Widespread distribution of visual responsiveness in frontal, prefrontal, and prelimbic cortical areas of the cat: an electrophysiologic investigation.

By using multiple-unit recording techniques, we explored the visual responsiveness of regions of cortex in and around the area described by others as the cat's "frontal eye fields" (Schlag J, Schlag-Rey M [1970] Brain Res 22:1-13; Guitton D, Mandl G [1978] Brain Res 149:295-312; Pigarev IN [1984] Neirofiziologiia 16:761-766). Our exploration included most of the cat's motor areas (subdivisions of areas 4 and 6) as well as prefrontal and prelimbic regions. Visual responses were routinely obtained from portions of each of the areas we explored, including prefrontal and prelimbic cortex. The qualitative characteristics of visual responses appeared to vary with cytoarchitectonic area. With few exceptions, receptive fields in these areas were large (most exceeding 2,500 deg2) and included the area centralis. Such large fields and inclusion of central vision at nearly all sites precluded retinotopic organization and prevented delineating distinct visual field representations. The most reliable and robust visual activity was observed on the ventral bank of the cruciate sulcus in area 6aalpha. The regions reported to correspond to the "frontal eye fields" did not exhibit any unique visual properties that distinguished them from surrounding areas. The widespread distribution of visually driven activity we observed is consistent with the known pattern of both cortical and subcortical inputs to this broad region of cortex. The observation of visually responsive activity across broad regions of cortex that is nominally motor is consistent with recent studies involving awake animals.