Rostral fastigial nucleus activity in the alert monkey during three- dimensional passive head movements. Siebold, C., L. Glonti, St. Glasauer, U. Bttner. Dept. of Neurology and Center for Sensorimotor Research, Ludwig Maximilians University, D 81377 Munich, Germany.
APStracts 3:0246N, 1996.
ABSTRACT
The fastigial nucleus (FN) receives vestibular information predominantly from Purkinje cells (PCs) of the vermis. The FN in the monkey can be divided in a rostral part, related to spinal mechanisms, and a caudal part with oculomotor functions. In order to understand the role of FN during movements in space single unit activity in alert monkeys was recorded during passive 3- dimensional head movements from rostral FN. Seated monkeys were rotated sinusoidally around a horizontal earth fixed axis (vertical-stimulation) at different orientations 15 apart (including roll, pitch, vertical-canal-plane and intermediate planes). In addition sinusoidal rotations around an earth vertical axis (yaw-stimulus) included different roll and pitch positions (+/- 10,+/-20). The latter positions were also used for static stimulation. 158 neurons in two monkeys were modulated during the sinusoidal vertical search stimulation. The vast majority showed a uniform response pattern: a maximum at a specific head orientation (response vector orientation) and a null-response 90 apart. Detailed analysis was obtained from 111 neurons. Based on their phase relation during dynamic stimulation and their response to static tilt these neurons were classified as vertical semicircular canal (N=79, 71.2%) or otolith (N=25; 22.5%) related. Only 7 neurons did not follow the usual response pattern and were classified as complex neurons. For the vertical canal-related neurons (N=79) all 8 major response vector orientations (ipsilateral or contralateral anterior canal, posterior canal, roll, pitch nose-down and nose-up) were found in the FN on one side. Neurons with ipsilateral orientations were more numerous and on average more sensitive than those with contralateral orientations. The remaining 10 neurons were classified as pitch neurons. Twenty-eight percent of the vertical canal- related neurons also responded to horizontal canal stimulation. None of the vertical canal-related neurons responded to static tilt. Otolith-related neurons (N=25) had a phase relation close to head position and were considerably less numerous than canal-related neurons. Except for pitch all other response vector orientations were found. Seventy percent of these neurons responding during dynamic stimulation also responded during static tilt. The sensitivity during dynamic stimulation was always higher than during static stimulation. Sixty-one percent of the otolith-related neurons responded also to horizontal canal stimulation. These results show that in the fastigial nucleus robust vestibular signals are abundant. Canal-related responses are much more common than otolith-related responses. Although for many canal neurons the responses can be related to single canal planes, canal convergence between vertical but also with horizontal canals is common. 

Received 3 July 1996; accepted in final form 18 October 1996.
APS Manuscript Number J523-6.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996