TY - JOUR
T1 - Hemispheric asymmetry and somatotopy of afferent inhibition in healthy humans
AU - Helmich, R. C.G.
AU - Bäumer, T.
AU - Siebner, H. R.
AU - Bloem, Bastiaan R.
AU - Münchau, A.
N1 - Funding Information:
Acknowledgements R.C.G. Helmich was sponsored by De Neder-landse Vereniging voor Dystonie Patiënten, De Hersenstichting Nederland, De Fundatie van de Vrijvrouwe van Renswoude and Stichting Nijmeegs Universiteits Fonds (SNUF). A. Münchau and H.R. Siebner were supported by the Volkswagenstiftung and A. Münchau also by the Forschungsförderungs-Fond of the Hamburg University Hospital. We wish to thank the reviewers of this paper for their thoughtful and constructive criticism. Experiment 2 was redesigned on the basis of their suggestions. We also thank Melanie Jonas for statistical advice.
PY - 2005/11
Y1 - 2005/11
N2 - A conditioning electrical stimulus to a digital nerve can inhibit the motor-evoked potentials (MEPs) in adjacent hand muscles elicited by transcranial magnetic stimulation (TMS) to the contralateral primary motor cortex (M1) when given 25-50 ms before the TMS pulse. This is referred to as short-latency afferent inhibition (SAI). We studied inter-hemispheric differences (Experiment 1) and within-limb somatotopy (Experiment 2) of SAI in healthy right-handers. In Experiment 1, conditioning electrical pulses were applied to the right or left index finger (D2) and MEPs were recorded from relaxed first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscles ipsilateral to the conditioning stimulus. We found that SAI was more pronounced in right hand muscles. In Experiment 2, electrical stimulation was applied to the right D2 and MEPs were recorded from ipsilateral FDI, extensor digitorum communis (EDC) and biceps brachii (BB) muscles. The amount of SAI did not differ between FDI, EDC and BB muscles. These data demonstrate inter-hemispheric differences in the processing of cutaneous input from the hand, with stronger SAI in the dominant left hemisphere. We also found that SAI occurred not only in hand muscles adjacent to electrical digital stimulation, but also in distant hand and forearm and also proximal arm muscles. This suggests that SAI induced by electrical D2 stimulation is not focal and somatotopically specific, but a more widespread inhibitory phenomenon.
AB - A conditioning electrical stimulus to a digital nerve can inhibit the motor-evoked potentials (MEPs) in adjacent hand muscles elicited by transcranial magnetic stimulation (TMS) to the contralateral primary motor cortex (M1) when given 25-50 ms before the TMS pulse. This is referred to as short-latency afferent inhibition (SAI). We studied inter-hemispheric differences (Experiment 1) and within-limb somatotopy (Experiment 2) of SAI in healthy right-handers. In Experiment 1, conditioning electrical pulses were applied to the right or left index finger (D2) and MEPs were recorded from relaxed first dorsal interosseus (FDI) and abductor digiti minimi (ADM) muscles ipsilateral to the conditioning stimulus. We found that SAI was more pronounced in right hand muscles. In Experiment 2, electrical stimulation was applied to the right D2 and MEPs were recorded from ipsilateral FDI, extensor digitorum communis (EDC) and biceps brachii (BB) muscles. The amount of SAI did not differ between FDI, EDC and BB muscles. These data demonstrate inter-hemispheric differences in the processing of cutaneous input from the hand, with stronger SAI in the dominant left hemisphere. We also found that SAI occurred not only in hand muscles adjacent to electrical digital stimulation, but also in distant hand and forearm and also proximal arm muscles. This suggests that SAI induced by electrical D2 stimulation is not focal and somatotopically specific, but a more widespread inhibitory phenomenon.
UR - http://www.scopus.com/inward/record.url?scp=28444479145&partnerID=8YFLogxK
U2 - 10.1007/s00221-005-0014-1
DO - 10.1007/s00221-005-0014-1
M3 - Journal articles
C2 - 16034577
AN - SCOPUS:28444479145
SN - 0014-4819
VL - 167
SP - 211
EP - 219
JO - Experimental Brain Research
JF - Experimental Brain Research
IS - 2
ER -
