Neurofunctional correlates of eye to hand motor transfer

Abstract

This work investigates the transfer of motor learning from the eye to the hand and its neural correlates by using functional magnetic resonance imaging (fMRI) and a sensorimotor task consisting of the continuous tracking of a virtual target. In pretraining evaluation, all the participants (experimental and control group) performed the tracking task inside an MRI scanner using their right hand and a joystick. After which, the experimental group practiced an eye-controlled version of the task for 5 days using an eye tracking system outside the MRI environment. Post-training evaluation was done 1 week after the first scanning session, where all the participants were scanned again while repeating the manual pretraining task. Behavioral results show that the training in the eye-controlled task produced a better performance not only in the eye-controlled modality (motor learning) but also in the hand-controlled modality (motor transfer). Neural results indicate that eye to hand motor transfer is supported by the motor cortex, the basal ganglia and the cerebellum, which is consistent with previous research focused on other effectors. These results may be of interest in neurorehabilitation to activate the motor systems and help in the recovery of motor functions in stroke or movement disorder patients.

Keywords: basal ganglia; brain mapping; cerebellum; eye movements; fMRI; motor activity; motor cortex; neurorehabilitation; transfer of learning; upper limb.

Figure 1

Experimental design. Participants controlled the red circle to track the gray circle (target) that was moving horizontally in a sine–cosine waveform (top of the figure). Gray/red arrows and dotted curve depict directions of movements and target trajectory, respectively (not visible during the task). In the pretraining and post‐training evaluation, participants performed the continuous tracking task using the right hand during fMRI acquisition. The experimental group also practiced an eye‐controlled version of the tracking task for 5 days outside the MRI scanner using an eye tracking system. fMRI, functional magnetic resonance imaging

Figure 2

(a) Eye tracking accuracy scores show a better performance across training sessions for the ocular train group (p < .05). (b) Hand tracking accuracy scores show a better performance for the ocular train group during the post‐training evaluation. This performance improvement was not observed in the control group. *p < .001. Error bars depict SE

Figure 3

Brain rendering and three axial slice sections (selected at the height of motor cortical, subcortical, and cerebellar regions) showing activations for the all tracking conditions > fixation contrast across all participants (p < .05, FWE voxel‐wise corrected). Numbers near the slices depict the Z MNI coordinate

Figure 4

Neural activations associated to the transfer of motor learning from the eye to the hand. Red voxels: significant activation clusters resulting from the simple effect of day in the ocular train group (post‐training evaluation > pretraining evaluation; no activations were found for the opposite contrast). Yellow voxels: significant activation clusters resulting from the group × day interaction. Common voxels of both contrasts are shown in orange (virtually the same voxels obtained for the simple effect of day); many of which are located in motor regions (e.g., precentral gyrus, basal ganglia, and cerebellum). No significant simple effects of day were found for the control group. Threshold: p < .05 FDR corrected at the voxel level, k = 25 (simple effect of day was inclusively masked with the group × day interaction contrast; uncorrected mask p‐value = .05)