A dynamic model of how feature cues guide spatial attention.

We will describe a computational model of attention which explains the guidance of spatial attention by feedback within a distributed network. We hypothesize that feedback within the ventral pathway transfers the target template from prefrontal areas into intermediate areas like V4. The oculomotor circuit consisting of FEF, LIP and superior colliculus picks up this distributed activity and provides a continuous spatial reentry signal from premotor cells. In order to test this hypothesis, we simulate two experiments that require a response given a color cue. The first experiment indicates a parallel feature-based enhancement prior to any spatial selection. If two targets are behaviorally relevant, as in the second experiment, experimental findings indicate that subjects split their attention between two locations containing the searched feature. Our simulation results suggest that the split in attention between two foci is a transient effect occurring during competition. We predict that the time after cue presentation determines the state of this competition and ultimately the distribution of attention at different locations. In addition we provide simulation results to explain how reentrant processing through the oculomotor circuit might lead to variations of the time for target detection in visual search.