Change detection in the surrounding world : evidence from visual and somatosensory brain responses

Abstract

Change detection is crucial for our daily lives. There are two research traditions for change detection: (1) change detection that investigates changes between two successively presented pictures with a time interval inserted, for which attention is considered necessary; and (2) deviance detection, which refers to the detection of changes that violate certain regularities in serially presented stimuli and can be conducted in an unattended condition. In Study I, I reviewed contradictory results from studies that applied attentive visual search and change detection tasks to study emotional bias in the perception of facial expressions. Three possible contributing factors that have significant impacts on the contradictory results were proposed, namely, differences in stimuli, differences in experimental settings, and differences in underlying cognitive processes. In Studies II and III, using magnetoencephalography, I investigated deviance detection in regularity formed by serially presented facial expressions and the location of electrical pulses. In Study II, I investigated to what extent the automatic encoding and change detection of paracentrally presented facial expressions is altered in dysphoria. The brain responses demonstrated that with both happy and sad faces, changes could be detected automatically. However, dysphoric individuals exhibited a negative perceptual bias toward sad faces in addition to a general deficit in the pre-attentive deviance detection processing. In Study III, a novel oddball task was introduced to investigate brain responses to unpredictable and predictable rare somatosensory events. The results showed that rare stimuli elicited two main brain activity components in the primary and secondary somatosensory areas contralateral to the stimulation. However, the results linked only the earlier component, at 30‒100 ms after stimulus onset, to the prediction error signals. The results of Study III also highlighted the need to disentangle the effects of stimulus rareness and predictability in future studies. Overall, this dissertation brings together two relatively separate but related research domains of change detection. In addition to reviewing evidence of change detection, this dissertation provides empirical evidence of deviance detection in both the visual and somatosensory modalities and raises suggestions for future research on both types of change detection.