The role of selective attention during visual search using random dot motion stimuli.

Abstract

Finding objects among distractors is an essential everyday skill, which is often tested with visual search tasks using static items in the display. Although these kinds of displays are ideal for studying search behavior, the neural encoding of the visual stimuli can occur rapidly, which limits the analysis that can be done on the accumulation of evidence. Searching for a target among multiple random dot motion (RDM) stimuli should allow us to study the effect of attention on the accumulation of information during visual search. We trained an animal to make a saccade to a RDM stimulus with motion in a particular direction (the target). The animal began the task by fixating a central square. After a short delay, it changed to a dotted hollow square and one, two or four RDM stimuli appeared equally spaced in the periphery for 700 ms. The animal was rewarded for looking at the target, if present, or for maintaining fixation if the target was absent from the display. In the spread attention condition, all the dots in the RDM stimuli were the same color. In the focused attention condition, the color of the fixation square and the dotted hollow square matched the color of the dots in one RDM stimulus, which was a 100% valid cue. We varied the coherence of the RDM stimuli for each condition from 65 to 100% (100 ms limited lifetime). At the lower coherences, there were strong effects of set size and attention condition on both performance and reaction time. Our data show that using a RDM visual search task allows us to clearly illustrate the role of attention in the accumulation of perceptual evidence, which increases response accuracy and shortens reaction time. Meeting abstract presented at VSS 2015