ARE THE SAME ATTENTIONAL MECHANISMS USED TO DETECT VISUAL-SEARCH TARGETS DEFINED BY COLOR, ORIENTATION, AND MOTION

Motion information tends to be segregated from color and form informat ion in the visual system, both perceptually and neuroanatomically, and it is therefore possible that different mechanisms of attention are u sed to select targets defined by these different feature types during visual search. To test this hypothesis, we recorded the N2pc component of the event-related potential waveform during visual search tasks wi th color, orientation, and motion targets. The N2pc component has prev iously been shown to reflect a specific attentional mechanism that is present for color and form targets, and we sought to determine whether this component would also be present for motion targets. The N2pc com ponent was indeed observed for motion targets as well as color and ori entation targets, consistent with the use of a common attentional mech anism across feature types. In addition, we found that motion singleto ns (i.e., individual items that moved in the opposite direction from t he other items in the array) elicited an N2pc component even when they were task-irrelevant, indicating that motion discontinuities map prod uce an automatic orienting of attention.