SACCADIC MOTOR PLANNING BY INTEGRATING VISUAL INFORMATION AND PRE-INFORMATION ON NEURAL DYNAMIC FIELDS

A functional model of target selection in the saccadic system is prese nted, incorporating elements of visual processing, motor planning, and motor control. We address the integration of visual information with pre-information, which is provided by manipulating the probability tha t a target appears at a certain location. This integration is achieved within a dynamic representation of planned eye movement which is mode led through distributions of activation on a topographic field. Visual input evokes activation, which is also constrained by lateral interac tion within the field and by preshaping input representing pre-informa tion. The model describes target selection observable in paradigms in which visual goals are presented at more than one location. Specifical ly, we model the transition from averaging, where endpoints of first s accades fall between two visual target locations, to decision making, where endpoints of first saccades fall accurately onto one of two simu ltaneously presented visual targets. We make predictions about how met rical biases of first saccades are induced by pre-information about ta rget locations acquired by learning. When coupled to a motor control s tage, activation dynamics on the planning level contribute to stabiliz ing gaze under fixation conditions. The neurophysiological relevance o f our functional model is discussed.