caffeine can be used to manipulate arousal level without the confounds associated with task-related activation. This study examined such caffeine effects on ERPs and performance. We examined the effects of a single oral dose of caffeine (250 mg) in a randomised double-blind placebo-controlled repeated-measures cross-over study. Subjects were asked to abstain from caffeine for 4 hours before testing sessions (one week apart). A simple auditory Go/NoGo task was used, with a random mix of 75 tones at 1000 Hz and 75 at 1500 Hz. All tones were 60 dB, 50 ms duration (rise/fall time 5 ms), with SOA 1100 ms. The “Go” tone differed between sessions within subject. The major effect of caffeine was an increase in P3b amplitudes to Go stimuli, with no change in P3b latency. There was a reduction in RT, but no effects on RT variability, omission or commission errors. The results suggest that caffeine differentially improves later response-execution (rather than sensory) aspects of task performance. Email: Robert J. Barry:
Arousal-State Modulation in AD/HD: An Event-Related Potential Investigation of Inhibition
Nicholas Benikos and Stuart J. Johnstone
University of Wollongong, Wollongong, Australia
Abstract: Using behavioural and ERP measures, this study investigated the effect of arousal-state modulation, via manipulation of stimulus event-rate, on response inhibition in children with Attention-Deficit/Hyperactivity Disorder (AD/HD). Seventeen children with AD/HD, aged 7 to 14 years, and 17 age-, sex-, and IQ- matched controls performed a cued visual Go/No-Go (70% Go probability) task using three event-rates (fast, medium, slow). Task performance, skin conductance level and the ERP indices to Warning, Go and No-Go stimuli were examined for group differences. While the groups did not differ in No-Go commission errors across conditions, the AD/HD group showed increased N2 latency and No-Go commission errors during the fast event-rate. Further, the children with AD/HD displayed larger N2 and P3 amplitude to Warning stimuli in the medium and fast conditions respectively. Although deficient response inhibition has been proposed as the core deficit in AD/HD, the results of the present study highlight the key role of arousal-state factors. Group differences found in the processing of Warning ERPs indicate that this effect extends to the processing of task irrelevant stimuli. Email: Nicholas Benikos:
P300 Changes as a Function of Target and Nontarget Intervals
Michelle Brennan, Craig J. Gonsalvez and Robert J. Barry
Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: The P300 has been shown to be affected by target stimulus probability, stimulus sequence structure and interstimulus interval (ISI). More recently, a series of studies has demonstrated that the target-to-target interval (TTI), and not probability or ISI, is the critical determinant of P300 amplitude, and is responsible for P300 changes observed in oddball and single-stimulus tasks previously attributed to probability, sequential structure and ISI. TTI increases reliably and linearly augment P300 amplitude and decrease P300 latency. However, it is as yet unclear whether increases of P300 amplitude observed to target intervals will also extend to nontargets and nontarget intervals. In other words, would increases of non-target intervals also increase P300s to equiprobable nontargets in a linear fashion? The current study addressed this question by having thirty undergraduate students perform a three-stimulus visual oddball task where infrequent targets (p=.25) and infrequent nontargets (p=.25) were embedded among frequent nontargets or standards (p=.50). Both targets and infrequents were presented at 7 different intervals ranging from 1.5 to 10.5 seconds. Results confirmed the TTI effect on target P300 amplitude and latency, however no amplitude or latency effects of interval were found for infrequent nontargets. Theoretical implications will be discussed. Email: Michelle Brennan:
The Effect of Motivational Relevance on Processes of Attentional Orienting: An ERP Analysis
Kate Briggs and Frances Martin
University of Tasmania, Tasmania, Australia
Abstract: Rapid shift of attention from appetitive and aversive cues to subsequent environmental stimuli are highly adaptive, however there is limited information regarding the effect that motivationally relevant stimuli have on the specific components of covert visual attention as measured by ERP responses. Two experiments were therefore designed to investigate the effect that motivationally relevant stimuli have on processes of attentional engagement and disengagement in a peripheral cueing paradigm. Nineteen females in Experiment 1 and 18 females in Experiment 2 were presented with a modified peripheral cueing paradigm where sexual, mutilation, human threat, and neutral IAPS stimuli served as the peripheral cues. The target evoked P1 and P3 amplitudes in both experiments were enhanced in response to targets cued by sexual and mutilation stimuli regardless of the cued location, and the cue evoked P3 amplitude in Experiment 1 was also significantly enhanced in response to these stimuli. As target processing was facilitated independent of the cued location, it was concluded that the presentation of a motivationally relevant cue does not differentially affect the engagement and disengagement components of covert visual attention, rather the target processing of normal participants is characterised by a global response bias. Email: Kate Briggs:
The Effect of Stimulus Expectancy on ERPs in an Inter-Modal Oddball Task
Christopher Brown, Adam Clarke and Robert Barry
Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: Previous inter-modal oddball studies identified a P300 component elicited by auditory target stimuli in an inter-modal oddball task that differs from P300 to targets in a two-tone oddball task. It was unclear from these studies whether this difference reflected the processing of the auditory target or processes related to the omission of the standard stimulus, which was from a different modality. The purpose of this study was to clarify this question. Twenty subjects carried out four randomly presented tasks, which required auditory target detection. A frequently presented visual stimulus of fixed ISI was randomly interspersed with infrequent auditory tones. Auditory stimuli were presented at the time the frequent stimulus was expected, or 50, 100 or 200 ms after the expected time in the four tasks respectively. Preliminary analysis suggests that delaying the presentation of the target stimulus had little effect on the latency of auditory target ERPs. It also showed that the inter-modal P300 did not differ as a factor of task. This suggests that it is not a reflection of visual stimulus omission. These data provide further evidence for separate P300 components that can be elicited in different stimulus contexts. This is discussed in light of the earlier research. Email: Christopher Brown:
The Functional Significance of P3 in a Response Conflict Paradigm
Samantha Broyd, Stuart Johnstone and Steven Roodenrys
Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: The current study investigated the functional significance of the P3 component within the Eriksen flanker task. In this task, the N2 component is considered an index of response conflict processing, whilst a functional interpretation of the P3 component is less clear. ERP data was examined in 2 experiments (n = 44) using different versions of the Eriksen flanker task. In the first experiment, a central stimulus was surrounded by 2 or 4 distracting stimuli, while the second experiment varied the level of distraction created by the flanking stimuli. Both experiments included neutral, congruent and completely incongruent (CI) trials, while the second experiment also included trials with high (HI) and low (LI) levels of incongruence. A response conflict interpretation of the N2 was supported in both experiments. In contrast, P3 amplitude was reduced in congruent and CI trials relative to neutral trials in the first experiment. In the second experiment P3 amplitude was reduced in HI and LI trials relative to neutral, with larger P3 amplitudes in CI than HI trials. The findings suggest that the P3 component may be independent of response conflict processing and instead may reflect the level of discriminability of the target stimuli. Email: Samantha Broyd:
Ear Temperature, Blood Flow, and Cognition
Nicolas Cherbuin and Cobie Brinkman
The Australian National University, Canberra, Australia
Abstract: Complex measures of cerebral activation are not always available, affordable or practical. In some experimental conditions (e.g. emotions, functional lateralization) the main variable of interest or a covariate may be whether the left or right hemisphere is more active during a task. We have investigated functional tympanic membrane thermometry (fTMT) as an index of hemispheric lateralization and found that continuous ear temperature measurement can be used as a broad measure of hemispheric activation. Email: Nicolas Cherbuin:
Clinical Utility of the Brain Resource International Database of Brain and Cognitive Function: Case Study Examples
C. Richard Clark
School of Psychology, Flinders University, Melbourne, Australia
Abstract: The Brain Resource International Database (BRID) established over the past five years (e.g. Gordon et al., 2005) provides an important multimodal and integrative approach to understanding brain and cognitive function in health and disease. The many investigations from this database recently published in the literature have effectively established its sensitivity to demographic factors on a range of integrative measures (e.g. Clark et al, 2006). Thus, it is not surprising that the database is playing an increasing role in clinical investigations of abnormal function. This paper will review elements of its high sensitivity and provide medicolegal case examples of its provision of psychobiological evidence of brain and cognitive dysfunction under conditions where behavioural neuropsychological evidence of dysfunction alone might be deemed equivocal. Email: C. Richard Clark:
Effects of Stimulant Medications on the EEG of Girls With Attention-Deficit/Hyperactivity Disorder
Adam Clarke,1 Robert Barry,1 Rory McCarthy,2 Mark Selikowitz2 and Stuart Johnstone1
1Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
2Sydney Developmental Clinic, University of Sydney, Sydney, Australia
Abstract: Stimulant medications are the most commonly-used treatments for Attention Deficit Hyperactivity Disorder (AD/HD) in North America and Australia, although it is still not entirely known how these medications work. This study investigated the effects of stimulant medications on the EEG of girls with AD/HD, an under-explored population. An initial EEG was recorded during an eyes-closed resting condition, with data Fourier transformed to provide absolute and relative power estimates for the delta, theta, alpha and beta bands. Subjects were placed on a six month trial of a stimulant and a second EEG was recorded at the end of the trial. The unmedicated girls had significantly greater total power, absolute delta and theta, more relative theta especially in the frontal regions, and reduced frontal relative delta and beta activity compared with controls. The stimulant medications resulted in a normalisation of the EEG, with changes primarily occurring in the delta, theta, and beta bands. These results suggest that stimulant medications may have their therapeutic effect by improving processing deficits in these children as opposed to increasing arousal levels. Email: Adam Clarke:
The Repetition Positivity: An Index of Echoic Memory Formation?
Rowena Cooper, Pat Michie and Juanita Todd
Functional Neuroimaging Laboratory, University of Newcastle, Newcastle, Australia
Abstract: The Repetition Positivity (RP) is a newly described event-related potential (ERP) component thought to represent brain processes involved in the development of an auditory sensory memory trace (Baldeweg et al., 2004; Haenschel et al., 2005). RP was observed within an auditory oddball paradigm that had a ‘roving’ standard. In this paradigm the frequently occurring standard sound is roving in the sense that it changes in pitch every time an infrequent deviant sound is played. The RP is a positive component which increases in positivity as the number of repetitions of the standard tone increases and which overlaps the latency period of several components in the standard ERP plus mismatch negativity (MMN). Previous research has shown that older adults elicit reduced MMN amplitude. This result has been used to infer that auditory sensory memory functioning changes as we age. However, RP may be a more direct way of assessing age-related changes in auditory sensory memory formation. Using four repetition conditions with 4, 8, 16, or 24 standards preceding each deviant we found a significant effect of repetition (RP) in a group of 25 young adults. Preliminary results from a group of older adults will also be presented. Email: Rowena Cooper:
Does Glycine Augment MMN in Healthy Controls?
Rodney Croft,1 Sumie Leung,1 Barry O’Neill1 and Pradeep Nathan2
1Swinburne University, Melbourne, Australia
2Monash University, Melbourne, Australia
Abstract: Mismatch negativity (MMN) is an event-related potential component that has been consistently found deficient in schizophrenia. It is thought that MMN indexes glutamate function, and consistent with this finding glutamate augmentation (using glycine) has been trialled as an adjunct therapy in schizophrenia. Due to the heterogeneity of the disorder (some schizophrenics may not have impaired glutamate function), it is important to ascertain whether glycine has a positive effect on a normal glutamate system. The present study thus tested whether glycine would improve healthy controls’ MMN. A duration-deviant MMN protocol was administered to 16 participants under placebo and 0.8g/kg glycine conditions, using a repeated-measures double-blind placebo-controlled design. Four participants are yet to be analysed. Preliminary results show a reduced MMN amplitude across frontal sites in the glycine condition (F[1,11]=5.87; p=0.034), with no effect at mastoid locations. The results suggest that in healthy participants, MMN amplitude is reduced rather than enhanced with 0.8g/kg glycine. This in turn suggests that care needs to be taken to select those patients with glutamate impairment for glycine adjunct therapy, rather than employing this treatment uniformly for all schizophrenia patients. Email: Rodney Croft:
Target-To-Target Interval Effects on P300: Implications for Expectancy Theory
Craig Gonsalvez and Robert Barry
Brain & Behaviour Research Institute,
University of Wollongong, Wollongong, Australia
Abstract: The relationship between P300 amplitude and target stimulus probability has been extensively examined and is well established. Larger amplitudes are obtained with low target probability in auditory, visual, and somatosensory modalities. Despite the consistent empirical results, the exact reason for P300 effects in oddball tasks is unclear and vigourously debated. For example, low-probability targets may elicit larger P300 amplitudes because of memory updating processes associated with decreased expectancy (context update, Donchin & Coles, 1988). Alternatively, low probability targets are actually expected, with larger P300 amplitudes reflecting resolution of a state of suspense (context closure, Verleger, 1988). More recently, a series of studies has demonstrated fairly conclusively that target-to-target interval (TTI), not probability, is the critical determinant of P300 amplitude in oddball tasks. These results appear inconsistent with context update predictions, but do they support context closure? Previous TTI studies have focused mainly on P300 amplitude, but a coherent account involving P300 latency and RT data has not been presented. The current presentation draws upon data from a large number of studies to argue that neither of the theoretical positions is viable and that it may be time to divorce P300 theory from its expectancy heritage. Email: Craig Gonsalvez:
ERP and fMRI Correlates of Anticipatory Task Set Reconfiguration
Sharna Jamadar,1,2 Frini Karayanidis,1,2 Ross Fulham,1 Matthew Hughes1,2 and Pat Michie1,2
1Functional Neuroimaging Laboratory, University of Newcastle, Newcastle, Australia
2Neuroscience Institute for Schizophrenia and Allied Disorders
Abstract: Task switching involves rapid alternation between simple tasks and results in larger reaction time for switch than repeat trials. Our lab has previously demonstrated an ERP correlate of preparation to switch task, and the present study investigated fMRI correlates of this effect. Twenty-four participants switched between a letter task and a digit task. Behavioural, ERP, and event-related fMRI data were collected. Switching with anticipatory preparation was associated with increased switch positivity in cue-locked ERP waveforms, as expected. Switching with preparation was also associated with an increase in activation in the precuneus, superior parietal lobule and precentral gyrus (all p<.01). Behavioural switch cost was correlated with increased activation in the superior and middle frontal gyri, inferior parietal lobule and postcentral gyrus (all p<.001). Mean amplitude of the ERP switch positivity was correlated with activation in the precuneus and postcentral gyrus (all p<.001). Switching with anticipatory preparation is associated with increased positivity in switch relative to repeat ERP waveforms. Furthermore, prepared switching also appears to activate a network of parietal regions. Activation in some of these regions is correlated with the behavioural switch cost and ERP switch positivity. Email: Sharna Jamadar:
Response Inhibition During a Stop-Signal Task in Two Subtypes of AD/HD
Stuart Johnstone, Robert Barry and Adam Clarke
University of Wollongong, Wollongong, Australia
Abstract: Children with AD/HD of the Combined Type (AD/HDcom) have problems with response inhibition, with poorer task performance and atypical inhibition-related ERPs relative to controls, while little is known about this process in children with AD/HD of the Predominantly Inattentive Type (AD/HDin). Here children with AD/HDin (N=12), AD/HDcom (N=13) and age-matched controls (N=13) aged between 8 and 14 years completed a Stop-signal task while EEG was recorded. No inhibitory performance differences were found, but the AD/HD groups showed more errors of Omission to Go stimuli than controls. Go ERPs differed between children with AD/HDin and controls, while the AD/HDcom group showed only minor scalp distribution differences (N2 and P3). The AD/HDin group showed across Trial Type magnitude differences from controls to Stop-signals (central N1 and parietal P3; midline N2) and failed to show a Successful vs. Failed inhibition effect for P3. The AD/HDcom group showed reduced parietal P3 across Trial Types, with the Trial Type effect present for N2 but not P3. These data suggest that the apparent atypical inhibitory processing at N2 and P3 may stem, at least in part, from atypical early sensory/alerting processing of all stimuli in children with AD/HDin. Email: Stuart Johnstone:
Stop-Signal Inhibition in Two Subtypes of AD/HD
Stuart Johnstone, Robert Barry and Adam Clarke
University of Wollongong, Wollongong, Australia
Abstract: This study examines response inhibition in children with AD/HD of the Predominantly Inattentive Type (AD/HDin). Children with AD/HDin (N=12), AD/HDcom (N=13) and age-matched controls (N=13) aged 8-14 years completed a Stop-signal task while EEG was recorded. No inhibitory performance differences were found, but the AD/HD groups showed more errors of Omission to Go stimuli. Go ERPs differed between children with AD/HDin and controls, while the AD/HDcom group showed only minor scalp distribution differences (N2 and P3). The AD/HDin group showed across Trial Type magnitude differences from controls to Stop-signals (central N1 and parietal P3; midline N2) and failed to show a Successful vs. Failed inhibition effect for P3. The AD/HDcom group showed reduced parietal P3 across Trial Types, with a Trial Type effect for N2 but not P3. These data suggest that the apparent atypical inhibitory processing at N2 and P3 may stem, at least in part, from atypical early sensory/alerting processing of all stimuli in children with AD/HDin. Email: Stuart Johnstone:
Reaction Time Facilitation by Acoustic Task-Irrelevant Stimuli is Not Related to Startle
Ottmar Lipp,1 Daniel Kaplan2 and Helena Purkis1
1University of Queensland, Queensland, Australia
2Washington University
Abstract: Previous research has been interpreted to suggest that the startle reflex mediates the RT facilitation observed if intense, accessory acoustic stimuli are presented coinciding with the onset of a visual imperative stimulus in a forewarned simple RT task. The present research replicated this finding as well as the facilitation of startle observed during the imperative stimulus. It failed, however, to find any relationship between the size of the blink startle reflex elicited by the accessory acoustic stimuli, which differed in intensity and rise time, and RT or RT facilitation observed on trials with accessory acoustic stimuli. This finding suggests that the RT facilitation is not mediated by the startle reflex elicited by the accessory acoustic stimuli. Email: Ottmar Lipp:
Is There Interaction Between Sound Frequency and Ear of Presentation Effects on MMN Amplitude in Dichotic Paradigms?
David N. McKenzie and Robert J. Barry
Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: Rapid dichotic presentation involves simultaneously playing two trains of tones: a higher frequency (HI) train to one ear and a lower frequency (LO) train to the other ear. Some experiments reverse the ear of presentation of the trains in half of their blocks. Other experiments present only one train (i.e. one frequency) to a given ear throughout. These techniques were compared for their effect on duration- and frequency-MMN amplitude. Eleven right-handed and 10 left-handed participants listened to a dichotic oddball presentation. Standard sounds (all 50 ms; 2000 Hz and 70 dB SPL to one ear, 800 Hz and 85 dB SPL to the other) were mixed with occasional frequency deviants (5% increase) and duration deviants (100 ms). Participants attended to one ear per block. For half of the 20 blocks presented, the headphones were reversed. Thus, each ear received HI and LO sounds. Duration- and frequency-MMN amplitudes were each separately analysed for attended and unattended sounds. Sound frequency effects did not interact significantly with either ear of presentation or participant handedness effects for MMN amplitude. The pattern of duration- and frequency-MMN amplitude is unaffected by the balancing of sound frequency presented in dichotic presentations. Email: David McKenzie:
Rapid Naming and Magnocellular Function in Adult Reading Fluency
Isobel McKinnon,1 David Crewther1 and Sheila Crewther2
1Swinburne University of Technology, Melbourne, Australia
2La Trobe University, Melbourne, Australia
Abstract: Deficits in rapid visual processing in reading disabilities (RD) may be due to problems in temporal processing relying on visual magnocellular pathways, resulting in an inability to quickly disengage attention from one stimulus and move on to the next. In this study of 24 non-dyslexic individuals from a range of reading skills, reading performance on tasks involving continuous rapid naming and discrete rapid naming were compared with components of the second order kernel of the multifocal flash visual evoked potential (mfVEP) previously shown to be associated with magnocellular and parvocellular visual inputs. Although there was a difference in performance on continuous rapid naming between good and poor readers, this relationship was not mediated by magnocellular functioning. However, a novel relationship between the parvocellular evoked response and non-verbal mentation was discovered. Implications of these findings are discussed with respect to similar studies in children with dyslexia. Email: David Crewther:
The Pharmacology of the Loudness Dependence of Auditory Evoked Potentials
Barry O’Neill,1 Rodney Croft1 and Pradeep Nathan2
1Brain Sciences Institute, Swinburne University, Melbourne, Australia
2Monash Centre for Brain and Behaviour, Monash University, Melbourne, Australia
Abstract: To date, methods for measuring serotonin in the brain are circuitous in that they measure indirect constructs such as behavioural changes or neurochemical concentrations overall, and none are able to measure serotonergic activity as it occurs in the brain. A valid means of assessing brain serotonin function may be useful for diagnosis of psychiatric conditions and possible pharmacological intervention, and the loudness dependence of auditory evoked potentials (LDAEP) has been proposed as such a measure. While there is some evidence that supports the validity of this measure, there is also evidence suggesting that it may not be specific to the serotonin system. In order to help clarify the relative specificity of the LDAEP to serotonin, we conducted a series of double-blind, repeated-measures, placebo-controlled studies, augmenting dopamine and glycine levels, and depleting dopamine, serotonin and combined dopamine/serotonin levels. These results will be presented and discussed in terms of the evaluation of the validity of the LDAEP as a measure of central serotonergic function. Email: Barry O’Neill:
Interference Control in Children With AD/HD: An ERP and Behavioural Analysis
Sarah Opychane and Stuart Johnstone
University of Wollongong, Wollongong, Australia
Abstract: Behavioural studies report that children with AD/HD are more susceptible to the interfering effects of distractors than control children, though few studies have considered the neural bases for these overt differences. This study examined interference control in children with AD/HD using the Flanker Task. Event-related potentials (ERPs) and skin conductance level (SCL) were recorded from 20 children with AD/HD and 21 control children, aged between 7-14 years. Across group, there was an increase in errors and RT to incongruent trials. Children with AD/HD made more choice errors to incongruent and congruent trials than controls. ERP effects revealed a larger centro-parietal P3 to incongruent stimuli, but no condition effect on the late N2 amplitude. There was a larger P3 to congruent trials in control than the AD/HD group. Behavioural data support an interference control deficit in children with AD/HD. The larger P3 is suggestive of increased effort and attention to dual response activation and the lack of late N2 amplitude modulation may reflect increased sensitivity to distractors. Interaction effects suggest reduced attention to congruent trials in children with AD/HD, reflected in the increased errors in this condition relative to controls. Email: Sarah Opychane:
ERP and Behavioural Correlates of Genuine and Posed Facial Expression Discrimination
Mark Ottley, John Dalrymple-Alford, Lucy Johnston, Lynden Miles and Tracey McLellan
University of Canterbury, New Zealand
Abstract: The ability to recognise an individual’s affective state by their facial expression is crucial to human social interaction. However, our understanding of facial expression discrimination processes remains limited. The situation is complicated by mounting evidence indicating that there are important differences between genuine and posed facial expressions. Posed expressions are easier to recognise than genuine expressions, less symmetrical, composed of different facial action unit components, and are differentially discriminated by observers. Despite this most previous studies of facial expression discrimination have used posed or simulated facial expressions as stimuli. The current study compared behavioural and ERP responses generated in covert and overt viewing tasks, of genuine smile expressions, posed smile expressions and neutral expressions. Different expressions were differentially discriminated by participants. Affective happiness was more likely to be attributed to persons displaying genuine smiles than to persons displaying posed smiles. Analysis of ERP data revealed a large attentional effect of task on the face specific N170 ERP component for the overt versus covert conditions. Further detailed analysis of other ERP components is being undertaken. Email: Mark Ottley:
Facial Emotion Processing from Childhood to Adulthood: An Event-Related Potential Study of Maturational Changes
Donna M. Palmer,1 Belinda J. Liddell,1 Evian Gordon1,2,3 and Leanne M. Williams1,2,4
1The Brain Dynamics Centre, Westmead Millennium Institute, Westmead Hospital, Sydney, Australia
2Psychological Medicine, Western Clinical School, University of Sydney, Westmead Hospital, Sydney, Australia
3Brain Resource International Database, Brain Resource Company, Sydney, Australia
4School of Psychology, University of Sydney, Camperdown, Australia
Abstract: The interpretation of facial expressions of emotion is important for successful social interaction. This study examines maturational changes in the ERP waveform in response to facial emotion, from middle childhood to young adulthood. 322 healthy subjects (6 to 30 years) were included in this study, acquired in collaboration with the Brain Resource International Database. EEG recordings were acquired while subjects viewed faces displaying various emotional expressions, from which ERPs were extracted. Maturational changes in the effects of emotion processing differed markedly between brain regions. Age-related changes were observed in the time course of facial emotion processing over frontocentral regions, while the effects of emotion processing remained comparatively stable over occpito-temporal regions. Frontocentrally, the youngest subjects displayed emotion processing effects very early in the time course. By late childhood these effects shifted to the later period of the time course, particularly apparent in the slow wave occurring 300-700ms post-stimulus. These effects of emotion processing shifted again from early adolescence onwards, becoming most evident in the components occurring 150-400ms post-stimulus, as observed in the adult ERP waveform. These findings are interpreted in the context of overarching changes in brain structure and function that also occur across this maturational period. Email: Donna Palmer:
Magnetoencephalography Demonstrates Recurrent Processing in the Posterior Parietal and Visual Cortex in Response to Cued and Uncued Visual Search
Kristen Pammer,1 Johanna Uusvuori2 and Riitta Salmelin2
1School of Psychology, The Australian National University, Canberra, Australia
2Low Temperature Laboratory, Helsinki University of Technology, Helsinki, Finland
Abstract: An emerging theme in the attentional literature is the role of extra-striate cortical responses in modulating early visual processing. This has been investigated primarily by using inter-cell recordings, which is highly invasive, or fMRI which lacks the temporal resolution to clearly identify the time course of information flow and thus re-entrant feedback loops. Here magnetoencephalography is used to measure cortical responses to cued and uncued visual search in humans to determine the role of the dorsal stream in attentional shifting. Dipoles modelled within 400ms of target onset at the right posterior parietal cortex (PPcR), visual cortex and left/right inferior temporal regions demonstrated recurrent peaks of activity, implying modulatory feedback loops. Moreover, the PPcR consistently demonstrated the earliest activation, typically less than 100ms, and before activation in the visual cortex, supporting the suggestion that the dorsal stream is involved in voluntary orienting by ‘priming’ the visual system to be responsive to the following target stimulus. Email: Kristen Pammer:
Can Transcranial Doppler (TCD) Measures of Cerebral Arterial Blood Flow Reflect Brain Activation?
Catherine Paul, Neva Bull and Mick Hunter
School of Psychology, University of Newcastle, Newcastle, Australia
Abstract: Functional transcranial Doppler (fTCD) is a non-invasive ultrasound technique that can measure blood flow velocity in the major cerebral arteries. The technique has been used successfully to assess hemispheric dominance of cognitive functions and to look at temporal dynamics of a response to a stimulus. A relatively recent use of fTCD is to localise cortical functions within arterial territories. While research into this is new, there has been some promising results. The current study uses fTCD in an attempt to localise cortical functions involving motion and form visual processing. The results are discussed in terms of the capacity of relative blood velocity measures to discriminate activation patterns. Email: Mick Hunter:
Event-Related Potentials and Behavioural Performance in Attention-Deficit/Hyperactivity Disorder: Aiding in Diagnosis or Adding to Ambiguity?
Sharnel Perera,1 David Crewther,1 Rodney Croft,1 Daniel Hermens,2 Simon Clarke2 and Lea Williams2
1Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
2The Brain Dynamics Centre, Westmead Hospital, Sydney, Australia
Abstract: Electrophysiological measures have been used extensively in AD/HD research to describe, assess, and quantify its symptomatology and treatment response. The present study focuses on the possibility of utilising EEG, specifically ERPs, and behavioural performance in aiding AD/HD diagnosis, at both clinical and subtype levels. Using a two-tone Oddball task, data from two subtypes of AD/HD (AD/HD-in and AD/HD-com) and age-and gender-matched controls were obtained; Reaction Time, reaction time variability, False Positives, and False Negatives to targets were obtained along with ERPs N1, N2, and P3 from midline sites Fz, Fz, and Pz respectively. Data were analysed via a Logistic Regression due to violation of the normality assumption. When incorporating ERPs and behavioural performance data, the present study was able to distinguish AD/HD subjects from Controls with an accuracy of 75.9%, Controls from AD/HD-com with 69.8% accuracy, Controls from AD/HD-in with 74.7% accuracy, and AD/HD-in from AD/HD-com with 63.9% accuracy. ERPs in conjunction with behavioural performance data show some promise in aiding in the preliminary diagnosis of AD/HD, however the possibility of it aiding in subtype diagnosis is still questionable due to the considerably larger margin of error. Email: Sharnel Perera:
Unattended Sound Representations Are Not Streamed But May Be Merged: Evidence From MMN
Kane Pfingst and David McKenzie
University of Newcastle, Newcastle, Australia
Abstract: Previous attempts (Sussman, Ritter and Vaughan, 1998; 1999) using the mismatch negativity (MMN) to resolve the role of attention in auditory streaming are criticised for poor control of attention. MMN, an attention-independent component of an event-related potential, is elicited by occasional deviant sounds mixed in a repetitive auditory stimulation, and indexes the sensory processing of acoustic sources. We investigated the necessity of attention for streaming using the MMN and rapid dichotic presentations to control attention. Two conditions of four tone sequences (1000 and 1200 Hz to one ear; 2000 and 2400 Hz to the other) were dichotically presented. Twenty participants attended the lowest frequency source in a designated ear, and responded to frequency deviants so the other three sources were unattended. All sources had occasional 150 ms duration deviants tones. All sources had repeated 100 ms standard tones in one condition. The two high-frequency, unattended sources were replaced with 40 ms standards in the other condition. The MMN latency relative to the unattended 100 ms standards changed between the two conditions. The MMN latency relative to the attended 100 ms standards did not change. These results show attention is required for auditory streaming and MMN can operate on merged representations. Email: Kane Pfingst:
Is Ocular Voltage Propagation to the EEG Frequency Dependent?
Trieu Pham,1 Rodney Croft,1 Peter Cadusch2 and Robert Barry3
1Brain Sciences Institute, Swinburne University, Melbourne, Australia
2Department of Life and Social Sciences, Swinburne University, Melbourne, Australia
3Department of Psychology, University of Wollongong, Wollongong, Australia
Abstract: There are currently several EOG correction methods that subtract a portion (propagation coefficient) of eye movement voltage from the EEG. Some of these use different propagation coefficients for different frequencies of EOG/EEG, and others treat propagation coefficients as being frequency independent. In order to determine whether propagation coefficients are frequency dependent, and whether such frequency dependence is due to varying signal-to-noise ratios SNRs, trials of different eye movement types (saccades and blink) were collected and analyzed separately for different frequency bands (ranging from 0-40Hz), and eye movement ERPs created with different SNRs (n=1, 5, 10, 25, 50, 100, 150, 200). Propagation coefficients were then calculated for each of the above ERPs, for each frequency band. Eight participants’ data were recorded, and no evidence of frequency dependence was found for either vertical (p=0.13) or horizontal saccades (p=0.78), nor was there any evidence of an effect of SNR on this frequency ‘independence’ (p>0.24). These results suggest that propagation coefficients are not frequency dependent, and that SNR (as manipulated in the current study) does not affect this finding. This suggests that frequency domain approaches to EOG correction are not appropriate. Email: Trieu Pham:
Effects of Flavonoids on Brain Functional Connectivity During a Recognition Memory Task
Andrew Pipingas and Richard Silberstein
Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
Abstract: Dietary supplementation with plant extracts rich in flavonoids is becoming popular for its potential health benefits yet relatively little research has been conducted to investigate effects on neurological cognitive function. This study investigated effects of supplementation with a Pinus Radiata bark extract (Enzogenol¨) and vitamin C (vitC) on brain functional connectivity during the performance of a recognition memory task. Previously, we found that supplementation with Enzogenol improves speed of response during spatial working memory and recognition memory performance. Forty-two men (50-65 years) were enrolled in the study. Participants were randomly selected to supplement with either Enzogenol and vitC or vitC alone for 5 weeks. Brain electrical activity was recorded while subjects performed a recognition memory task. Steady-state visually evoked potential (SSVEP) - event-related partial coherence (ERPC) measures were calculated and compared before and after supplementation for each group. Prior to supplementation, comparison of correct items and incorrect items was associated with decreased SSVEP-ERPC at approximately 700ms following item presentation. Supplementation with Enzogenol + vitC but not vitC alone was associated with decreased fronto-parietal SSVEP-ERPC at approximately the same time following item presentation. These findings are consistent with the hypothesis that Enzogenol enhances brain mechanisms mediating memory processes. Email: Andrew Pipingas:
Separation of the Components of the Late Positive Complex in an Active vs. Passive Auditory Oddball Task
Jacqueline Rushby and Robert Barry
Brain & Behaviour Research Institute and School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: A resurgence in the use of decomposition techniques, such as PCA, shows that two sub-components, the P3b and the P3a, are elicited to deviant stimuli in the oddball task. An additional sub-component, the classic SW, is also elicited for some active conditions. We recently examined the sub-components of the LPC in an ERP dishabituation paradigm (Rushby et al. 2005). In contrast to the oddball literature we found evidence for four separate components, the P3a, P3b, Novelty P3 and SW. For the current study we examined response requirement (passive versus button press) and intensity (loud versus soft) effects in different groups. Only one block of stimuli (102 frequent, 18 deviant) was presented. Again, in contrast to current oddball literature, four separate components were extracted, again corresponding to the P3a, P3b, Novelty P3 and SW. The findings for the P3b and SW components are in agreement with the literature. The P3a component, however did not differentiate response requirements, and was elicited only when the deviant was an increment in intensity. The Novelty P3 was of similar magnitude to all deviant types. These stimulus-response patterns exhibited by the LPC sub-components will be discussed from an Orienting Reflex perspective. Email: Jacqueline Rushby:
Brain Functional Connectivity Changes During a Working Memory Task: Aptitude and Gender Effects
Richard Silberstein,1 Cindy Van Rooy2 and Geoffrey Nield3
1Brain Sciences Institute, Swinburne University of Technology, Melbourne, Australia
2Australian Drug Foundation
3Neuro-Insight Pty Ltd
Abstract: Cognition related changes in brain functional connectivity are mediated by synchronous oscillations. We suggest that such functional connectivity is also reflected in 13 Hz steady state visually evoked potential partial coherence. In this presentation we discuss changes in functional connectivity during performance of the 2-back verbal working memory task where 62 subjects (43 females) were presented with a random sequence of letters and had to identify the appearance of a target letter comprising the re-appearance of a letter previously presented 2 letters back. The appearance of a letter was associated with transient increased parieto-occipital coherence followed by a reduction in prefrontal coherence. In the subsequent epoch where subjects held the letter sequence in working memory, we observed transient increases in prefrontal coherence. There were no significant gender differences in task related functional connectivity. When we correlated individual speed or accuracy with coherence we observed a time dependent positive correlation between task speed and coherence and a negative time-dependent correlation between task accuracy and coherence. These correlations were only observed in the male population. The significance of task dependent changes in functional connectivity will be discussed as well as gender differences in the coherence correlates of individual aptitude. Email: Richard Silberstein:
Sense of Effort in Static Exercise
Janette Smith, Janet Taylor, Peter Martin, Rachel McBain and Jane Butler
Prince of Wales Medical Research Institute, Sydney, Australia
Abstract: The sense of effort in performing exercise may be generated by central command or afferent feedback. If effort is related to motor output or afferent feedback, then if muscular work is doubled, we expect that perceived effort should also double. This study measured the relationship between perceived effort and variables associated with static contractions including force and ventilation. Eight subjects made 10s contractions to 25%, 50% and 100% of maximum force with the left arm, right arm, and both together. Subjects rated the effort needed to produce target forces on an open-ended scale. Effort ratings increased with stronger contractions. However, effort with 2-armed contractions was only ~120% of that for matching1-armed contractions. Similarly, exercise-induced increases in ventilation correlated with contraction strength, but were not different for 1-armed and 2-armed contractions. In another experiment, subjects made contractions with the arm alone, leg alone, and arm and leg together, with similar results. The study shows a strong relationship between perceived effort and ventilation, with neither strongly related to the total muscle work. This suggests that neither sensory input nor corollaries of descending output from the motor cortex underlie the sense of effort or the ventilatory response to exercise. Email: Janette Smith:
An EEG Investigation of the Dissociated Control Model of Hypnosis
Kate Stone,1 Joe Ciorciari,1 Rodney Croft1 and Colin Carbis2
1Swinburne University, Melbourne, Australia
2Virtual Medicine, Melbourne, Australia
Abstract: This study investigated EEG magnitude coherence changes in healthy volunteers; 14 low in hypnotic susceptibility and 4 moderate. Hypnosis was induced using an audio-visual ‘virtual reality’ hypnosis tool. Coherence was calculated between Fz and F7, and Fz and F3 electrodes. This was thought to reflect synchronous activity between anterior cingulate and prefrontal cortex. Significant changes were not seen from baseline to hypnosis conditions, however notwithstanding the small sample size, decreases in coherence that approached significance were seen in moderate hypnotisables during hypnosis but not in lows. These findings show a trend in line with previous research demonstrating that high hypnotisables experience frontal dissociation in hypnosis. Further research using a larger sample including high hypnotisable subjects is required to give support to the dissociated control model of hypnosis. Email: Kate Stone:
Psychophysiological Examination of Addiction and Level of Engagement in Potentially Addictive Behaviours
Naomi Thomas and Frances Martin
School of Psychology, University of Tasmania, Tasmania, Australia
Abstract: Research suggests behavioural addiction exists on a continuum ranging in severity from non-disordered engagement to pathological use leading to neuronal adaptation and negative psychological and social consequences. This study was the first to employ a psychophysiological measure to examine the existence of engagement and addiction along a continuum for potentially addictive behaviours; specifically gambling, computer games, coin-operated video-arcade games and the Internet. A visual three-stimulus oddball task, used to elicit the P3b component, was completed by 80 participants aged 17-28. Three continuum hypotheses were investigated; engagement only, engagement and addictive symptoms, and continuum of addictive experience ranging from no clinical symptoms to addiction. It was hypothesised that P3b amplitude, which indexes the cognitive resources devoted to a task, would be sequentially reduced in participants with progressively greater engagement and addictive symptoms. Findings indicate that P3b amplitude discriminated between levels of engagement, progression of addictive symptoms and engagement, and continuum of addictive symptoms, particularly at midline sites. Consistent with past research investigating substance addiction, these findings suggest that participants with lower levels of engagement and no addictive symptoms had more resources available to perform the task than subjects with either a subclinical level of addictive symptoms or diagnosis of addiction. Email: Naomi Thomas:
The Emotional Stroop Effect in Panic Disorder: An Electrophysiological Study
Susan J. Thomas, Craig J. Gonsalvez and Stuart J. Johnstone
Brain & Behaviour Research Institute, School of Psychology,
University of Wollongong, Wollongong, Australia
Abstract: In emotional Stroop tasks, individuals with panic disorder show delayed response times (RTs) when asked to name the colour of words related to their specific fears. Cognitive theories assume that this ‘emotional Stroop’ effect is related to attentional biases, which are important to the development of anxiety. RT studies alone have been inconclusive in determining the nature or information processing locus of attentional biases, as they employ no direct measure of attention to threatening stimuli. We used event-related potentials (ERPs) to more directly examine the emotional Stroop effect in panic disorder. Fourteen individuals with panic disorder, and 22 healthy controls, participated. ERPs and RTs to high threat, low threat and neutral words were recorded during two tasks (colour relevant, in which the colour ink of words was identified, and word relevant in which words were classified as threatening or not). Only the panic group showed delayed RTs to colour name personally threatening words. Between group differences were also observed in ERPs to threat-neutral stimuli. ERPs help elucidate the nature of attentional biases to threatening information in emotional Stroop tasks. The patterns of differences between individuals with panic and normals, and their clinical implications are discussed. Email: Susan Thomas:
EEG Spectral Dynamics During Visuo-Motor Imagery
Zoe Thayer and Blake Johnson
Research Centre for Cognitive Neuroscience, University of Auckland, Auckland, New Zealand
Abstract: We addressed the question of whether the primary motor cortex is directly involved in mental rotation. A task was used which ensured implicit motor imagery to investigate the neural activity of motor structures. Sixteen healthy participants performed handedness judgments of visually presented hands. Our design ensured subjects performed mental rotation of every stimulus but in half the trials made no behavioural response. The EEG spectral perturbations showed that the visual stimulus elicited alpha-band desynchronisation at posterior electrodes within 200 ms of stimulus onset, with resynchronization after stimulus offset. Beta-band responses in parietal electrodes were associated with mental rotation during a time window of 500-1000 ms; and beta-band responses at central electrodes were associated with preparation for and emission of the behavioural response as early as 300 ms. Mu-band responses over sensorimotor cortex were associated only with the overt response. Our data suggest that activations of motor cortices during a mental rotation task are associated with the emission of the behavioural response but are not directly associated with the neural computations underlying mental rotation. Email: Zoe Thayer:
The Relationship of Inhibition and Error Detection to Schizotypal Personality Traits
David Van der Weyde, Arnstein Soyland, Matthew Hughes and Pat Michie
School of Psychology, University of Newcastle, Newcastle, Australia
Abstract: The aim was to assess differences in inhibitory control and error detection as a function of schizotypy using the stop-signal task. Inhibitory control was measured using a new method of inhibitory assessment, the probability curve, and error detection was assessed using the stop-signal N2. Schizotypy was measured in 17 participants using the Schizotypal Personality Questionnaire (SPQ) (Raine, 1991) and inhibition difficulty was parametrically manipulated by presenting stop-signals at three probabilities. By anchoring performance of participants at the highest probability, and holding stop-signal delay (SSD) constant within subjects, variations in inhibitory performance should reflect differences in inhibitory control. Stop-signal reaction time was unrelated to the degree of schizotypy. Variations in inhibitory performance were mainly attributable to changes in Go reaction time, however, there was evidence of different strategies used by high and low schizotypal individuals. Difference in N2 amplitude for successful and unsuccessful inhibition trials was found to correlate negatively with total SPQ score and the Cognitive/Perceptual factor score. Although the results are not in accordance with predictions, it is possible that high SPQ scorers exerted more cognitive effort to perform the stop signal task to criterion, thus showing a greater difference in N2 amplitude. Email: Pat Michie:
The Effect of Attention and Deviance Magnitude on the Amplitude and Latency of the Duration Mismatch Negativity
Lisa Whitson, David McKenzie and Joshua Hay
University of Newcastle, Newcastle, Australia
Abstract: Mismatch negativity (MMN) is a component of an event related potential (ERP) elicited by the brain in response to the presentation of an infrequent deviant stimulus within a sequence of frequent, homogenous standard stimuli. Whether MMN is affected by attention, and at what stage of processing attention exerts its influence has been a contentious for a number of years. The current study sought to demonstrate that attentional modulation of MMN occurs at early sensory stages by demonstrating an interaction between attention and deviance magnitude. Twenty-one participants completed a task involving rapid-dichotic presentation of infrequent longer duration sounds presented amidst a sequence of shorter duration sounds, which elicited the duration mismatch negativity (MMN) component. A main effect of attention and deviance magnitude was found for both amplitude and latency values of the duration MMN. An interaction between the two factors was found for the amplitude values of duration MMN, however, this was marginally non-significant for the latency values. The implications of the results are discussed in terms of an early effect of attention on the duration MMN, which is inconsistent with one interpretation of Naatanen’s (1991) argument that attention will only exert influence on the output of the putative MMN comparison process. Email: Lisa Whitson:
