An investigation into the behavioral effects of targeted memory reactivation during sleep on sensorimotor skill performance

Abstract

Background. Memory consolidation occurs during sleep, providing an opportunity to enhance upper extremity (UE) function in people with residual impairments post-stroke. Targeted memory reactivation (TMR) has been used to enhance this process, which involves pairing auditory cues with task performance and subsequent cue replay during sleep. TMR application during sleep leads to increased task-related brain network connectivity and behavioral performance in healthy young adults. Yet it remains unknown whether TMR can enhance sensorimotor performance in individuals with stroke. Methods. Healthy younger and older adults and individuals with chronic stroke were trained on a non-dominant (or non-paretic) UE throwing task before a period of waking or sleeping consolidation, with some receiving TMR throughout the consolidation period. Study 1 involved the use of TMR throughout the first two slow wave sleep periods over a full night of sleep with young adults. Studies 2, 3, and 4 investigated whether TMR throughout a one-hour nap was sufficient to influence sensorimotor performance in young adults, older adults, and people with a history of stroke, respectively. Results. All studies found that TMR application during sleep enhanced sensorimotor performance. In addition, TMR during wake did not influence sensorimotor performance (Studies 1 and 2), and enhanced performance of a cognitive aspect of the trained task (Study 2). Additional generalization and transfer tests helped to support the hypothesis that TMR enhanced a task-specific motor program, as improvements were seen within the trained task but not un-trained, but similar tasks. Lastly, sleep alone appears to stabilize sensorimotor performance variability, but this process demonstrates an age-related decline. Conclusion. This dissertation has shown that the use of TMR during sleep is a useful method for enhancing sensorimotor performance in healthy young and old adults, as well as individuals with a history of stroke. Future research may lead to an adjunct to traditional physical rehabilitation protocols.