Action verb processing for exciting the motor cortex and promoting the recovery of upper limb function after stroke

Abstract

Objective To explore the effect of action verb processing on the excitability of the motor cortex and any effect on the upper limb motor function of stroke survivors. Methods Experiment 1: The motor evoked potential by transcranial magnetic stimulation (TMS-MEP) was measured while 18 healthy subjects were processing concrete action verbs or abstract verbs. Experiment 2: Eight hemiplegic stroke survivors were asked to read silently text describing concrete hand actions, and then repeat and explain the meaning of the action verbs used in the text. This was repeated for 30 minutes per day, 5 days per week for 3 weeks. In the 2nd week the same training was conducted except that the text was about abstract verbs. The modified Ashworth scale (MAS), Fugl-Meyer assessment (FMA), the Hong Kong version of the functional test for a hemiplegic upper extremity (FTHUE-HK) and a simple test for evaluating hand function (STEF) were used to assess upper limb motor function before and after the training each week. Results Experiment 1: Processing the concrete action verbs induced significantly greater MEP than processing the abstract verbs. Experiment 2: The average FMA and STEF ratings improved significantly after the training each week. Training with the concrete action verbs resulted in significantly better FMA and STEF scores than with the abstract verbs. The average MAS score increased significantly week by week. There was significantly more improvement in the average FTHUE-HK rating after the 1st and 3rd week of training than after the 2nd week. Conclusion Action verb processing induces greater motor cortex excitation than abstract verb processing among healthy subjects and better improves the upper limb motor function of stroke survivors. Key words: Embodied cognition; Action verb processing; Stroke; Hemiplegia; Transcranial magne-tic stimulation