Abstract
Numerous studies have shown that we are capable of tracking 4 or 5 moving objects simultaneously. In this study we examined an electrophysiological measure in humans that appears to reflect the tracking of multiple objects “online” during a trial. Subjects were shown a bilateral display of multiple moving objects and were asked to track the objects in a single hemifield for an occasional brief flicker of one of the tracked objects. We time-locked the ERPs to the onset of the moving objects and recorded throughout the trial. Approximately 400ms following the onset of the movement, we observe a sustained negative wave at electrode sites that were contralateral with respect to the hemifield the subject was tracking. This wave persisted throughout the entire trial and its amplitude increased as a function of the number of items the subject was tracking on a given trial (1, 2, or 4 items). Together, these results suggest that this activity reflects a neural mechanism for tracking multiple objects.