Divided attention and manual visuomotor control in stroke: a combined dual-task and eye movement study.

Background: Daily manual tasks require cognitive-motor interactions. There is limited research on cognitive-motor dual-tasks involving the upper extremity. In this study we used a manual visuomotor dual-task to measure post-stroke cognitive-motor impairments. Given previous evidence of impaired cognitive-motor interaction in stroke we hypothesized that the presence of enhanced dual-task cognitive load will impact motor performance in stroke patients. We also hypothesized that this dual-task effect would be greater in stroke patients compared to healthy controls. We also explored whether cognitive-motor impairments observed in these single- and dual-task conditions would relate to deficits in manual dexterity.

Methods: 30 chronic stroke participants (29.77 ± 35.39 months post-stroke) with mild-to-moderate hemiparesis without cognitive impairment (global screening test) and 30 age-matched healthy subjects performed a visuomotor grip force-tracking task in single- and dual-task conditions, requiring divided attention (resisting visual distraction) and working memory (mental addition of transiently displayed numbers). Gaze was simultaneously recorded to probe cognitive performance through saccades. Dexterity impairments were separately quantified using a kinetic device.

Results: Stroke patients had increased visuomotor tracking error but did not show significantly increased change in visuomotor tracking error during the dual-task, with no significant difference between single task condition vs. divided attention or vs. working memory dual-task conditions. In contrast, age-matched healthy controls did show the expected difference with significantly higher dual-task force-tracking error. The between-group analysis only revealed a significant group difference (Stroke vs. Control) with stroke patients producing twice as much tracking error in both single and dual-task conditions. Stroke participants showed significantly reduced dual-task saccade modulation, with a reduced difference in saccades to displayed numbers (similar in both groups) vs. to distractors (higher in stroke) (median ± IQR: stroke 14.6 ± 18.75%; controls: 26.4 ± 32.41%). Non-inhibited saccades to distractors explained certain dexterity group differences (force control and timing of finger movements).

Conclusion: The visuomotor force-tracking error, although increased, did not show enhanced cognitive-motor interaction in stroke. However, the task-related saccade analysis did detect impaired divided attention post-stroke, that may contribute to impaired dexterity, particularly in tasks requiring on-line sensorimotor integration. Upper limb dual-tasking practice may be relevant for engaging attention and enhancing post-stroke activities in daily life. Trial registration ClinicalTrials.gov ID NCT05454748.