Layer-specific cortical signatures uncover a sensory origin of post-stroke motor dysfunction

Research using high-field functional magnetic resonance imaging (7T fMRI) examined activation of the primary motor cortex across different brain layers in 12 stroke patients and 14 healthy controls. In patients, reduced activation was found in superficial layers (L2/3) and deep layers (L5) during affected hand movement, indicating failure of sensorimotor integration and spinal cord output. In the hemisphere opposite to the stroke, these layers behaved differently: superficial layers (L1) correlated with overall motor outcome, while deep layers (L5/L6) specifically correlated with grip force of the affected hand. The research demonstrated for the first time in humans that stroke does not damage the motor cortex uniformly but reorganizes it at the level of individual layers. These findings suggest that layer-specific imaging can provide prognostic information inaccessible through whole-region measurements and could help stratify motor deficits and guide targeted rehabilitation treatment.