title: Motor training and the combination of action observation and peripheral nerve stimulation reciprocally interfere with the plastic changes induced in primary motor cortex excitability.
abstract: AO-PNS is a stimulation protocol combining action observation (AO) and peripheral nerve stimulation (PNS) to induce plasticity in the primary motor cortex (M1) (increased excitability). Another method to increase M1 excitability is motor training. The combination of two protocols, which individually induce long-term potentiation (LTP)-like plasticity in overlapping neural circuits, results in a transitory occlusion or reverse of this phenomenon. This study aimed to understand the neurophysiological mechanisms underlying AO-PNS by testing whether AO-PNS and motor training induced LTP-like plasticity in, at least partially, overlapping neural networks. One group of participants practiced a motor training (finger opposition movements) followed by AO-PNS, whereas another group performed the two protocols in reverse order. Motor performance was evaluated by means of a sensor-engineered glove and transcranial magnetic stimulation was used to assess M1 excitability before and after each conditioning protocol. Motor training increased movement frequency, suggesting the occurrence of motor learning in both groups. When applied on first, both motor training and AO-PNS significantly increased the motor-evoked potential (MEP), but occluded the increase of cortical excitability expected after the following protocol, leading to a significant decrease of MEP amplitude. These results suggest that motor training and AO-PNS act on partially overlapping neuronal networks, which include M1, and that AO-PNS might be able to induce LTP-like plasticity in a similar way to overt movement execution. This candidates AO-PNS as methodology potentially useful when planning rehabilitative interventions on patients who cannot voluntarily move.
authors.affiliation: Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy.
authors.forename: Ambra
authors.initials: A
authors.lastname: Bisio
authors.affiliation: Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Avanzino
authors.affiliation: Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Biggio
authors.affiliation: Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy.
authors.forename: Piero
authors.initials: P
authors.lastname: Ruggeri
authors.affiliation: Department of Experimental Medicine, Section of Human Physiology, University of Genoa, 16132 Genoa, Italy. Electronic address: marco.bove@unige.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Bove
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000502:physiology; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000502:physiology*; D009473:Neuronal Plasticity / Q000502:physiology*; D010525:Peripheral Nerves / Q000502:physiology*; D011214:Practice, Psychological; D011597:Psychomotor Performance / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult
keywords: action observation; associative plasticity; long-term potentiation; motor training; peripheral nerve electrical stimulation; transcranial magnetic stimulation