The purpose of the project is to study the effects of head and body tilt on the orientation specificity, orientation range, and other receptive field characteristics of single visual neurones of the geniculate body and primary visual cortex of cats. Efforts are continuing to quantitatively define the orientation specificity and range of simple field and complex field neurones of visual cortex as a function of the angle of a stimulus slit. The effects of tilt on single cells of the geniculate and visual cortex are recorded in acute preparations. The effects of acute and chronic interruption of the vestibular afferent information to the visual cortex on receptive field orientation will be studied.