Abstract
Locating target items among multiple distractors can be facilitated as one becomes familiar with the visual scene containing such items. As a step to investigate the neural mechanisms by which information about visual scenes can be acquired and used to locate targets efficiently, we trained monkeys to produce hand movements according to the locations of targets among multiple distractors. Targets and distractors were selected from a set of 9 different stimuli (3 different shapes in 3 different colors). A visual scene was defined by the distribution of these 9 different stimuli in the display. The animal was trained to move a feedback cursor to a series of targets by making hand movements on a touch screen. The first target in each trial was presented by itself, whereas distractors were present for the remaining targets. The identity of the next target item was indicated to the animal by presenting a sample in the current target location. The sample was made 50% larger than the target to distinguish it from other stimuli, and the interval between the acquisition of a given target and the onset of the sample was always 250 ms. In two separate experiments, we tested whether familiarity of visual scene influenced the search performance. Familiarity of a visual scene was manipulated by repeatedly presenting a particular scene chosen randomly each day, and performance was measured by the time taken from sample onset to target acquisition. In the first experiment, the location of each target was randomly determined, and performance improved as the visual scene became familiar to the animal. In the second experiment, target location followed a particular order in a majority of trials, and performance was better for familiar scenes even when the sequence of target locations was learned. As in previous human studies, these results suggest that knowledge of a visual scene can facilitate spatial orienting during search tasks in non-human primates.
Supported by a grant from James S. McDonnell Foundation and the NIH grants R01-MH59216 and P30-EY01319.