Evidence of motor resonance in stroke patients with severe upper limb function impairments

Visuomotor paired associative stimulation enhances corticospinal excitability in post-stroke patients with upper-limb hemiparesis

We assess the effectiveness of a visuomotor paired associative stimulation (vm-PAS) protocol targeting the Action Observation Network (AON) in chronic post-stroke patients with upper-limb mild hemiparesis. Vm-PAS consisted of hand-grasping action observation stimuli repeatedly paired with transcranial magnetic stimulation (TMS) pulses over the ipsilesional primary motor cortex (M1). Fifteen post-stroke patients underwent a session of the vm-PAS and, as a control, of the standard excitatory PAS (M1-PAS), during which slow-rate electrical stimulation of the paretic limb was paired with M1-TMS. Before and after each PAS, we assessed corticospinal excitability (CSE), short-interval intracortical inhibition (SICI), and paretic wrist's voluntary movements. The two protocols induce distinct muscle-specific CSE enhancements: vm-PAS increases motor-evoked potentials (MEPs) recorded from the paretic first dorsal interosseous muscle. Conversely, M1-PAS increases MEPs recorded from the electrically stimulated extensor carpi radialis muscle. Vm-PAS efficacy correlates with hemiparesis chronicity: the higher the time elapsed since the stroke, the greater vm-PAS effects on CSE. Neither protocol affected SICI or wrist movements. Our results suggest that vm-PAS leads to muscle-specific enhancements of CSE in post-stroke patients, highlighting its potential for modulating M1 excitability after stroke. These findings show the efficacy of a cross-modal PAS protocol targeting the AON in an injured motor system.

The cerebellum and the Mirror Neuron System: A matter of inhibition? From neurophysiological evidence to neuromodulatory implications. A narrative review

Mirror neurons show activity during both the execution (AE) and observation of actions (AO). The Mirror Neuron System (MNS) could be involved during motor imagery (MI) as well. Extensive research suggests that the cerebellum is interconnected with the MNS and may be critically involved in its activities. We gathered evidence on the cerebellum's role in MNS functions, both theoretically and experimentally. Evidence shows that the cerebellum plays a major role during AO and MI and that its lesions impair MNS functions likely because, by modulating the activity of cortical inhibitory interneurons with mirror properties, the cerebellum may contribute to visuomotor matching, which is fundamental for shaping mirror properties. Indeed, the cerebellum may strengthen sensory-motor patterns that minimise the discrepancy between predicted and actual outcome, both during AE and AO. Furthermore, through its connections with the hippocampus, the cerebellum might be involved in internal simulations of motor programs during MI. Finally, as cerebellar neuromodulation might improve its impact on MNS activity, we explored its potential neurophysiological and neurorehabilitation implications.

Effectiveness of a Program Based on Action-Observation Training (AOT) on Motor, Functional and Cognitive Aspects in Patients with Cognitive Impairment: A Non-Randomized Controlled Trial

Cognitive impairment is frequent in elderly subjects. It is associated with motor impairment, a limitation in quality of life and frequently, institutionalization. The aim of this work is to test the efficacy of a therapeutic group program based on action-observation learning.

METHODS

a non-randomized controlled trial study was conducted. We included 40 patients with cognitive impairment from a nursing home who were categorized into mild and moderate cognitive impairment and divided separately into a control and experimental group. Experimental group performed a 4-week group work, in which each patient with mild cognitive impairment was paired with a patient with moderate cognitive impairment. Thus, patients with mild cognitive impairment observed a series of functional exercises performed by their peers and replicated them. Simultaneously, the patients with moderate cognitive impairment replicated the movement after observing it performed by a patient with mild cognitive impairment. The control group continued to receive their usual care at the center. The upper limb function, cognitive level and function in basic activities of human daily life were measured before and after the intervention and compared with the control group.

RESULTS

statistically significant differences were found in the functionality of basic activities of daily living, in the functionality of the upper limb and in the cognitive level in all patients in the experimental group regardless of the initial cognitive level. No statistically significant differences were found in the control group.

CONCLUSIONS

the implementation of a group, peer-based, action-observation learning therapeutic program is effective in improving the basic activities of human daily life, cognitive level and upper limb functionality in patients with mild and moderate dementia.