The Journal of Neuroscience, April 1, 2003, 23(7):2971
Premotor Neurons Encode Torsional Eye Velocity during
Smooth-Pursuit Eye Movements
Dora E.
Angelaki and
J. David
Dickman
Department of Neurobiology, Washington University School of
Medicine, and Hearing Research Department, Central Institute for the
Deaf, St. Louis, Missouri 63110
Responses to horizontal and vertical ocular pursuit and head and
body rotation in multiple planes were recorded in eye
movement-sensitive neurons in the rostral vestibular nuclei (VN) of two
rhesus monkeys. When tested during pursuit through primary eye
position, the majority of the cells preferred either horizontal or
vertical target motion. During pursuit of targets that moved
horizontally at different vertical eccentricities or vertically at
different horizontal eccentricities, eye angular velocity has been
shown to include a torsional component the amplitude of which is
proportional to half the gaze angle ("half-angle rule" of
Listing's law). Approximately half of the neurons, the majority of
which were characterized as "vertical" during pursuit through
primary position, exhibited significant changes in their response gain
and/or phase as a function of gaze eccentricity during pursuit, as if
they were also sensitive to torsional eye velocity. Multiple linear
regression analysis revealed a significant contribution of torsional
eye movement sensitivity to the responsiveness of the cells.
These findings suggest that many VN neurons encode three-dimensional
angular velocity, rather than the two-dimensional derivative of eye
position, during smooth-pursuit eye movements. Although no clear
clustering of pursuit preferred-direction vectors along the
semicircular canal axes was observed, the sensitivity of VN neurons to
torsional eye movements might reflect a preservation of similar
premotor coding of visual and vestibular-driven slow eye movements for both lateral-eyed and foveate species.
Key words:
eye movement; vestibulo-ocular; vergence; kinematics; torsion; smooth pursuit; coordinate frame; three-dimensional; sensorimotor
Copyright © 2003 Society for Neuroscience 0270-6474/03/2372971-09$05.00/0