We propose a neural model for object-oriented attention in which various visual stimuli (shapes, colors, letters, etc.) are represented by competing, mutually inhibitory, cell assemblies. The model's response to a sequence of cue and target stimuli mimics the neural responses in infero temporal (IT) visual cortex of monkeys performing a visual search task: enhanced response during the display of the stimulus, which decays but remains above a spontaneous rate after the cue disappears. When, subsequently a display consisting of the target and several distracters is presented, the activity of all stimulus-driven cells is initially enhanced. After a short period of time, however, the activity of the cell assembly representing the cue stimulus is enhanced while the activity of the distracters decays because of mutual competition and a small top-down 'expectational' input. The model fits the measured delayed activity in IT-cortex, recently reported by Chelazzi, Miller, Duncan, and Desimone, and we suggest that such a process, which is largely independent of the number of distracters, may be used by the visual system for selecting an expected target (appearing at an uncertain location) among distracters.
ASJC Scopus subject areas
- Cognitive Neuroscience