Behavioral and neurophysiological mechanisms underlying motor skill learning in patients with post-stroke hemiparesis.

OBJECTIVE: Given the presence of execution deficits after stroke, it is difficult to determine if patients with stroke have deficits in motor skill learning with the paretic arm. Here, we controlled for execution deficits while testing practice effects of the paretic arm on motor skill learning, long-term retention, and corticospinal excitability.

METHODS: Ten patients with unilateral stroke and ten age-matched controls practiced a kinematic arm skill for two days and returned for retention testing one-day and one-month post-practice. Motor skill learning was quantified as a change in speed-accuracy tradeoff from baseline to retention tests. Transcranial magnetic stimulation (TMS) was used to generate an input-output curve of the ipsilesional motor cortex (M1), and measure transcallosal inhibition from contralesional to ipsilesional M1.

RESULTS: While the control group had greater overall accuracy than the stroke group, both groups showed comparable immediate and long-term improvements with practice. Skill improvements were accompanied by greater excitability of the ipsilesional corticospinal system and reduced transcallosal inhibition from contralesional to ipsilesional M1.

CONCLUSIONS: When execution deficits are accounted for, patients with stroke demonstrate relatively intact motor skill learning with the paretic arm. Paretic arm learning is accompanied by modulations in corticospinal and transcallosal mechanisms.

SIGNIFICANCE: Functional recovery after stroke relies on ability for skill learning and the underlying mechanisms.