Multipulse transcranial magnetic stimulation of human motor cortex produces short-latency corticomotor facilitation via two distinct mechanisms
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Multipulse transcranial magnetic stimulation of human motor cortex produces short-latency corticomotor facilitation via two distinct mechanisms. / Kesselheim, Janine; Takemi, Mitsuaki; Christiansen, Lasse; Karabanov, Anke Ninija; Siebner, Hartwig Roman.
In: Journal of Neurophysiology, Vol. 129, No. 2, 2023, p. 410-420.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Multipulse transcranial magnetic stimulation of human motor cortex produces short-latency corticomotor facilitation via two distinct mechanisms
AU - Kesselheim, Janine
AU - Takemi, Mitsuaki
AU - Christiansen, Lasse
AU - Karabanov, Anke Ninija
AU - Siebner, Hartwig Roman
N1 - CURIS 2023 NEXS 046
PY - 2023
Y1 - 2023
N2 - Single-pulse transcranial magnetic stimulation (TMS) of the precentral hand representation (M1HAND) can elicit indirect waves in the corticospinal tract at a periodicity of ∼660 Hz, called I-waves. These descending volleys are produced by transsynaptic excitation of fast-conducting corticospinal axons in M1HAND. Paired-pulse TMS can induce short-interval intracortical facilitation (SICF) of motor evoked potentials (MEPs) at interpulse intervals that match I-wave periodicity. This study examined whether short-latency corticospinal facilitation engages additional mechanisms independently of I-wave periodicity. In 19 volunteers, one to four biphasic TMS pulses were applied to left M1HAND with interpulse intervals adjusted to the first peak or trough of the individual SICF curve at different intensities to probe the intensity-response relationship. Multipulse TMSHAND at individual peak latency facilitated MEP amplitudes and reduced resting motor threshold (RMT) compared with single pulses. Multipulse TMSHAND at individual trough latency also produced a consistent facilitation of MEPs and a reduction of RMT. Short-latency facilitation at trough latency was less pronounced, but the relative difference in facilitation decreased with increasing stimulus intensity. Increasing the pulse number had only a modest effect. Two mechanisms underlie short-latency facilitation caused by biphasic multipulse TMSHAND. One intracortical mechanism is related to I-wave periodicity and engages fast-conducting direct projections to spinal motoneurons. A second corticospinal mechanism does not rely on I-wave rhythmicity and may be mediated by slower-conducting indirect pyramidal tract projections from M1HAND to spinal interneurons. The latter mechanism deserves more attention in studies of the corticomotor system and its link to manual motor control using the MEP.
AB - Single-pulse transcranial magnetic stimulation (TMS) of the precentral hand representation (M1HAND) can elicit indirect waves in the corticospinal tract at a periodicity of ∼660 Hz, called I-waves. These descending volleys are produced by transsynaptic excitation of fast-conducting corticospinal axons in M1HAND. Paired-pulse TMS can induce short-interval intracortical facilitation (SICF) of motor evoked potentials (MEPs) at interpulse intervals that match I-wave periodicity. This study examined whether short-latency corticospinal facilitation engages additional mechanisms independently of I-wave periodicity. In 19 volunteers, one to four biphasic TMS pulses were applied to left M1HAND with interpulse intervals adjusted to the first peak or trough of the individual SICF curve at different intensities to probe the intensity-response relationship. Multipulse TMSHAND at individual peak latency facilitated MEP amplitudes and reduced resting motor threshold (RMT) compared with single pulses. Multipulse TMSHAND at individual trough latency also produced a consistent facilitation of MEPs and a reduction of RMT. Short-latency facilitation at trough latency was less pronounced, but the relative difference in facilitation decreased with increasing stimulus intensity. Increasing the pulse number had only a modest effect. Two mechanisms underlie short-latency facilitation caused by biphasic multipulse TMSHAND. One intracortical mechanism is related to I-wave periodicity and engages fast-conducting direct projections to spinal motoneurons. A second corticospinal mechanism does not rely on I-wave rhythmicity and may be mediated by slower-conducting indirect pyramidal tract projections from M1HAND to spinal interneurons. The latter mechanism deserves more attention in studies of the corticomotor system and its link to manual motor control using the MEP.
KW - Faculty of Science
KW - Transcranial magnetic stimulation
KW - Motor cortex
KW - Short latency intracortical facilitation
KW - I-waves
U2 - 10.1152/jn.00263.2022
DO - 10.1152/jn.00263.2022
M3 - Journal article
C2 - 36629338
VL - 129
SP - 410
EP - 420
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
SN - 0022-3077
IS - 2
ER -
ID: 333034927