Modulation of the BOLD-response in early recovery from sensorimotor stroke.

Abstract

The BOLD signal in functional MRI (fMRI) is closely related to neural activity. To investigate if this relationship is disrupted after ischemic stroke. BOLD activity during tactile exploration of objects was measured with fMRI at 1 week (subacute), 2 to 4 weeks (early chronic), and after 1 month (chronic) after the first completed brain infarction affecting the sensorimotor cortex in eight patients. Functional integrity of the motor cortical output system was assessed with transcranial magnetic stimulation (TMS). Early after infarction the BOLD-response occurred in the adjacent cortical vicinity related to finger movements of the affected hand. However, during the early chronic stage there was a transient lack of this activation despite clinical improvement of hand function and preserved motor evoked potentials. The BOLD activity reappeared after further improvement in the chronic stage. Our findings suggest a transient hemodynamic-electrical decoupling in the post-ischemic cerebral cortex during the early phase of spontaneous clinical recovery.