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Multimodal output mapping of human central motor representation on different spatial scales
Author(s) -
Classen Joseph,
Knorr Uwe,
Werhahn Konrad J.,
Schlaug Gottfried,
Kunesch Erwin,
Cohen Leonardo G.,
Seitz Rüdiger J.,
Benecke Reiner
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.163bf.x
Subject(s) - transcranial magnetic stimulation , cog , precentral gyrus , neuroscience , primary motor cortex , motor cortex , human brain , forearm , brain mapping , cerebral cortex , positron emission tomography , functional magnetic resonance imaging , anatomy , psychology , magnetic resonance imaging , physics , stimulation , medicine , computer science , artificial intelligence , radiology
1 Non‐invasive mapping by focal transcranial magnetic stimulation (TMS) is frequently used to investigate cortical motor function in the intact and injured human brain. We examined how TMS‐derived maps relate to the underlying cortical anatomy and to cortical maps generated by functional imaging studies. 2 The centres of gravity (COGs) of TMS maps of the first dorsal intersosseus muscle (FDI) were integrated into 3‐D magnetic resonance imaging (MRI) data sets in eleven subjects. In seven of these subjects the TMS‐derived COGs were compared with the COG of regional cerebral blood flow increases using positron emission tomography (PET) in an index finger flexion protocol. 3 Mean TMS‐derived COG projections were located on the posterior lip of the precentral gyrus and TMS‐derived COG projections were in close proximity to the mean PET‐derived COG, suggesting that the two methods reflect activity of similar cortical elements. 4 Criteria for a reliable assessment of the COG and the number of positions with a minimum amplitude of two‐thirds of the maximum motor‐evoked potential (T3Ps) were determined as a function of the number of stimuli and extension of the stimulation field. COGs and T3Ps were compared with an estimate of the size of the human motor cortex targeting α‐motoneurons of forearm muscles. This comparison suggests that TMS can retrieve spatial information on cortical organization below the macroanatomic scale of cortical regions. 5 Finally, we studied the cortical representation of hand muscles in relation to facial and foot muscle representations and investigated hemispherical asymmetries. We did not find any evidence for a different ipsi‐ or contralateral representation of the mentalis muscle. Also, no difference was found between FDI representations on the dominant versus the non‐dominant hemisphere.