Hand and arm function is often significantly impaired in stroke patients, making recovery
of these functions a primary goal in stroke rehabilitation. Despite advances in acute
stroke thera-pies, more than 50% of stroke survivors continue to experience motor
deficits, particularly in hand and arm function, which negatively impacts their quality
of life. The integrity of neural networks, especially the frontoparietal network, plays a
central role in motor control, and has been shown to be altered after stroke.
Transcranial alternating current stimulation (tACS) offers a promis-ing approach to
modulate these brain network connections, potentially influencing motor func-tion in
stroke patients.
In a randomized, controlled, triple-blind, crossover design, this study investigates the
effects of 24Hz bifocal tACS on functional connectivity between the ipsilesional anterior
intraparietal sulcus (aIPS) and ventral premotor cortex (PMv) in stroke patients during
the subacute to chronic recovery phase. Each patient will receive three types of
stimulation-(i) in-phase tACS, (ii) out-of-phase tACS, and (iii) sham stimulation-in a
randomized order, with a one-week washout pe-riod between sessions to avoid carryover
effects. During in-phase tACS, 24Hz stimulation over aIPS and PMv will be in phase;
during out-of-phase stimulation, the phase across sights will vary by 180 degrees.
Bifocal tACS will be delivered using two four-electrode montages centered over the aIPS
and PMv of the lesioned hemisphere for approximately 21 minutes per session. During each
session, patients will perform a Reach-to-Grasp (RTG) task three times: before
stimulation, during stimu-lation, and after stimulation. Patients will perform both a
pinch grip and a whole-hand grasp during the RTG task. EEG data will be collected pre-
and post-stimulation, while kinematic meas-urements will also be recorded during the
stimulation task. To minimize skin sensations under the electrodes and improve blinding,
a local anesthetic consisting of lidocaine and prilocaine will be applied prior to
electrode placement. Clinical assessments as well as structural and func-tional imaging
will be obtained to characterize each patient.
The investigators hypothesize that 24Hz bifocal tACS on the frontoparietal network alters
its connectivity compared to sham stimulation.
This study seeks to enhance the understanding of functional coupling within the
frontoparietal network, aiming to establish bifocal tACS as a targeted and innovative
therapy to improve motor function in stroke patients.