Address for correspondence: Dr. Yutaka Hirata, Department of Electronic Engineering, Chubu University College of Engineering, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan. Voice: +81-568-51-9476; fax: +81-568-51-1478.
yutaka{at}isc.chubu.ac.jp
Ann. N.Y. Acad. Sci. 978: 480-495 (2002).
The vestibulo-ocular reflex (VOR) stabilizes the visual image
on the retina during head movement by counter-rotating the eyes
in the head. The VOR is under adaptive control and has been
extensively used to investigate sensorimotor transformations
and motor learning. The cerebellar flocculus (FL) is intimately
involved in VOR motor control and learning, because its sole
output, the Purkinje cell firing pattern, modulates during visual-vestibular
interaction paradigms that induce motor learning, and flocculectomy
impairs the ability to modify the VOR. However, the role of
the FL in VOR motor learning and the possibility of another
neuronal site responsible for learning have been controversial.
Currently, we performed single unit recordings of FL Purkinje
cells during adaptation of the vertical (V) VOR in squirrel
monkeys and used a system identification approach to localize
the adaptable neuronal sites responsible for VVOR motor learning.
We demonstrated that there are multiple adaptive sites: one
upstream or in the FL, another in the non-FL pathway; change
in the former site is in the wrong direction to cause the observed
VVOR gain change, whereas that in the latter site is in the
correct direction. The possibility that FL Purkinje cells convey
an error signal to their target neurons that can be used to
aid learning is discussed.
