Abstract
An emerging view of the attentional system is that feedback signals impinge on sensory processing areas so as to enhance attended stimuli at the expense of unattended stimuli. An important goal is to understand the nature of the circuitry that transforms these feedback signals into improved sensory processing. One model of this circuitry, the normalization model of attention, posits that the brain has co-opted gain-control circuits that may originally have evolved to adapt sensory processing to changes in the strength of sensory input. According to this proposal, attentional feedback signals to the visual system scale the inputs to normalization circuits in primary and extrastriate visual cortices. Recently Heeger and Reynolds proposed an extension to the normalization model of attention that incorporates a narrow excitatory field and a broader inhibitory field. This model makes two predictions about attentional modulation when a stimulus in a neuron's classical receptive field is paired with a second stimulus in the suppressive surround. Directing attention to the stimulus in the center should diminish surround suppression and directing attention to the surround stimulus should increase surround suppression. We tested this in macaque area V4 and find clear support for both predictions. These findings demonstrate that attention modulates the neural mechanisms that give rise to center-surround interactions, and provide support for the normalization model of attention.
Funding provided by NEI grant 1R01EY016161.