BACKGROUND: In healthy subjects, preparation to move is accompanied by motor cortical disinhibition. Poor control of intracortical inhibitory function in the primary motor cortex (M1) might contribute to persistent abnormal motor behavior in the paretic hand after chronic stroke. METHODS: Here, we studied GABAergic short intracortical inhibition (SICI) in the ipsilesional M1 in well-recovered chronic stroke patients (n = 14; 63.8 +/- 3.0 years) engaged in preparation to move the impaired hand in a reaction time paradigm. RESULTS: The main finding was an abnormal persistence of SICI in the ipsilesional M1 during movement preparation that was absent in age-matched controls (n = 14). Additionally, resting SICI was reduced in the patient group relative to controls. CONCLUSIONS: Our findings document a deficit of dynamic premovement modulation of intracortical inhibition in the ipsilesional primary motor cortex of patients with chronic stroke. This abnormality might contribute to deficits in motor control of the paretic hand, presenting a possible target for correction in the framework of developing novel therapeutic interventions after chronic stroke.
