Abstract
The superior colliculus (SC) plays an important role in the control of visual spatial attention, in particular in situations where such control involves saccades. We wondered if it also plays a role in the control of object-based attention, motivated by the fact that saccades are often directed not simply to locations in space but rather to parts of extended objects. A rhesus monkey was trained to fixate a spot of light and make a saccade to a peripheral cue. On each trial, an extended object was presented along with two stimuli indicating potential saccade goals. The correct saccade goal was randomly selected from the two stimuli and was cued by a subtle spatial extension of its length. In the connected condition, the potential saccade goals were contiguous with the extended object. In the disconnected condition, they were presented at the same spatial locations but were separated from the extended object by a short distance. We recorded from SC neurons that had response fields (RFs) that overlapped the extended object yet were spatially remote from the saccade goals. Thus, in the connected condition, the saccade goal and RF stimulus were part of the same extended object, whereas, in the disconnected condition, they were not. Otherwise, the saccade goals, the saccades that were made, and the RF stimuli were the same. Nevertheless, we found that, around the time of saccade execution, SC activity was enhanced in the connected condition relative to the disconnected condition. This suggests that, during a saccade to an extended object, there is an enhanced representation of that object at the level of the SC. The results, therefore, suggest a potential role for the SC in object- as well as space-based attentional control, at least when the object to be attended is the target of an impending saccade.