Focal reduction of intracortical inhibition in the motor cortex by selective proprioceptive stimulation |
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Authors: | Email author" target="_blank">Karin?RosenkranzEmail author Alessandra?Pesenti Walter?Paulus Frithjof?Tergau |
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Institution: | Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, Queen Square 8-11, London, WC1N 3BG, UK. k.rosenkranz@ion.ucl.ac.uk |
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Abstract: | The influence of proprioception on motorcortical excitability was assessed by muscle vibration (MV; 80 Hz, 0.5 mm amplitude)
of the flexor carpi radialis muscle (FCR) and compared to voluntary contraction and relaxation conditions. Motor thresholds,
motor-evoked potentials (MEPs) in response to single pulses of transcranial magnetic stimulation (TMS) and the intracortical
inhibition (ICI) and facilitation (ICF) after paired magnetic stimuli were studied. A control experiment using TMS inducing
posteriorly directed current was performed. MEPs were recorded simultaneously from the FCR, the extensor carpi radialis, the
abductor pollicis brevis and the first dorsal interosseus. In the FCR, MV led to an increase of excitability shown by a decrease
of motor threshold, a facilitation of MEPs in response to single-pulse TMS, a reduction of ICI and an increase of ICF. Since
especially the ICI and ICF remain unchanged in other recorded muscles, this increase of excitability is specific for the vibrated
muscle. With posteriorly directed current the ICI in the FCR was reduced as well, showing an involvement of later I-waves.
We suggest that MV induces a focused motorcortical activation which relies on a reduced activity of intracortical inhibitory
interneuronal circuits targeting selectively the motorcortical representation of the vibrated muscle.
Electronic Publication |
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Keywords: | Muscle vibration Intracortical excitability Focused motorcortical activation Transcranial magnetic stimulation Human |
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