CONTEXT-SPECIFIC ADAPTATION OF VERTICAL VERGENCE TO CORRELATES OF EYEPOSITION

Vertical phoria (vertical vergence in the absence of binocular feedbac k) can be trained to vary with non-visual cues such as vertical conjug ate eye position, horizontal conjugate eye position and horizontal ver gence. These prior studies demonstrated a low-level association or cou pling between vertical: vergence and several oculomotor cues. As a tes t of the potential independence of multiple eye-position cues for vert ical vergence, context-specific adaptation experiments were conducted in three orthogonal adapting planes (midsagittal, frontoparallel, and transverse). Four vertical disparities in each of these planes were as sociated with various combinations of two specific components of eye p osition. Vertical disparities in the midsagittal plane were associated with horizontal vergence and vertical conjugate eye position; vertica l disparities in the frontoparallel plane were associated with horizon tal and vertical conjugate eye position; and vertical disparities in t he transverse plane were associated with horizontal vergence and horiz ontal conjugate eye position. The results demonstrate that vertical ve rgence can be adapted to respond to specific combinations of two diffe rent sources of eye-position information. The results are modeled with an association matrix whose inputs are two classes of eye position an d whose weighted output is vertical vergence. (C) 1997 Elsevier Scienc e Ltd.