A gaze-contingent paradigm for studying continuous saccadic adaptation

Saccadic eye movements are used to quickly and accurately orient our fovea within our visual field to obtain detailed information from various locations. The accuracy of these eye movements is maintained throughout life despite constant pressure on oculomotor muscles and neuronal structures by growth and aging; this maintenance appears to be a product of an adaptive mechanism that continuously accounts for consistent post-saccadic visual error, and is referred to as saccadic adaptation. In this paper, we present a new paradigm to test saccadic adaptation under circumstances that more closely resemble natural visual error in everyday vision, whereas previous saccadic adaptation paradigms study adaptation in a largely restricted form. The paradigm achieves this by positioning a stimulus panel atop an identically colored background relative to the gaze position of the participant. We demonstrate the paradigm by successfully decreasing participants' saccadic amplitudes during a common visual search task by shifting the stimulus panel in the opposite direction of the saccade by 50% of the saccadic amplitude. Participants' adaptation reached approximately 60% of the 50% back-shift during the adaptation phase, and was uniformly distributed across saccadic direction. The adaptation time-course found using the new paradigm is consistent with that achieved using previous paradigms. Task-performance results and the manner in which eye movements changed during adaptation were also analyzed.