Computational EEG modelling of decision making under ambiguity reveals spatio-temporal dynamics of outcome evaluation.

Complex human cognition, such as decision-making under ambiguity, is reflected in dynamic spatio-temporal activity in the brain. Here, we combined event-related potentials with computational modelling of the time course of decision-making and outcome evaluation during the Iowa Gambling Task. Measures of choice probability generated using the Prospect Valence Learning Delta (PVL-Delta) model, in addition to objective trial outcomes (outcome magnitude and valence), were applied as regressors in a general linear model of the EEG signal. The resulting three-dimensional spatio-temporal characterization of task-related neural dynamics demonstrated that outcome valence, outcome magnitude, and PVL-Delta choice probability were expressed in distinctly separate event related potentials. Our findings showed that the P3 component was associated with an experience-based measure of outcome expectancy.

Event related potential (ERP) evidence for selective impairment of verbal recollection in abstinent recreational methylenedioxymethamphetamine ("Ecstasy")/polydrug users.

OBJECTIVES: Ecstasy is a recreational drug whose active ingredient, 3,4-methylenedioxymethamphetamine (MDMA), acts predominantly on the serotonergic system. Although MDMA is known to be neurotoxic in animals, the long-term effects of recreational Ecstasy use in humans remain controversial but one commonly reported consequence is mild cognitive impairment particularly affecting verbal episodic memory. Although event-related potentials (ERPs) have made significant contributions to our understanding of human memory processes, until now they have not been applied to study the long-term effects of Ecstasy. The aim of this study was to examine the effects of past Ecstasy use on recognition memory for both verbal and non-verbal stimuli using ERPs. METHODS: We compared the ERPs of 15 Ecstasy/polydrug users with those of 14 cannabis users and 13 non-illicit drug users as controls. RESULTS: Despite equivalent memory performance, Ecstasy/polydrug users showed an attenuated late positivity over left parietal scalp sites, a component associated with the specific memory process of recollection. CONCLUSIONS: [corrected] This effect was only found in the word recognition task which is consistent with evidence that left hemisphere cognitive functions are disproportionately affected by Ecstasy, probably because the serotonergic system is laterally asymmetrical. Experimentally, decreasing central serotonergic activity through acute tryptophan depletion also selectively impairs recollection, and this too suggests the importance of the serotonergic system. Overall, our results suggest that Ecstasy users, who also use a wide range of other drugs, show a durable abnormality in a specific ERP component thought to be associated with recollection.

Electrophysiological correlates of anxious rumination.

EEG coherence and EEG power response were recorded as 63 participants engaged in one of three experimental conditions: 'personal rumination', 'nominal rumination', and 'baseline counting'. The rumination conditions were separated by a neutral (counting) task to eliminate neural carry-over effects. For personal rumination, participants spent 2 min ruminating about something in their life about which they were in two minds (i.e., in a state of personal conflict). For nominal rumination, they were presented with a conflict scenario (concerning buying a car) and instructed to ruminate about that for 2 min. The baseline counting task simply involved counting forwards from 1 at a speed comfortable to the individual. Participants completed various questionnaires to measure mood and also traits of personality (including trait anxiety). EEG data were analysed in the following wavebands: 4-6 Hz, 6-8 Hz, 8-10 Hz, 10-12 Hz, 12-20 Hz and 20-30 Hz. Results revealed that the scalp-wide EEG theta (4-6 Hz and 6-8 Hz) coherence associated with personal rumination was significantly greater than that associated with nominal rumination and baseline counting. Similarly, the scalp-wide 6-8 Hz and parietal-occipital 4-6 Hz power associated with personal rumination were significantly greater than power associated with the nominal rumination and power for baseline counting. For alpha, the 10-12 Hz scalp-wide EEG coherence associated with personal rumination was significantly greater than that associated with baseline counting. Otherwise, the scalp-wide 10-12 Hz power related to both nominal rumination and personal rumination were significantly greater than in response to baseline counting. For 20-30 Hz scalp-wide EEG power, data in response to the nominal rumination condition were significantly increased compared to data associated with the baseline counting condition. In terms of questionnaire data, tense arousal, anger/frustration, hedonic tone and energetic arousal were all influenced by rumination. This was largely in line with expectation. Also, mood state was influenced by neuroticism and state anxiety. Our EEG results are consistent with Gray and McNaughton's [Gray, J.A., McNaughton, N., 2000. The neuropsychology of Anxiety: An Anquiry into the Functions of the Septo-Hippocampal System. 2nd ed. Oxford University Press, Oxford.] account of recursive processing between the septo-hippocampal system and neocortex during goal-conflict resolution inherent in rumination. Evidence of posterior cingulate involvement in this processing was also discussed. Recommendations for future research, aimed at further evaluating the role of the SHS and the posterior cingulated, were outlined. Effects found in alpha were linked to increased vigilance whilst effects in beta were linked to cognitive and emotional aspects of the task. We conclude that these data provide new information of the neural processes associated with the psychological state of anxious rumination and, thus, hold implications for understanding normal and pathological anxiety.

Prediction of subjective states from psychophysiology: a multivariate approach.

Biocybernetic systems utilise real-time changes in psychophysiology in order to adapt aspects of computer control and functionality, e.g. adaptive automation. This approach to system design is based upon an assumption that psychophysiological variations represent implicit fluctuations in the subjective state of the operator, e.g. mood, motivation, cognitions. A study was performed to investigate the convergent validity between psychophysiological measurement and changes in the subjective status of the individual. Thirty-five participants performed a demanding version of the Multi-Attribute Task Battery (MATB) over four consecutive 20-min blocks. A range of psychophysiological data were collected (EEG, ECG, skin conductance level (SCL), EOG, respiratory rate) and correlated with changes in subjective state as measured by the Dundee Stress State Questionnaire (DSSQ). MATB performance was stable across time-on-task; psychophysiological activity exhibited expected changes due to sustained performance. The DSSQ was analysed in terms of three subjective meta-factors: Task Engagement, Distress and Worry. Multiple regression analyses revealed that psychophysiology predicted a substantial proportion of the variance for both Task Engagement and Distress but not for the Worry meta-factor. The consequences for the development of biocybernetic systems are discussed.

The influence of task demand and learning on the psychophysiological response.

The level of expertise of an operator may significantly influence his/her psychophysiological response to high task demand. A naive individual may invest considerable mental effort during performance of a difficult task and psychophysiological reactivity will be high compared to the psychophysiological response of a highly skilled operator. A study on multitasking performance was conducted to investigate the interaction between learning and task demand on psychophysiological reactivity. Thirty naive participants performed high and low demand versions of the Multi-attribute Task Battery (MATB) over a learning period of 64 min. High and low task demand setting were preset via a pilot study. Psychophysiological variables were collected from four channels of EEG (Cz, P3, P4, Pz), ECG, EOG and respiration rate to measure the impact of task demand and learning. Several variables were sensitive to the task demand manipulation but not time-on-task, e.g., heart rate, Theta activity at parietal sites. The sensitivity of certain variables to high demand was compromised by skill acquisition, e.g., respiration rate, suppression of alpha activity. A sustained learning effect was observed during the high demand condition only; multiple regression analyses revealed that specific psychophysiological variables predicted learning at different stages on the learning curve. The implications for the sensitivity of psychophysiological variables are discussed.