UNEQUAL SACCADES PRODUCED BY ANISEIKONIC PATTERNS - A MODEL APPROACH

This study addresses a possible mechanism for fast disconjugate adapta tion of binocular horizontal saccades, Disconjugacy of binocular sacca des was elicited by two dichoptically presented, identical but aniseik onic, random checkerboard patterns. Adaptation was achieved with the p atterns at far distance (144 cm), In this condition, which requires a relatively small (8%) size difference of the saccades, a short learnin g period was mandatory for the binocular saccades to become disconjuga te, The saccadic modifications were superimposed on an idiosyncratic p attern of intra-saccadic yoking. A model of saccadic signal generation is described, that has been used to separate the contributions on sac cadic disconjugacy provided by modification of visual inputs processin g, which alters the motor-system inputs, and by modification of the co ntrol system: the adaptation. We identified three major components of the saccadic command (two phasic and one tonic) that contribute and in a specific way to the saccadic yoking and disconjugacy. The model ana lysis proposes that separate control mechanisms exist operating on the se phasic and tonic signals. We show that the saccadic system can gene rate the vergence component shown by our aniseikonic saccades, We disc uss a distributed-parallel implementation of the saccadic system able to provide both the conjugate and disconjugate components of control.