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Journal of Clinical EEG & Neuroscience, July, 2008ABSTRACTS 17th Annual Conference of the Australasian Society for Psychophysiology Brisbane, Australia, December 7-9, 2007Continuous Input in a Task is Not Necessary in Determining Modality Specificity of Attentional Startle Eyeblink Reflex ModulationPrevious studies in attentional startle modulation have yielded evidence of modality specificity in continuous performance tasks, and modality non-specificity in trial-structured tasks. This finding is of theoretical interest as modality specificity is indicative of early-selection and modality non-specificity of late-selection attentional mechanisms. A recent study demonstrated modality specificity of attentional startle modulation in three groups of modified continuous performance tasks; continuous, trial-structured, and continuous with a trial structure imposed. It suggested that a brief period on the task was sufficient for the emergence of modality specificity. The current study aimed to investigate whether the continuous nature of a task was indeed critical by assessing attentional startle modulation systematically at different positions in a digit stream. Participants performed a task analogous to the modified trial-structured task, and startles were elicited during the first, third, and fifth digit in 7-digit streams. Evidence of modality specific attentional startle modulation was found at all three target positions in the stream, with smaller blinks during targets than during non-targets. Furthermore, the effect size of this blink inhibition was not different across the three positions. This supports the hypothesis that continuous input is not necessary in determining the nature of the attentional mechanisms engaged. Email: salhadad@psy.uq.edu.au An Event-Related Potential Study of Direct and Indirect Semantic Priming in the Cerebral HemispheresTheories of hemispheric asymmetry for semantic processing suggest that the right hemisphere may be more sensitive to weaker semantic relationships than the left hemisphere. We investigated semantic processing in the left and right hemispheres by recording event-related potentials (ERPs) whilst participants performed lexical decisions to directly related, indirectly related and unrelated prime-target pairs, as well as nonword trials. A stimulus onset asynchrony of 200 ms was utilised for all trials, and a divided visual field paradigm was used for presentation of all stimuli, with primes presented centrally and targets presented to either the left or right visual field. Analysis of reaction times revealed direct and indirect priming effects in both the left and right visual field conditions. Analysis of the ERP data also revealed the presence of an N400 and a late positive complex (LPC) in both the left and right visual field conditions. Whilst direct semantic priming was evident in both the N400 and LPC time windows, indirect semantic priming was only evident in the LPC time window. These findings are interpreted with respect to current theories of semantic priming and cerebral asymmetry in semantic processing. Email: a.angwin@uq.edu.au Separating Arousal From Activation: EEG CorrelatesTwo aspects of energetic state, “arousal” and “activation”, have been conceptualized separately in our laboratory. “Arousal” has been defined as the energetic state at any particular time, and task-related “activation” as the change in state from resting baseline to a task situation. Both are reflected in electrodermal activity and measured by skin conductance level. Our previous studies in this area have indicated that physiological responses to stimuli in a task are dependent on the arousal level at the time of stimulus presentation, rather than the task-related activation. In contrast, cognitive performance on the task is dependent on task-related activation, rather than the current arousal level. The present study aimed to extend this dichotomy in relation to EEG measures. We examined differences between eyes-closed and eyes-open resting states in SCL, and EEG power in the traditional bands. Compared to the eyes-closed condition, the eyes-open condition had a higher level of SCL and reduced global alpha power, both of which we had previously associated with increased arousal. In addition, there were focal changes in the other bands, which we associate with localised cortical activation associated with the processing of visual input. Email: robert_barry@uow.edu.au Event Rate and AD/HD: a Topographic and Preparation Potential Analysis of Response InhibitionIt has been proposed that the poor response inhibition performance of children with Attention-deficit/Hyperactivity Disorder (AD/HD) is related to an inability to regulate their state. This study aimed to examine the effect of state modulation, via manipulation of stimulus event-rate, on response preparation and inhibition in eighteen children with AD/HD, and 18 age- and sex-matched controls. Subjects performed a cued visual Go/No-Go task requiring either response activation or inhibition (30%) to the S2 stimulus (the Go or No-Go) following a cue from S1 (the warning stimulus). Task performance and ERPs to Warning, Go and No-Go stimuli, as well as preparation to the S2, were examined. Findings indicated increased No-Go commission and Warning errors, with corresponding ERP evidence of atypical early sensory/attentional processing of both S1 and S2, and response inhibition as indexed by the No-Go P3 during the fast condition in the AD/HD group. CNV results indicated that atypical preparation/expectancy to S2 in AD/HD. It is concluded that, although a deficit in response inhibition has been proposed at the core of AD/HD, the results of the present study emphasise the key role of state factors on the disorder. Email: npb95@uow.edu.au Event-Related Potentials Associated With Explicit Word Recognition are Affected in Healthy AgeingTo examine the effects of healthy ageing on the electrophysiological correlates of recognition memory, event-related potentials (ERPs) were recorded from 15 young (mean age = 21.73 years) and 15 healthy older adults (mean age = 66.67 years) while they performed a word recognition task with 4-or 8-word study list conditions. At test, participants were required to make old/new judgements to visually presented words. Although there was a trend for young participants to perform more accurately, especially on the long list, these differences only approached significance. Despite this, the N400 old/new effect was found to be significantly reduced (across both list lengths) in the old compared with the young participants. Only the young participants demonstrated an LPC old/new effect; and this was only in the long list condition at F4, suggesting that the LPC old/new effect may be sensitive to age-related cognitive changes specifically under higher memory load conditions. Overall the results indicate that these components may be more sensitive to the deleterious effects of age on recognition memory than behavioural measures of accuracy. The findings relating to the N400 are particularly interesting as the effects of ageing on the N400 from explicit recognition tasks have not been thoroughly explored. Email: m.broughton@psy.uq.edu.au Auditory Processing in a Three-Stimulus Inter-Modal Oddball TaskThis study investigated auditory processing in a three-stimulus inter-modal oddball task. Seventeen participants received 300 stimuli. These comprised 30 target (2000 Hz, 60dB) and 30 non-target (1000Hz, 60 dB) auditory stimuli randomly interspersed amidst 240 presentations of a pattern-reversal checkerboard. ERPs to target and non-target stimuli were compared. Both stimuli produced two early negative components. The N100 showed a trend toward larger amplitudes to non-target stimuli, whilst the N140 component, evident only at frontal sites, did not differ. The P200 also showed a trend toward larger amplitudes to non-targets, due primarily to an enhancement at the vertex. Between 200 and 350 ms post-stimulus the stimuli produced marked differences. Targets produced a large parietally maximal positive complex that included a frontal modulation of the P3a component and modulation of the P3b. In contrast non-targets produced a broad negative shift that resolved into a positivity at around 350 ms. This effect has not been previously reported. These data suggest that rare target and non-target stimuli utilise distinct cognitive processes and the results are interpreted in light of previous inter-modal and intra-modal research. Email: chbrown@uow.edu.au Putative Biomarker of Working Memory Systems Development During Childhood and AdolescenceThe study aimed to identify brain functional indicators of working memory systems development between 6 and 18 years. Event-related potentials (ERPs) were recorded from 251 normally developing children to stimuli requiring the updating of working memory. Cluster analysis of ERP componentry divided the sample into three clusters (mean ages 9, 12 and 16 years), with ascending cluster membership independently associated with improved task-performance. The clusters correspond to periods of gray matter loss and white matter increase observed in developing children, supporting the view that the clusters delineate three key qualitative stages in advancing cognitive capability during the maturation of higher brain systems function. This outcome identifies a biomarker with the potential for assessing abnormalities in the rate of brain development. Email: Richard.clark@flinders.edu.au The EEG of Adults With Attention-Deficit/Hyperactivity DisorderIntroduction: Attention-Deficit/Hyperactivity Disorder (AD/HD) is the most common psychiatric disorder of childhood, but it is becoming increasingly more apparent that more than half the childhood sufferers will continue to manifest symptoms of the disorder as adults. While the EEG of children with AD/HD has been extensively examined, comparatively little research has been conducted into the EEG of adults with the disorder. This study investigated the EEG of adults with AD/HD. Methods: EEG was recorded from 20 adult males with AD/HD and an age- and gender-matched control group during an eyes-closed resting condition. The EEG was Fourier transformed to provide absolute and relative power estimates for the delta, theta, alpha and beta bands. Results: The AD/HD group had significantly less absolute delta and more relative theta, across the entire scalp, than the control group. In absolute beta, the AD/HD group had less power at the midline, and an enhancement in power in the right posterior region. Discussion: These results are similar to those found in children with AD/HD, and suggest the presence of a processing deficit. A right posterior elevation in beta activity was also found, which could be related to the ongoing presence of reading disabilities in these subjects. Email: aclarke@uow.edu.au A Neurophysiological Investigation of Word Learning for Familiar and Novel Objects in AdultsEight healthy adult participants were taught new names for familiar and novel objects over 5 sessions in a week. Lexical acquisition was subsequently tested by recording EEGs during a repetition priming paradigm, where a familiar object picture (e.g. tree) was followed by (a) its corresponding name (e.g. tree), (b) an incongruent word (e.g. brick), (c) a nonword learnt as an associate of the picture (e.g. blark) or (d) an untrained nonword (e.g. domple). Novel object pictures (Finnish farm tools) were followed by an unrelated real word or trained or untrained nonwords. ERP analyses were carried out on mean and peak amplitudes between 300 and 450ms post word onset. There was no significant difference in the N400 reduction for pre-existing congruent words and trained nonwords linked to familiar or novel objects. This finding suggests that within this paradigm, the N400 indexes word-to-object mapping which can be rapidly established in adults. Email: d.copland@uq.edu.au EOG Correction Review and Program“EOG correction” is a method whereby portions of ocular voltage are subtracted from electroencephalogram (EEG) channels in order to reduce the artefact that such ocular voltages introduce to the EEG. There are a number of issues relating to EOG correction, such as the number of ocular contributions that need to be accounted for and in particular whether blinks and saccades need to be accounted for differentially, whether EOG propagation is frequency dependent, whether forward propagation of neural potentials is a concern to EOG correction, and how the various EOG correction techniques compare to one another. This presentation will provide a summary of these issues, and will further present an instantiation of the Revised Artifact-Aligned Average EOG correction method that is available to researchers at no cost. Email: rcroft@swin.edu.au Theta Power Reductions Under Cognitive Load in Amnestic Mild Cognitive ImpairmentAmnestic mild cognitive impairment (aMCI) is classified primarily via substantial episodic memory deficits in the absence of a dementia diagnosis. To investigate potential disruptions of memory-related brain function in this condition we compared QEEG power between 12 participants with aMCI and 12 matched healthy controls. EEG was acquired during performance of a modified Sternberg recognition task using study list lengths of 4 or 8 words (low and high memory load). While recognition accuracy of aMCI participants was lower than that of controls, this difference was not significant. Nevertheless the aMCI group demonstrated significantly lower theta power relative to the control group at frontal midline electrodes. Furthermore in the aMCI sample only, theta power was significantly lower under high versus low memory load. Given that theta oscillations are proposed to reflect not purely memory function but also more general processes such as cognitive control, the current data indicate that amnestic deficits in aMCI may reflect more generalised cognitive deficits. Moreover these outcomes provide novel neurophysiological evidence that such deficits are exacerbated under higher cognitive load. If replicated in larger samples such findings would have substantial implications for current concepts of amnestic MCI. Email: tarrant@psy.uq.edu.au Motor Plans Influence the Visual Processing of Observed ActionsThe perception and the execution of action appear to be linked by common neural mechanisms. Observed actions lead to increased activity in motor and premotor cortical areas and can interfere with the execution of opposite or incongruent actions. The “mirror” system has been suggested to mediate this link, directly matching observed actions onto equivalent motor representations in the motor system. While many studies have focussed on the influence of observed actions on the motor system, it is not known whether motor plans can similarly influence earlier visual processing associated with the perception of actions in a top-down manner. We tested this hypothesis specifically by examining visual evoked potentials (64-channel EEG) to images of hand gesture actions that were either congruent or incongruent with hand actions concurrently planned by participants in a Go-NoGo paradigm. The visual processing of observed actions was found to be significantly influenced by concurrent motor plans. Specifically, the N170 component of visual evoked potentials, known to be associated with the processing of biological stimuli, was significantly enhanced when observed actions were incongruent with concurrently planned actiona. Crucially, this effect was specific to the congruency of motor plans, and was not observed in a control condition involving similar stimulus incongruency but without motor planning. Our results provide further evidence for the association between the perception and execution of action, perhaps mediated by a mirror neuron system. Specifically, we have shown that motor plans or representations in the motor system can influence the visual processing of observed actions. Email: r.cunnington@uq.edu.au Ready….Set…. Switch: A. ERP Evidence for Activation and Inhibition Components of Task-Set ReconfigurationIn task-switching paradigms, switch trials show longer reaction time (RT) and more errors than repeat trials. This “switch cost” is reduced with increased time to prepare, suggesting a role for active preparation. The current study examined whether this preparation process involves both activation and inhibition-related components. 23 undergraduates participated in a cued-trials switching paradigm with 3 tasks. Both behavioural and event related potentials measures were recorded. Four cue types signaled the requirements of the next trial: repeat (ie., will repeat Task A), switch-to (ie., will switch to Task B), switch-away (ie., will not repeat Task A) and non-informative (ie., may repeat Task A or switch to Task B) cues. We tested Nicholson et al.’s (2006) hypothesis that the differential switch positivity (D-pos1) is associated with inhibition of a previously relevant task-set. There was no RT difference between switch-away and non-informative trials indicating no behavioural advantage of knowing that a task would not be repeated. However ERPs showed a large D-Pos1 component for both switch-to and switch-away trials but not for non-informative trials. This is compatible with an active inhibition component of task-set reconfiguration that does not necessarily affect behavioural outcomes. The implications for models of task-switching will be discussed. Email: Kasey.galloway@studentmail.newcastle.edu.au The Psychophysiology of Win and Loss Events During Electronic Machine Gambling: High Versus Low StakesAustralia has the dubious distinction of having the most number of electronic gaming machines (EGM; also known as poker-machines) per capita than any other country. Close to 300,000 Australians suffer from problem gambling, with the vast majority of gamblers in treatment reporting problems linked to EGMs. Although current psychological theories suggest that arousal mechanisms are implicated in the aetiology and perpetuation of gambling behaviours, the psychophysiological profiles of win- and loss-events during gambling on EGMs have not been systematically studied. The current study examined electrodermal and heart rate activity to wins and losses under high and low stake conditions in a gambling task. Participants were 20 university students who played an electronic gaming machine in an attempt to win movie vouchers. Wins produced significant heart rate and SCR elevations (compared to baseline) during the 10-second period following the event, whereas losses were associated with no changes in HR or SCR. As compared to low stakes, wins during the high stake condition produced larger increases in HR and SCR. The study has important clinical implications. Email: craigg@uow.edu.au The Effects of Acute Sleep Deprivation on a Cross-Modal Divided Attention Task: a Functional Neuroimaging StudySleepiness contributes to a large proportion of motor vehicle accidents worldwide. Driving is a complex task, which involves constant division of attention between different sensory modalities. This study examined the behavioural and neurofunctional effects of 27-hours sleep deprivation (SD) on performance of a cross-modal divided attention task. Twelve male professional drivers participated (M = 39.0 ± 8.1 years). Drivers were screened for sleep disorders, drug use, and other medical conditions contraindicating sleep deprivation. Drivers attended two functional magnetic resonance scans; after normal sleep, and following 27-hours SD. During each session, drivers completed a task that involved selective visual and auditory attention, and divided attention. A fixed effects analysis was performed on the functional data. After normal sleep, visual and auditory selective attention resulted in significant activations in primary sensory areas associated with these modalities (occipital and temporal cortices respectively), in addition to prefrontal and parietal areas associated with attention. In addition, the divided attention task activated the superior and inferior frontal gyri, anterior cingulate, and inferior parietal cortices. There was no effect of SD on performance. Following SD, the increased processing due to divided attention was further enhanced in anterior cingulated, caudate nucleus, and left superior frontal cortex (compared to normal sleep). These findings suggest that SD results in more processing in certain regions associated with divided attention processes, and further that additional brain regions are also activated. As no behavioural changes were observed, this suggests that these additional activations may act as compensatory mechanisms. Email: mjackson@swin.edu.au ERPs Dissociate Sequence Effects in Task SwitchingBehavioural investigations of task switching have revealed switch cost is eliminated on trials immediately following a no-go trial. Researchers investigating this effect claim that this no-go effect is not due to inhibition of a prepared task set, and that the effect is independent of preparation (Schuch & Koch, 2003; JEP:HPP, 29, 92-105). We examined these claims using event-related potentials. Participants (n=24) switched between letter and digit tasks randomly presented in blocks with go and no-go trials. Switch cost was significantly reduced in trials following no-go trials. Cue-locked waveforms showed no differences between trials preceded by go or no-go trials. Stimulus-locked waveforms of the no-go trials showed an increased N2/P3 complex. Response-locked waveforms showed differentiation between trials following no-go trials and those following go trials that began well before response-locked LRP onset. Cue-locked results were consistent with the proposal that the no-go effect is independent of preparation; however, stimulus-locked effects suggest that inhibition is occurring in the no-go trials, contrary to Schuch and Koch’s (2003) argument. The results of the response-locked waveforms suggest that rather than a prepared response being inhibited in no-go trials, it is more difficult to select any response following a no-go trial. Email: Sharna.Jamadar@newcastle.edu.au Cognitive Training for Children With ADHD: a Pilot Study Examining Behaviour, Task Performance and ERPsAttention-Deficit/Hyperactivity Disorder (ADHD) is characterised by symptoms of inattention and/or hyperactivity, with core deficits in response inhibition (RI) and working memory (WM). The present study examines the effectiveness of a computerized cognitive training program which aims to improve both RI and WM ability. Overt behaviour, Go-Nogo task performance and ERPs were examined before and after completion of the 5-week training program, with two conditions: the control, in which the training program remained at a constant easy difficulty level; and the experimental, in which the tasks increased in difficulty as performance improved. The design was randomised and double-blind in regard to group assignment. The results indicated that ADHD symptom frequency tended to decrease after training, with trends for improved accuracy and button-press RT on the Go-NoGo task, particularly in the experimental group. Several effects of training on ERP components were found, with a key effect indicating greater anteriorisation of the NoGo P3 in the experimental group. It is concluded that, although further research is required, this study supports the use of RI and WM training in normalising behaviour and underlying brain activity of children with ADHD. Email: sjohnsto@uow.edu.au Essential Ingredients: Optimizing Anticipatory Task-Set ReconfigurationAnticipatory task-set reconfiguration refers to the activation of task rules in anticipation of an impending change in task leading to a reduction in the behavioural cost of switching tasks. This process is associated with increased positivity within the cue-stimulus interval (CSI) for switch as compared to repeat trials (Karayanidis et al., 2003, Psychophys 40,329-348). Monsell and Mizon (2006, JEP:HPP,32,493-516; Nicholson et al., 2005, Psychophys, 42, 540-554) outlined a series of experimental conditions that increase the activation of task-set reconfiguration as measured by reduced behavioural switch cost. These include incentives to reward prepared performance, low probability of switch trials and, to a lesser degree, blocking CSI manipulation. In the present study, we examined the relative effectiveness of these manipulations against a common baseline condition. Switch probability produced the largest effect on behavioural switch cost, reduction in switch cost and switch positivity. Incentives increased overall task readiness as evidenced by faster RT and larger stimulus preceding negativity (SNP) but RT switch cost and switch positivity was affected only for fast responders only. Randomised CSI increased task readiness and reduced switch cost at the longest CSI. Results support strategic influence on activation of task-set reconfiguration and define conditions for optimizing preparation. Email: Frini.karayanidis@newcastle.edu.au The Effects of Serotonergic and Noradrenergic Antidepressants on the Temporal Course of Emotional Processing: an Event-Related Potential (ERP) StudySerotonergic (SSRI) and noradrenergic (NRI) antidepressant drugs have been shown to modulate biases in emotional processing. However, the effects of serotonergic and noradrenergic modulation on the temporal course (occurring in milliseconds) of emotional processing, and in particular, the rapid physiological changes associated with the different stages of emotional processing, are unknown. The present study assessed the effects of acute serotonergic (i.e. with citalopram) and noradrenergic (i.e. with reboxetine) augmentation on event related potential (ERP) measures associated with ‘structural encoding’ (N170) and emotion expression decoding (N250 and LPP) for positive (happy) and negative (sad) facial stimuli. The study employed a double blind, placebo- controlled cross- over design, in which 12 healthy male participants completed a facial expression recognition task tested under three acute conditions: a) placebo b) citalopram (20mg) and c) reboxetine (4mg). Results indicated that both citalopram and reboxetine had no effect on the N170 associated with structural encoding, potentiated the N250 associated with positive (happy) emotional facial expression decoding, whilst having no effects on later ERP measures of emotion expression decoding (LPP). These findings suggest that citalopram and reboxetine have selective effects on the temporal course of emotional processing, with evidence to suggest effects specifically on emotion expression decoding, but not structural encoding for positive emotional stimuli. Furthermore, the findings provide physiological evidence that antidepressants may shift bias in emotional processing away form negative and towards positive stimuli. Email: Rebecca.Kerestes@med.monash.edu.au Effects of Cognitive Processing Load on Cardiac and ERP Responses to Simple StimuliPrevious research has suggested that the complex phasic evoked cardiac response (ECR) produced by innocuous stimuli requiring cognitive processing may be described as the sum of two independent response components. An initial heart rate deceleration (ECR1), and a slightly later HR acceleration (ECR2), have been hypothesised to reflect stimulus registration and cognitive processing load, respectively. This study aimed to investigate the effects of processing load in the ECR and the event-related potential, in an attempt to link measures found important in the autonomic Orienting Reflex (OR) context to ERP components. We examined the effects of cognitive load within-subjects, using a long-ISI, autonomic OR-type paradigm. Subjects were presented with 30-35 80 dB, 1000 Hz tones with a variable ISI (7-9 s), and required to silently count, or allowed to ignore, the tone in each of two counterbalanced stimulus blocks. The ECR showed a significant effect of counting, allowing separation of the two ECR components by subtracting the no count from the count condition. The auditory ERP showed the expected obligatory processing effects in the N1, and substantial effects of cognitive load in the late positive complex (LPC). The results are discussed in the context of a sequential-processing model of the OR. Email: cal05@uow.edu.au Effects of Sex and Age on Prepulse Inhibition of the Startle ReflexThe effects of participant sex and age on blink startle and prepulse inhibition of blink startle were investigated in a sample of 732 participants aged 6 to 86 years. On pulse alone trials females had larger blink magnitude, probability, and amplitude and shorter onset latencies than males. Blink magnitude, probability and amplitude declined with increasing age. No sex effects emerged for prepulse inhibition. Prepulse inhibition of blink magnitude, probability and amplitude was smaller in children younger than 12 years and in adults older than 65 than in the remaining age groups. These results confirm some of the previous findings reported in smaller samples of age dependent changes in startle prepulse inhibition. Email: o.lipp@psy.uq.edu.au Autonomic Responses and Event-Related Potentials in an Indifferent Orienting Reflex ContextWe explored autonomic and central response patterning in a passive auditory habituation task. An alternating sequence of 16 tones (60/80 dB, 1500 Hz, 40 ms duration [15 ms rise/fall times], random ISIs [45 to 70 s]), was presented (order balanced between subjects; N = 18). There was no stimulus-related task. At each stimulus presentation, the skin conductance response (SCR), evoked cardiac response (ECR), and the single-trial ERP, were obtained. N1 and the Late Positive Complex (LPC) were estimated at each trial. Each response measure was analysed in a factorial design examining intensity and trials effects. SCR reflected stimulus intensity and showed significant decrement (habituation) over trials. The ECR, a simple heart rate deceleration, was unaffected by intensity or trials. N1, with a midline centro-parietal distribution, showed a frontal increase with stimulus intensity, but no decrement over trials. The LPC, with a fronto-central distribution, showed a main effect of
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