Throughout our lives the nervous system must constantly monitor and adjust the relationship between visual input and oculomotor output. Several times a minute a target is selected from the vast array of objects in our visual environment, and a high velocity eye movement called a saccade moves the eye efficiently and accurately to its goal. Development, aging, injury, and disease each make their special demands on the saccadic system. There is also a need for continuous fine tuning that underlies our ability to judge depth, strike a ball, or play video games. Mechanisms of recalibration are a factor in success of strabismus surgery and adjustments to contact lenses. The saccadic system has evolved at least one mechanism, and perhaps many mechanisms, that can adjust its performance in response to these demands. The long term objective of this proposal is to contribute to our understanding of such mechanisms. A model is presented that is consistent with many observations of saccadic adjustments (modified from Deubel, 1987). The model considers the adaptive mechanism as a array of adaptive controllers that are capable of independently adjusting the gain of the output of subunits coding the motor error signal. The subunits representing motor error both the amplitude and direction of the needed movement. The dimensions of motor error are mapped onto a single binocular map controlling conjugate movement. Seven specific experiments are proposed to verify aspects of this model. *Are there separate arrays of adaptive controllers for the two eyes? *To what degree do elements within the array of adaptive controllers interact? *Do adaptive controllers modify movements specified in vectors or in horizontal and vertical components? *Do the adaptive controllers effect a change in the motor error signal? *Is the adaptive process dependent on a single derived from corrective saccades? *Do movements of the visual background contribute to adaptive changes? *Do visumotor systems other than the saccadic have access to modifiable motor error mapping? Recalibration will be studied using a technique of precisely controlled visuomotor errors called intrasaccadic feedback. This method provides several advantages: 1) it mimics the errors that occur during ordinary dysmetria, 2) it produces rapid and reversible changes, 3) it can be used in intact monkeys and humans, and 4) it produces amplitude changes in dynamically normal saccades.
