Cortical Sensorimotor Integration as a Neural Origin of Impaired Grip Force Direction Control following Stroke.

BACKGROUND: Stroke is a major cause of disability worldwide. Upper limb impairment is prevalent after stroke. One of the post-stroke manifestations is impaired grip force directional control contributing to diminished abilities to grip and manipulate objects necessary for activities of daily living. The objective of this study was to investigate the neural origin of the impaired grip force direction control following stroke. Due to the importance of online adjustment of motor output based on sensory feedback, it was hypothesized that grip force direction control would be associated with cortical sensorimotor integration in stroke survivors.

METHODS: Ten chronic stroke survivors participated in this study. Cortical sensorimotor integration was quantified by short latency afferent inhibition (SAI), which represents the responsiveness of the primary motor cortex to somatosensory input. Grip force direction control was assessed during paretic grip.

RESULTS: Grip force direction control was significantly associated with SAI. This relationship was independent of sensory impairment level.

CONCLUSIONS: Cortical sensorimotor integration may play a significant role in the grip force direction control important for gripping and manipulating objects with the affected hand following stroke. This knowledge may be used to inform personalized rehabilitation treatment. For example, for patients with impaired grip force direction control, behavioral therapy focusing on feedback motor control, augmented by use of brain stimulation to reinforce cortical sensorimotor integration such as paired associative stimulation, may be applied.