The Motor Effects of Combined Peripheral Nerve Electrical Stimulation and Action Observation on the Affected Hand in People With Stroke

The investigator's previous study (Liu & Au-Yeung, 2017; PMID: 28383292) has demonstrated that 1-hour peripheral nerve stimulation (PNS) applied to the radial and ulnar nerves of the paretic UL of people with chronic stroke can increase transcranial magnetic stimulation (TMS)-evoked excitability of corticomotor pathways in both hemispheres projected to the contralateral first dorsal interosseous (FDI) hand muscle, and also improve dexterity in the paretic hand. This bi-hemispheric effect of PNS suggests that certain additional therapies such as action observation (AO) and motor training should be incorporated to strengthen the plastic corticomotor adaptation specifically for paretic UL control. The hypothesis of this study is that PNS paired with AO would augment task training of the paretic hand by increasing the corticomotor excitability in the lesioned hemisphere for the trained hand muscle in people with stroke, with associated dexterity function improvement. Twenty subjects were recruited by convenience in the community. They then attended an assessment session to evaluate the baseline sensorimotor status of their paretic upper limb. After the clinical tests，the subjects were introduced the assessment procedure for measuring corticomotor excitability with transcranial magnetic stimulation (TMS). After 1-week intermission, the subjects returned for 3 intervention sessions with different protocols including (1)PNS+AO+Training; (2)PNS+AOsham+Training; and (3)PNSsham+AOsham+Training. These 3 intervention sessions were arranged in random sequence for subjects. For "PNS+AO+Training" session, electrical stimulation was applied to the radial and ulnar nerve (PNS) of the paretic arm for 60 minutes. During the last 30 minutes of PNS, action observation (AO) was introduced in which subjects were required to watch a series of video clips. After one hour's PNS+AO, the subjects then proceeded to a 30-minute period of motor training of paretic hand. During "PNS+AOsham+Training" session, PNS was given as described before. During the last 30 minutes of the PNS, subjects were shown different photos illustrating a letter, a number or a hand as AOsham. The protocol of motor training was the same as described before. In the session of "PNSsham+AOsham+Training", The 1-hour PNSsham was conducted with the electrical stimulation unit turned on but without current output. The protocols for AOsham and motor training were the same as those described before.