Time course of attention reveals different mechanisms for spatial and feature-based attention in area V4.
Attention can facilitate visual processing, emphasizing specific locations and highlighting stimuli containing specific features. To dissociate the mechanisms of spatial and feature-based attention, we compared the time course of visually evoked responses under different attention conditions. We recorded from single neurons in area V4 during a delayed match-to-sample task that controlled both spatial and feature-based attention. Neuronal responses increased when spatial attention was directed toward the receptive field and were modulated by the identity of the target of feature-based attention. Modulation by spatial attention was weaker during the early portion of the visual response and stronger during the later portion of the response. In contrast, modulation by feature-based attention was relatively constant throughout the response. It appears that stimulus onset transients disrupt spatial attention, but not feature attention. We conclude that spatial attention reflects a combination of stimulus-driven and goal-driven processes, while feature-based attention is purely goal driven.
Hayden
Benjamin Y
BY
Department of Molecular and Cell Biology, Berkeley, California 94720, USA.
Gallant
Jack L
JL
D000818:Animals; D001288:Attention / Q000502:physiology*; D004567:Electrodes, Implanted; D005074:Evoked Potentials, Visual / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D005403:Fixation, Ocular; D005556:Form Perception / Q000502:physiology*; D008253:Macaca mulatta; D009474:Neurons / Q000502:physiology; D010775:Photic Stimulation; D013028:Space Perception / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*