Rostral fastigial nucleus activity in the alert monkey during three-
dimensional passive head movements.
Siebold, C., L. Glonti, St. Glasauer, U. Bttner.
Dept. of Neurology and Center for Sensorimotor Research, Ludwig
Maximilians University, D 81377 Munich, Germany.
APStracts 3:0246N, 1996.
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