CENTRIFUGAL INPUTS ENHANCE RESPONSES OF RETINAL GANGLION-CELLS IN THEJAPANESE-QUAIL WITHOUT CHANGING THEIR SPATIAL CODING PROPERTIES

Centrifugal fibers originating in the midbrain innervate the avian ret ina. Stimulation of the centrifugal fibers enhances the responses of g anglion cells in the retinas of both chick and pigeon. The enhanced re sponses have been attributed to disinhibition, a reduction of the inhi bitory surround component of the receptive fields of retinal ganglion cells. We found that stimulation of the centrifugal fibers in Japanese quail enhances the responses of retinal ganglion cells to drifting si ne-wave gratings over a wide range of spatial frequencies. Our results do not support the idea that centrifugal inputs selectively influence receptive field surrounds. We also found that centrifugal inputs chan ged the temporal response properties of retinal ganglion cells by enha ncing their responses to sine-wave gratings drifting across the retina at higher temporal frequencies (> 5 Hz). The result shows that centri fugal inputs from the midbrain can enhance responses of retinal gangli on cells without affecting the center-surround organization of their r eceptive fields. The centrifugal modulation of retinal responses may h ave a role in shifting visual attention.