Abstract
GOAL Perceptual learning (PL) studies find that practice improves motion direction discrimination. We previously showed that PL affects perceived motion direction (Szpiro-Grinberg, Spering, Carrasco; ECVP 2011). However, it is unknown whether this perceptual effect would transfer to motor actions. Using a direction estimation task, we examined PL and its effect on the direction of smooth pursuit eye movements. METHOD We presented a random-dot kinematogram (75% motion coherence, drifting at 10º/s) and after stimulus offset asked observers to estimate its motion direction by manually adjusting the angle of an arrow shown on the screen. All observers underwent a pre-test (day 1), training sessions (days 2-4) and a post-test (day5). During the testing sessions, we presented stimuli moving rightward or leftward along the horizontal axis or in a direction deviating ±3º from horizontal. During the training sessions, we only presented stimuli moving to one side. We conducted two experiments that differed only in the procedure of the testing sessions: in Experiment 1, observers fixated throughout the stimulus presentation; in Experiment 2, observers tracked the stimulus motion direction with their eyes. Both groups performed the estimation task. In the training sessions, all observers fixated during the stimulus presentation and then performed the estimation task. Comparing these experiments enabled us to isolate whether potential effects of PL on direction estimation would also transfer to pursuit directions. RESULTS In both experiments and for all directions PL produced an overestimation of motion direction away from the perceived horizontal. This result reveals that PL shifts perceived directions even when viewed under different retinal stimulation (fixation/pursuit). Moreover, in Experiment 2, pursuit directions also showed overestimation, as if the eyes followed the perceived directions. The results show that training perception is sufficient to alter pursuit direction, thus indicating that PL can transfer to a smooth pursuit motor response.
Meeting abstract presented at VSS 2012