The responses of 47 nucleus prepositus hypoglossi neurons to vestibular optokinetic stimulations in the horizontal plane were recorded in immobilized, pigmented rats. During sinusoidal vestibular stimulation in the dark, type II (62%) and type I (38%) responses were recorded. In addition to the sinusoidal modulation of firing rate, units often showed fast rhythmic increases or decreases in firing (nystagmic modulation). The mean phase of the response relative acceleration measured at 0.025 and 0.2 Hz were 19 and 84 deg., respectively. Some units (25%) showed larger phase-lags. The sensitivities of unit responses at 0.025 and 0.2 Hz were 1.6 and 0.5 spikes X s-1/deg X s-2, respectively. The responses of NPH neurons to binocular optokinetic stimulation were divided in 2 classes: (i) neurons with unidirectional responses (18%) were excited by stimuli moving towards the side of recording and showed no change in firing on oppositely directed stimulation; all of them showed a type II pattern during vestibular stimulation; (ii) bidirectional responses showed an increase in one direction and a decrease in firing for stimulation in the opposite direction. In every case the optokinetic responses were synergistic with the vestibular responses, which consisted of both type I and type II units. On the basis of the directionality of their optokinetic response, the value of their time constants and the shape of their velocity tuning curves, it is suggested that unidirectional type II NPH neurons could serve as relays in the optokinetic pathways between NRTP (or PT) and vestibular neurons. Some other neurons, having time constants particularly long and different for the rising and falling of the response, probably serve other functions.

Download full-text PDF

Source
http://dx.doi.org/10.1016/0006-8993(84)90400-1DOI Listing

Publication Analysis

Top Keywords

responses
9
prepositus hypoglossi
8
hypoglossi neurons
8
vestibular stimulation
8
nph neurons
8
time constants
8
neurons
7
optokinetic
6
vestibular
6
type
6

Similar Publications

Want AI Summaries of new PubMed Abstracts delivered to your In-box?

Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!