Behavioral/Systems/Cognitive Suppressive Surrounds of Receptive Fields In Monkey Frontal Eye Field

Acritical step indetermininghowaneuron contributes to visual processing is determining its visual receptive field (RF).While recording fromneurons in frontal eye field (FEF) of awakemonkeys (Macacamulatta), weprobed the visual fieldwith small spots of light and found excitatory RFs that decreased in strength fromRF center to periphery. However, presenting stimuli with different diameters centered on the RF revealed suppressive surrounds that overlapped the previously determined excitatory RF and reduced responses by 84%, on average. Consequently, in that overlap area, stimulation produced excitation or suppression, depending on the stimulus. Strong stimu-lation of the RF periphery with annular stimuli allowed us to quantify this effect. A modified difference of Gaussians model that inde-pendently varied center and surround activation accounted for the nonlinear activity in the overlap area. Our results suggest that (1) the suppressive surrounds found in FEF are fundamentally the same as those in V1 except for the size and strength of excitatory and suppressive mechanisms, (2) methodically assaying suppressive surrounds in FEF is essential for correctly interpreting responses to large and/or peripheral stimuli and therefore understanding the effects of stimulus context, and (3) regulating the relative strength of the surround clearly changes neuronal responses and may therefore play a significant part in the neuronal changes resulting from visual attention and stimulus salience