An ERP investigation of response-related processes

Several ERP correlates of response-monitoring have been investigated over the past two decades, with a number of competing theories emerging. Models of early negative components focus on explanations involving a comparative process between error and correct responses or a reinforcement-learning process. These theories are representative of either a specific error-processing or a generic response-monitoring system. These models provide some structure to explain experimental outcomes, but fail to account for much evidence, particularly in terms of individual differences in goal-directed behaviour, response awareness and task-specific factors that may impact the overall evaluation of action and intention. Whereas some research evidence has indicated a clear and functional separation of early and later response-related components, other researchers have found associations where both early and later components are impacted by prevailing experimental conditions. Thus the overarching aim of this thesis was to investigate the impact of task difficulty, conscientiousness, task and response salience, response awareness and task-specific factors on both early and late, error and correct response-related ERP components. Experiment 1 focused on investigating task demands, response awareness and conscientiousness in terms of ERN/Ne, CRN, early and late Pe and corresponding Pc mean amplitudes, in a standard arrowhead two-choice flanker task. Overall errors were found to elicit larger mean amplitude than correct responses. No effects of response awareness were evident at any stage of the response evaluation process, however as this outcome was based on small sample sizes interpretation was approached cautiously. Conscientiousness was found to differentiate component amplitudes in terms of task difficulty, particularly for error-related components. Overall, results suggest that individual differences in terms of underlying personality traits may play a role in the evaluation of errors. Experiment 2 was designed to consider task difficulty in terms of overall response-monitoring using a four-choice flanker task. Response awareness and conscientiousness were also investigated. Again, analysis of early error and correct related components revealed significant amplitude differences. While early components also showed effects of response awareness this was based on very small sample sizes and as such did not provide a basis for a definitive interpretation. Similar to the outcomes of Experiment 1, differentiation of component amplitudes was apparent in terms of conscientiousness and task difficulty; however, in this instance this was only associated with correct response-related components. Experiment 3 aimed to examine the impact of task salience, conscientiousness and response awareness on response-related ERP components in a more complex language based task. Since ability to decode non-words was fundamental to the completion of the task, decoding ability was also included in the overall design and analyses. The initial analysis of this data including decoding ability and task salience revealed no significant differences in ERN/Ne and CRN mean amplitude indicating that response-related components may be impacted by task difficulty or stimulus discriminability. However, when further analyses were completed including conscientiousness, response awareness, and left and right coronal measures a differing picture began to emerge. Early negativities were found to be impacted by conscientiousness suggesting individual differences in goal directed behaviour should be considered in overall explanations of response- and error-monitoring processes. Clear coronal differences in late components indicated differential hemispheric processing in response evaluation. Since stimulus evaluation processes were also evidenced in differences in hemispheric activity, this outcome points to an explanation involving the specific nature of the phonological decoding task. Taken together, the findings of this series of experiments suggest that task-specific factors including task difficulty play a role in overall response evaluation processes, but that this also takes place within the context of individual personality differences. Furthermore, the evidence suggests that all response-related ERP components, early and late, error and correct, may combine to offer a fuller explanation of response-monitoring.