BEHAVIORAL-ANALYSIS OF SIGNALS THAT GUIDE LEARNED CHANGES IN THE AMPLITUDE AND DYNAMICS OF THE VESTIBULOOCULAR REFLEX

We characterized the dependence of motor learning in the monkey vestib ule-ocular reflex (VOR) on the duration, frequency, and relative timin g of the visual and vestibular stimuli used to induce learning. The am plitude of the VOR was decreased or increased through training with pa ired head and visual stimulus motion in the same or opposite direction s, respectively. For training stimuli that consisted of simultaneous p ulses of head and target velocity 80-1000 msec in duration, brief stim uli caused small changes in the amplitude of the VOR, whereas long sti muli caused larger changes in amplitude as well as changes in the dyna mics of the reflex. When the relative timing of the visual and vestibu lar stimuli was varied, brief image motion paired with the beginning o f a longer vestibular stimulus caused changes in the amplitude of the reflex alone, but the same image motion paired with a later time in th e vestibular stimulus caused changes in the dynamics as well as the am plitude of the VOR. For training stimuli that consisted of sinusoidal head and visual stimulus motion, low-frequency training stimuli induce d frequency-selective changes in the VOR, as reported previously, wher eas high-frequency training stimuli induced changes in the amplitude o f the VOR that were more similar across test frequency. The results su ggest that there are at least two distinguishable components of motor learning in the VOR. One component is induced by short-duration or hig h-frequency stimuli and involves changes in only the amplitude of the reflex. A second component is induced by long-duration or low-frequenc y stimuli and involves changes in the amplitude and dynamics of the VO R.