Incidental learning of a visuo-motor sequence modulates saccadic amplitude: Evidence from the serial reaction time task

This study examined the changes in saccadic amplitude associated with learning a visual sequence. The oculomotor system gradually adjusts saccadic parameters when tracking a visual stimulus, which has a predictable trajectory. In these contexts, the change in saccadic amplitudes leads to predictive fixations. That is, fixations made to a position in the visual field, where a visual stimulus is anticipated to appear. This study tested whether learning a sequence of visual target movements on the serial reaction time (SRT) task would affect saccadic amplitudes and in turn lead to predictive fixations. Participants in this study were 40 healthy adults who completed the SRT task. Both manual reaction times (RTs) and eye movements were recorded. Analyses of manual RT data showed that at the group level, the sequence was learnt. Analyses of the oculomotor data revealed saccadic amplitudes decreased, following repeated exposures to the visual sequence. Also, increasingly more accurate predictive fixations were observed, following multiple exposures to the sequence. Additional analyses revealed sequence learning related changes in manual RTs, and saccadic amplitudes were not correlated. This study demonstrates the oculomotor system can acquire information about the sequence on the SRT task to update saccadic amplitudes. The nonsignificant correlation between manual RTs and saccadic amplitudes may be indicating sequences are represented differently by the manual and oculomotor systems.