Author:

Keywords:

Social Sciences, Science & Technology, Life Sciences & Biomedicine, Psychology, Biological, Behavioral Sciences, Psychology, Psychology, Experimental, Fixation-related potentials (FRPs), EEG, P300, Visual search, Eye movements, Target probability, EVENT-RELATED POTENTIALS, INDEPENDENT COMPONENT ANALYSIS, STIMULUS SEQUENCE, P300 COMPONENT, SURPRISE, TASK, P3A, ARTIFACTS, RELEVANCE, Adult, Attention, Cerebral Cortex, Event-Related Potentials, P300, Evoked Potentials, Female, Fixation, Ocular, Humans, Male, Probability, Visual Perception, Young Adult, 1109 Neurosciences, 1701 Psychology, 1702 Cognitive Sciences, Experimental Psychology, 3209 Neurosciences, 5202 Biological psychology, 5204 Cognitive and computational psychology

Abstract:

This study investigated the influence of target probability on the neural response to target detection in free viewing visual search. Participants were asked to indicate the number of targets (one or two) among distractors in a visual search task while EEG and eye movements were co-registered. Target probability was manipulated by varying the set size of the displays between 10, 22, and 30 items. Fixation-related potentials time-locked to first target fixations revealed a pronounced P300 at the centro-parietal cortex with larger amplitudes for set sizes 22 and 30 than for set size 10. With increasing set size, more distractor fixations preceded the detection of the target, resulting in a decreased target probability and, consequently, a larger P300. For distractors, no increase of P300 amplitude with set size was observed. The findings suggest that set size specifically affects target but not distractor processing in overt serial visual search.