Dependence of cat vestibulo-ocular reflex direction adaptation on animal orientation during adaptation and rotation in darkness

Four series of experiments investigated how adaptive changes in direction of the cat's vestibulo-ocular reflex (VOR) vary with position of the animal during adaptive training and postadaptive testing. In all experiments VOR was measured electrooculographically during rotations about earth-horizontal and vertical axes in the dark before and after 2 h of adaptation in which 0.25 Hz sinusoidal whole body rotation about a horizontal/vertical axis was paired with synchronous 0.25 Hz rotation of a visual pattern about anvertical/horizontal axis, respectively. In upright sagittal (US) experiments, coupling of pitch rotation with visual pattern rotation about an earth vertical axis yielded an adaptive horizontal VOR response to pitch rotation whose gain had a local maximum at 0.25–0.5 Hz plus a sustained rise for frequencies below 0.1 Hz. When post-tests were done with the animal rolled 90° onto its side and rotated about the earth vertical axis (pitch relative to the cat), the low frequency rise was eliminated and the 0.25 Hz peak was reduced. In on side sagittal (SS) experiments, where training was done in the latter (on side) position, training produced only the 0.25 Hz peak without the low frequency rise, indicating that the rise is due to coupling of otolith input to horizontal VOR. Again the 0.25 Hz peak was reduced when testing was done with the cat oriented 90° from the training position (in the US position). This indicates that the cross-coupled canal-ocular reflex response is modulated or gated by the position of the animal with respect to gravity. Similar results were obtained in upright horizontal (UH) and on side horizontal (SH) experiments where rotations were oriented to activate the horizontal rather than the vertical canals.