The costs and benefits of emotional processing : behavioral performance and electrocortical dynamics

Abstract

A common perspective in contemporary emotion research states that the human brain processes emotionally arousing information in a near-optimal manner. This view has been derived from brain imaging work showing that viewing (or hearing) of emotionally charged stimuli enhances cortical responses at various stages of processing. However, empirical findings are less conclusive as to how affective stimulus perception translates into behavioral responses, especially when mental operations are carried out on the stimulus. The present thesis centers on the questions whether and when task performance is facilitated or impaired by emotional content of a stimulus. Behavioral and electrophysiological data of four experimental series are reported and discussed capitalizing on emotion-performance interactions in different perceptual and cognitive tasks. Aversive picture content was found to delay visual discrimination of natural scenes. Conversely, pleasant content accelerated categorization responses, especially when pictures were judged as mildly and not highly arousing. The behavioral pattern was mirrored by event-related brain potential measures (late positive potential latencies) indicative of cognitive processing time. Early electrocortical activation patterns pointed to the operation of three independent mechanisms underlying the response modulation: i) early sensitivity to appetitive features (between 90 - 130 ms), ii) selection of arousing events (200 - 250 ms), and, iii) attending to threat (300 - 400 ms). Detrimental effects of stimulus emotional content were found for subsequent processing of neutral information. Arousing pleasant and unpleasant pictures prolonged lexical decision times to neutral word/pseudowords irrespective of stimulus-onset asynchrony (80 ms, 200 ms, 440 ms) and salient semantic category differences (e.g., erotica versus mutilation pictures). On an electrocortical level, interference was reflected in reduced N1 (204 - 264 ms) and late positivity (LP, 404 - 704 ms) responses. Regional source modeling indicated that reduction effects originated from inhibited cortical activity in posterior areas of the left inferior temporal cortex associated with orthographic processing. Modeling of later reduction effects argued for interference in distributed semantic networks. Sustained interference with subsequent processing was also demonstrated for emotional words and pictures preceding word targets during Rapid Serial Visual Presentation. Finally, using a McGurk paradigm, facial and vocal expressions of emotion (pleasant and unpleasant) were associated with enhanced probability of audiovisual fusion. A hierarchical model is delineated, attempting to account for the outlined results. Task performance is predicted based on three dimensions: i) Connections of the target stimulus to an emotion network, ii) the assessment of speed versus accuracy measures, ii) the degree of emotional arousal.