C. Pantle et N. Dieringer, SPATIAL TRANSFORMATION OF SEMICIRCULAR CANAL SIGNALS INTO ABDUCENS MOTOR SIGNALS - A COMPARISON BETWEEN GRASS FROGS AND WATER FROGS, Journal of comparative physiology. A, Sensory, neural, and behavioral physiology, 182(4), 1998, pp. 475-487
The spatial transformation of semicircular canal signals to extraocula
r motor signals was studied by recording abducens nerve responses in g
rass and water frogs. Both species have similar vestibular canal coord
inates but dissimilar orientations of their optic axes. Before sinusoi
dal oscillation in darkness the static head position was systematicall
y altered to determine the planes of head oscillation in pitch and rol
l associated with minimal abducens nerve responses. Measured data and
known canal plane vectors were used to calculate the abducens response
vector in canal coordinates. The abducens vector deviated from the ho
rizontal canal plane vector in grass frogs by 15 degrees and in water
frogs by 34 degrees but was aligned with the pulling direction of the
lateral rectus muscle in each of the two species. Lesion experiments d
emonstrated the importance of convergent inputs from the contralateral
horizontal and anterior semicircular canals for the orientation of th
e abducens response vector. Thus, the orientation of the optic axis an
d the pulling directions of extraocular muscles are taken into account
by the central organization of vestibule-ocular reflexes. Horizontal
and vertical canal signals are combined species-specifically to transf
orm the spatial coordinates of sensory signals into appropriate extrao
cular motor signals.