Visual responses of area 18 neurons in awake, behaving monkey

The mechanisms underlying effects of ionizing radiation on visual-motor tasks in combat are not understood but definitely involve some disruption of visual perception. The degree of involvement is not known and must be studied and quantified in animal models. It is possible to identify those parts of the central nervous system necessary for visual perception. Once these areas have been identified, their sensitivity to irradiation can be studied more precisely. Visual responses of area 18 neurons were studied in the awake, behaving monkey. Cells were divided into six different classes on the basis of their stimulus preferences and spatial characteristics. Orientation cells were sensitive to the orientation of elongated stimuli. Color cells had nonoriented receptive fields with spatially coextensive opponent color inputs. Direction cells preferred moving stimuli, giving the greatest response to movement in some direction and no response or inhibition to movement in the opposite direction. Spot cells preferred a properly positioned small spot of light and responded equally well to all directions of stimulus movement. Border cells responded best to a stimulus that filled an excitatory region without encroaching on a powerful suppressive flank. Lightinhibited cells had high maintained spontaneous activity that was reduced or abolished by light.