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Abstract:
Abstract: How does discriminative processing in vision vary
between task-relevant and task-irrelevant information? To address
this question, subjects viewed stimuli presented at fixation,
either a letter (an A or an H, which was rapidly masked) or a
square-wave grating. In the "task-relevant" condition, a letter
discrimination was required on non-grating trials, while in the
"task-irrelevant" condition, all stimuli were passively viewed.
Event-related potentials (ERPs) were recorded as a function of
stimulus type and task condition. Comparing ERPs to the grating
stimuli as a function of task condition revealed the nature of the
visual processing events that are associated with discrimination
for task-relevancy, when the relevancy discrimination is based on
stimulus features. In turn, comparing the letter stimuli between
task conditions revealed the processing events that arise for
stimuli that are selected as task-relevant, and that require
further feature-based discrimination. These ERP results have direct
implications for the suggestion that the amplitude of the occipital
N1 ERP component is enhanced for stimuli requiring discrimination
(e.g., Luck, 1995).
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