Abstract
Attending to a visual stimulus feature modulates the perception of that feature. Here, we used moving stimuli to investigate whether maintaining the representation of a visual feature in working memory (WM) produces a similar effect, and whether such effect interacts with the effect of feature-based attention (FBA). Seven subjects identified the direction of a brief pulse of coherent motion occurring in a 0% coherence random dot pattern (RDP). Concurrently, they performed a second task consisting of either a) attending to four sequentially presented moving RDPs and detecting whether they changed direction (Experiment 1), or b) remembering the direction of a moving RDP (sample) and, after a delay, determining how many of four sequentially presented RDPs (tests) matched the sample's direction (Experiments 2&3). In Experiment 1, the pulse co-occurred with one test, while subjects attended to it. In Experiment 2, the pulse occurred during an inter-test interval, while subjects remembered the sample. In Experiment 3, the pulse co-occurred with one of the tests, while subjects remembered the sample and attended to the test. Pulse identification performance was significantly higher when the pulse direction was the same as the concurrently attended RDP (FBA, Experiment 1) or the remembered sample (WM, Experiment 2), than when it was opposite. In Experiment 3, performance was highest when both the remembered sample and the attended test directions (WM+FBA) were the same as the pulse direction, intermediate when one was the same and the other opposite, and lowest when both were opposite. When subjects performed the pulse identification task but ignored the sample and tests, performance was unaffected by the sample and test directions, demonstrating that mere exposure to these stimuli did not influence pulse identification. Our results show that WM and FBA can individually and simultaneously modulate the perception of motion direction in human subjects.