Deficits of masticatory movements caused by lesions in the orofacial somatosensory cortex of the awake cat.

The purpose of this study was to determine the role of somatosensory cortex (SI) in the control of orofacial movements during eating. We identified perioral and tongue projection regions of the cat SI and destroyed cells in one region by injecting kainic acid. The effects on orofacial behavior were then studied over a period of 4-6 weeks. Cats with unilateral lesions in the perioral region (PL-cats) dropped food from the contralateral side of the mouth in the early phase. Failure in erection of the contralateral whisker hairs during masticatory movements and delay of the masticatory start were observed throughout the experimental period. Furthermore, in the late phase, PL-cats showed prolongations of the masticatory and food intake periods, which were accompanied by the increase in the number of swallows and chewing cycles. Cats with unilateral lesions in the tongue region (TL-cats) showed the prolongation of the masticatory period in the early phase, which was accompanied by the increase in the number of swallows and chewing cycles. TL-cats did not show the prolongation of the food intake period and failure in erection of the contralateral whisker hairs. In both PL- and TL-cats, masticatory and swallowing rhythms were normal.