Memory-Guided Reaching: Is It Effortful?

We previously showed that perceived effort during visually guided reaching was altered as task demand varied. Further, self-reported subjective fatigue correlated with perceived effort and reach performance under visually guided conditions. Memory-guided reaching often leads to performance deterioration and can provide insights about the planning and control of reach actions. It is unclear how perceived effort changes during memory-guided reaching and whether self-reported subjective fatigue is associated with perceived effort of memory-guided reaching. Twenty-three young adults performed reach actions under visually- and memory-guided conditions. Perceived effort, reaction time, and endpoint error increased significantly from the visually- to the memory-guided condition. Self-reported subjective fatigue was associated with perceived effort and reach distance error during memory-guided reaching; those with higher levels of fatigue reported greater perceived effort and tended to reach farther when visual information was not available. These findings establish a foundation to examine relationships between subjective fatigue, perceived effort, and reach control.

Motor imagery during movement activates the brain more than movement alone after stroke: a pilot study.

OBJECTIVE: To examine the neural correlates of motor imagery performed in conjunction with movement of the paretic arm after stroke. DESIGN: Cross-sectional, cohort study. SUBJECTS: Seven individuals in the chronic phase of stroke recovery (median (range): age: 58 years (37-73); time post-stroke: 9 months (4-42); upper extremity Fugl-Meyer motor score: 48 (36-64)). METHODS: Participants actively moved the paretic/right arm under two conditions while undergoing functional magnetic resonance imaging. In the motor condition, pronation/supination movements were made in response to a visual cue. In the motor + imagery condition, the same movements were performed in response to a visual cue but the participants were instructed to imagine opening and closing a doorknob during performance of the movement. RESULTS: For the motor condition, the anticipated motor network was activated and included left sensorimotor cortex and right cerebellum. For performance of the same movements during the motor + imagery condition, additional brain regions were significantly engaged including the left inferior parietal lobule and right dorsolateral prefrontal cortex. CONCLUSIONS: The addition of motor imagery to movement may provide a practical, accessible way to modulate activity in both the planning and execution components of the motor network after stroke.