Priming of eye movements by masked stimuli

Abstract

In a metacontrast paradigm I investigated how central symbolic and peripheral spatial primes influenced saccadic eye movements initiated by a target stimulus. Saccadic reaction times were a function of angular difference between movement directions indicated by prime and target (congruence). Saccades started earlier with high congruence than with low congruence (priming effect). In incongruent trials, gaze trajectories deviated away from the direction indicated by the prime (prime suppression). The priming effect and prime suppression increased with interstimulus interval between prime and mask. Response speed and congruence predicted the direction of gaze deviations. Gaze deviations towards or away from the prime seemed to reflect the relative timing between the onset of prime-suppression with respect to movement initiation. The effect of primes on saccadic reaction time and metrics were simulated in a neural network model based on the assumption that decision processes and response preparation both rely on population coding as their principle of neural representation. The model accounts for the reaction time data as well as for the observed gaze deviations.