Responses of neurons in nucleus supratrigeminalis to sinusoidal jaw movements in the cat

Abstract

Single neurons in the mesencephalic nucleus of the fifth nerve and in the rostral brain stem of barbiturate-anesthetized cats were studied in terms of their response to sinusoidal jaw movements at different frequencies and amplitudes. Units were quantitatively characterized by magnitude and phase of their firing rate modulation as a function of frequency, the linearity of their response at 5 Hz, and the variability of the interpsike intervals. Units were qualitatively characterized in terms of their response to gentle palpation of jaw muscles. Neurons were found in the nucleus supratrigeminalis that were selectively driven by jaw movement and that responded to gentle palpation to one or more ipsilateral jaw muscles. The magnitude of the sensitivity of these neurons as a function of frequency was not significantly different from cells of the mesencephalic nucleus of the fifth nerve. The phase of the sensitivity was, however, significantly more advanced than were those cells at all but the highest frequencies. The typical interspike interval variability of cells in nucleus supratrigeminalis was about 40% of the mean interval, whereas that variability of neurons of the mesencephalic nucleus of the fifth nerve was only about 10% of the mean interval. Supratrigeminal cells could relay jaw proprioceptive information to the cerebellum or thalamus.