Gaze locations affect explicit process but not implicit process during visuomotor adaptation

Abstract

The role of vision in implicit and explicit processes involved in adaptation to novel visuomotor transformations is not well-understood. We manipulated subjects' gaze locations through instructions during a visuomotor rotation task that established a conflict between implicit and explicit processes. Subjects were informed of a rotated visual feedback (45° counterclockwise from the desired target) and instructed to counteract it by using an explicit aiming strategy to the neighboring target (45° clockwise from the target). Simultaneously, they were instructed to gaze at either the desired target (target-gaze group), the neighboring target (hand-target-gaze group), or anywhere (free-gaze group) during aiming. After initial elimination of behavioral errors caused by strategic aiming, the subjects gradually overcompensated the rotation in the early practice, thereby increasing behavioral errors (i.e., a drift). This was caused by an implicit adaptation overriding the explicit strategy. Notably, prescribed gaze locations did not affect this implicit adaptation. In the late practice, the target-gaze and free-gaze groups reduced the drift, whereas the hand-target-gaze group did not. Furthermore, the free-gaze group changed gaze locations for strategic aiming through practice from the neighboring target to the desired target. The onset of this change was correlated with the onset of the drift reduction. These results suggest that gaze locations critically affect explicit adjustments of aiming directions to reduce the drift by taking into account the implicit adaptation that is occurring in parallel. Taken together, spatial eye-hand coordination that ties the gaze and the reach target influences the explicit process but not the implicit process.

Evidence for distinct brain networks in the control of rule-based motor behavior

“…We suggest that these additional eye movements were performed to enable the recoupling of gaze and cursor/hand location to generate and maintain an accurate difference vector (Granek et al, 2012;Shadmehr and Wise, 2005). Free gaze toward the visual target has been associated with the onset of error reduction during decoupled visuomotor learning, implying the influence of explicit gaze location strategies on implicit visuomotor learning (Rand and Rentsch 2015). It appears that the visuomotor adaptation suppressed its generalization to the horizontal targets, a situation in which it was possible to use an explicit, strategic rule to guide movement in some parts of the workspace.…”

Eye-Hand Coordination during Visuomotor Adaptation with Different Rotation Angles: Effects of Terminal Visual Feedback

“…Similar to previous studies [16,21,35–38], at the beginning of each trial, participants were guided to the SP by one or two out of four red arrows pointing to the left, right, up, and down, appearing in the margins of the monitor. The idea behind this procedure was to guide participants to the SP without providing visual feedback of specific hand positions.…”

“…Afterwards, the participants performed the pre-test explicit-knowledge, which examined the baseline level of participants’ explicit knowledge of reaching direction to the target. For this purpose, we used a procedure similar to the ones used in previous studies [16,21,35,38,39]. The SP and the target were presented together with a line starting from the SP.…”

“…Adaptive change of gaze locations associated with the execution of hand movements was further examined in terms of gaze incidences at various areas of the workspace, similar to our previous study [21]. We defined 5 gaze areas for this analysis: the target (T) area, the hand-target (HT) area, the inverted-target (IT) area, the SP area, and the other area (Fig 2).…”

“…Such a location would likely be the final position of reaching movement that counters the applied rotation. This is so because our previous study showed that gazes naturally went to that direction when participants were informed of the nature of a visuomotor rotation from the start and instructed to apply an explicit strategy to counter it [21]. Therefore, when explicit adjustments of reach direction are gradually established through learning, the gaze pattern should also be gradually adjusted toward that direction.…”