A CROSS-COUPLING MODEL OF VERTICAL VERGENCE ADAPTATION

Vertical disparity vergence aligns the two eyes in response to vertica l misalignment (disparity) of the two ocular images, An adaptive respo nse to vertical disparity vergence is demonstrated by the continuation of vertical vergence when one eye is occluded, The adaptive response is quantified by vertical phoria, the eye alignment error during monoc ular viewing. Vertical phoria can be differentially adapted to vertica l disparities of opposite sign located at two positions along the hori zontal or vertical head-referenced axes, Vertical phoria aftereffects vary in amplitude as the eyes move from one adapted direction of gaze to another along the adaptation asis. A cross-coupling model was devel oped to account for the spatial variations of vertical phoria aftereff ects. The model is constrained according to both single cell recording s of eye position sensitive neurons, and eye position measurements dur ing and following adaptation, The vertical phoria is computed by scali ng the activities of eye position sensitive neurons and converting the scaled activities into a vertical vergence signal, The three componen ts of the model are: neural activities associated with conjugate eye p osition, cross-coupling weights to scale the activities, and vertical vergence transducers to convert the weighted activities to vertical ve rgence. The model provides a biologically plausible mechanism for vert ical vergence adaptation.