Function of the orofacial SI during mastication in awake cats: changes in masticatory movements and activities of mastication-related neurons in motor cortices following a lesion in the orofacial SI in awake cats

Receptive fields (RF) of well isolated single neurons. were studied in the orofacial somatosensory cortex (SI) of cats. Facial and intraoral neurons with the contralateral RFs are located throughout areas 3b and 3a, but those with ipsilateral and bilateral RFs are located near the 3a-3b border. Of orofacial neurons, 52% were mastication-related neurons (MRNs) which showed changes in activity during mastication. Over 80% of MRNs showed activity changes following the masticatory rhythm. Many MRNs had RFs in the perioral and tongue region. After lesioning the perioral (PL-cats) or tongue (TL-cats) projection area with kainic acid injec tion (1%. 2 mu l). changes in orofacial behaviors were examined. In PL-cats a delay in the start of mastication and the dropping of food from the mouth were observed. In TL-cats there was a rapid lengthening of the masticatory movement period. In both groups, the pattern of jaw movements remained unchanged. Perioral and tongue MRNs in motor cortex of PL and TL-cats decreased, and much MRN activity in PL-cats were irregular. Thus, the present results indicate that sensory information from the perioral or tongue region is essential for the control of tension in the perioral region and of masticatory movements.