Journal Article

FZJ-2015-05244

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png What Makes the Muscle Twitch: Motor System Connectivity and TMS-Induced Activity

Volz, L. J. ; Hamada, M. ; Rothwell, J. C. ; Grefkes, C. (Corresponding author)FZJ*

2015
Oxford Univ. Press Oxford

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Please use a persistent id in citations: doi:10.1093/cercor/bhu032

Abstract: Transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) evokes several volleys of corticospinal activity. While the earliest wave (D-wave) originates from axonal activation of cortico-spinal neurons (CSN), later waves (I-waves) result from activation of mono- and polysynaptic inputs to CSNs. Different coil orientations preferentially stimulate cortical elements evoking different outputs: latero-medial-induced current (LM) elicits D-waves and short-latency electromyographic responses (MEPs); posterior–anterior current (PA) evokes early I-waves. Anterior–posterior current (AP) is more variable and tends to recruit later I-waves, featuring longer onset latencies compared with PA-TMS. We tested whether the variability in response to AP-TMS was related to functional connectivity of the stimulated M1 in 20 right-handed healthy subjects who underwent functional magnetic resonance imaging while performing an isometric contraction task. The MEP-latency after AP-TMS (relative to LM-TMS) was strongly correlated with functional connectivity between the stimulated M1 and a network involving cortical premotor areas. This indicates that stronger premotor–M1 connectivity increases the probability that AP-TMS recruits shorter latency input to CSNs. In conclusion, our data strongly support the hypothesis that TMS of M1 activates distinct neuronal pathways depending on the orientation of the stimulation coil. Particularly, AP currents seem to recruit short latency cortico-cortical projections from premotor areas.

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Contributing Institute(s):

1. Kognitive Neurowissenschaften (INM-3)

Research Program(s):

1. 572 - (Dys-)function and Plasticity (POF3-572) (POF3-572)

Appears in the scientific report 2015

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Database coverage:
; BIOSIS Previews ; Current Contents - Life Sciences ; IF >= 5 ; JCR ; NCBI Molecular Biology Database ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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