Time Course of Attention Reveals Different Mechanisms for Spatial and Feature-Based Attention in Area V4

• Published in: Neuron (Cambridge, Mass.) Mass.), 2005-09, Vol.47 (5), p.637-643
• Main Authors: Hayden, Benjamin Y., Gallant, Jack L.
• Format: Article
• Language: English
• Subjects: Animals; Attention - physiology; Brain; Electrodes, Implanted; Evoked Potentials, Visual - physiology; Excitatory Postsynaptic Potentials - physiology; Fixation, Ocular; Form Perception - physiology; Macaca mulatta; Neurons; Neurons - physiology; Photic Stimulation; Space Perception - physiology; Visual Cortex - cytology; Visual Cortex - physiology; Visual task performance
• ISSN: 0896-6273; 1097-4199
• DOI: 10.1016/j.neuron.2005.07.020

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.