Increasing Attentional Load Boosts Saccadic Adaptation.

PURPOSE Visual exploration relies on saccadic eye movements and attention processes. Saccadic adaptation mechanisms, which calibrate the oculomotor commands to continuously maintain the accuracy of saccades, have been suggested to act at downstream (motor) and upstream (visuoattentional) levels of visuomotor transformation. Conversely, whether attention can directly affect saccadic adaptation remains unknown. To answer this question, we manipulated the level of attention engaged in a visual discrimination task performed during saccadic adaptation. METHODS Participants performed low or high attention demanding orientation discrimination tasks on largely or faintly oriented Gabor patches, respectively, which served as targets for reactive saccades. Gabor patches systematically jumped backward during eye motion to elicit an adaptive shortening of saccades, and replaced 50 msec later (100 msec in two subjects) by a mask. Subjects judged whether Gabors' orientation was "nearly horizontal" versus "nearly vertical" (low attention demanding) or "slightly left" versus "slightly right" (high attention demanding), or made no discrimination (control task). RESULTS We found that the build-up and the retention of adaptation of reactive saccades were larger in the "high attention demanding" condition than in the "low attention demanding" and the no-discrimination control conditions. CONCLUSIONS These results indicate that increasing the level of attention to the perceptual processing of otherwise identical targets boosts saccadic adaptation, and suggest that saccadic adaptation mechanisms and attentional load effects may functionally share common neural substrates.