NEUROPHYSIOLOGIC PROPERTIES OF THE SUPRATRIGEMINAL NUCLEUS

Abstract

The neurons responding to the mandibular muscle deformation were explored in the supratrigeminal nucleus region above the trigeminal motor nucleus, and the response pattern of these neurons were analyzed.1. All of the neurons in the supratrigeminal nucleus showed a background activity, and it means that steady impulses f rom the jaw muscles flow into this nucleus. Def ormation of the muscle spindle of the jaw closing muscles activated these background activities.2. In the supratrigeminal nucleus three different types of interneurons which responded to the Ia afferents from the jaw closing muscles were clearly identified. The first type of cell is the M-Cell which responded only to the mechanical deformation of the masseter muscle, the second is the T-Cell, which responded only to the temporalis muscle. The third cell is the M·TCell which is the fundamental cells in the nucleus and responded to both the masseter and temporalis muscles.3. The M · T-Cell showed the summated response when the masseter and temporalis muscles were stimulated at the same time. These interneurons were not affected at all by afferent impulses from the antagonistic muscle. Fifty-six cells out of explored 58 cells in the nucleus were identified as the M · T-Cell, and one M-Cell and one T-Cell were identified, respectively. The M · T-Cell with the activity coefficient Ak=1 is the fundamental cells in this nucleus.