Inclusion criteria for aged matched healthy group
- Male or female whose age range between 40 and 75
- no known neurological injuries
Exclusion criteria for aged matched healthy group
- have an orthopedic disorder involving upper limbs;
- have a history of any neurologic disease;
- have any history of epilepsy of the potential participants and/or their family members;
- had an adverse reaction to TMS;
- are unable to consent;
- are pregnant.
Inclusion criteria for stroke group
- male or female hemiparetic chronic stroke survivors;
- age ranging between 40-75 year;
- with single unilateral ischemic or hemorrhagic middle cerebral artery stroke;
- neurologically stable for >6 months;
- have an expectation that current medication will be maintained without changes for at least 3 months. Stable use of anti-spasticity medication (e.g., baclofen, diazepam, tizanidine) is accepted;
- with moderate-to-severe impairments (FMA<45/66);
- with weak wrist extension (i.e., <4 by manual muscle strength test);
- eligible to receive transcranial magnetic stimulation (TMS), and extensor carpi radialis (ECR) motor evoked potential (MEP) must be present in the more affected arm;
- without severe spasticity (Modified Ashworth (MA) <4);
- have not received botulinum toxin on the impaired arm within 3 months.
Exclusion criteria for stroke group
- have an orthopedic disorder involving upper limbs;
- have no measurable MEP elicited in the ECR;
- unable to produce any voluntary ECR EMG activity;
- cognitive impairment sufficient to interfere with informed consent or successful completion of the protocol (Montreal Cognitive Assessment (MoCA) score < 26);
- a history of another neurologic disease;
- a history of vertigo;
- a history of vestibular or cochlear dysfunction;
- have a history of convulsion or a seizure;
- anesthesia of joint position sense in upper limbs;
- are pregnant or have a chance that they might be (self-reported);
- have metal in the brain/skull (except titanium; e.g. splinters, fragments, clips, etc.);
- have cochlear implants;
- have an implanted neurostimulator (DBS, epidural/subdural, VNS);
- have a cardiac pacemaker or intracardiac lines or metal in the body;
- have a medication infusion device;
- are taking any medications to treat mental illness;
- have spinal or ventricular derivations;
- had an adverse reaction to TMS.