Michael S. Goodman ’74 Memorial Seminar Series. Perception & Action Seminar Series. Speaker: Robert Desimone, MIT. Title: Neural mechanisms of feature and spatial attention. Abstract: Normal vision typically involves a close association between feature attention, spatial attention, and eye movements. For example, during search for a target in a cluttered scene, the search is guided by attention to target features and objects are sampled by saccadic eye movements in the theta frequency range. Behavior in such tasks is thought to be mediated in part by an interaction between the ventral pre-arcuate cortex (VPA) in ventral PFC and the frontal eye fields (FEF). Feedback from VPA appears to enhance processing of stimuli sharing target features, and feedback from FEF enhances the processing of stimuli that are the target of eye movements. By contrast, covert spatial attention is commonly thought to be an alternative mode of attention, which also depends on FEF but is thought to occur independently of eye movements. However, our recent evidence suggests that even in covert attention paradigms, attention shifts rhythmically in conjunction with microsaccades, which also occur in the theta range. Visual responses are enhanced only during microsaccade towards a target. Thus, regardless of the behavioral context, feature attention, dependent on feedback from VPA, appears to act globally on visual representations, whereas spatial attention, dependent on feedback from FEF, acts locally on stimuli that are the target of eye movements.