A theoretical analysis of two models of the vestibulo-ocular and optokinetic systems was performed. Each model contains a filter element in the vestibular periphery to account for peripheral adaptation, and a filter element in the central vestibulooptokinetic circuit to account for central adaptation. Both models account for 1 adaptation, i.e. a response decay to a constant angular acceleration input, in both peripheral vestibular afferent and vestibulo-ocular reflex (VOR) responses and 2 the reversal phases of optokinetic after-nystagmus (OKAN) and the VOR and 3 oscillatory behavior such as periodic alternating nystagmus. The two models differ regarding the order of their VOR transfer function. Also, they predict different OKAN patterns following a prolonged optokinetic stimulus. These models have behavioral implications and suggest future experiments.
seen during sustained acceleratory stimuli (Boumans et al. 1983;Brown and Wolfe 1969;Malcolm and Jones 1970; Paige 1983a) nor the reversal in direction that follows the previously mentioned exponential decay in the VOR response to brief angular acceleration (Sills et al. 1978;Aschan and Bergstedt 1955;Jeannerod et al. 1975). Subsequent models of the VOR accounted for these behaviors by the inclusion of an "adaptation operator" (Young and Oman 1969;Malcolm and Jones 1970;Schmid et al. 1971). These operators stored signals in the path between the inner ear and the eye muscles and, because their contents were subtracted from the unadapted output, caused the response decline and undershoot behaviors mentioned above.
Shown in Fig. 1 are block diagrams, based on work by Young and Oman (1969) and Malcolm and Jones (1970), of two models of the VOR that contain adaptation operators. Although the models in Fig. 1