TY - JOUR

T1 - Short-term adaptations in spinal cord circuits evoked by repetitive transcranial magnetic stimulation: possible underlying mechanisms

AU - Perez, Monica A.

AU - Lungholt, Bjarke K.S.

AU - Nielsen, Jens Bo

N1 - PUF 2005 5200 017

PY - 2005

Y1 - 2005

N2 - Repetitive transcranial magnetic stimulation (rTMS) has been shown to induce adaptations in cortical neuronal circuitries. In the present study we investigated whether rTMS, through its effect on corticospinal pathways, also produces adaptations at the spinal level, and what the neuronal mechanisms involved in such changes are. rTMS (15 trains of 20 pulses at 5 Hz) was applied over the leg motor cortical area in ten healthy human subjects. At rest motor evoked potentials (MEPs) in the soleus and tibialis anterior muscles were facilitated by rTMS (at 1.2×MEP threshold). In contrast, the soleus H-reflex was depressed for 1 s at stimulus intensities from 0.92 to 1.2×MEP threshold. rTMS increased the size of the long-latency depression of the soleus H-reflex evoked by common peroneal nerve stimulation and decreased the femoral nerve facilitation of the soleus H-reflex. These observations suggest that the depression of the H-reflex by rTMS can be explained, at least partly, by an increased presynaptic inhibition of soleus Ia afferents. In contrast, rTMS had no effect on disynaptic reciprocal Ia inhibition from ankle dorsiflexors to plantarflexors. We conclude that a train of rTMS may modulate transmission in specific spinal circuitries through changes in corticospinal drive. This may be of relevance for future therapeutic strategies in patients with spasticity.

AB - Repetitive transcranial magnetic stimulation (rTMS) has been shown to induce adaptations in cortical neuronal circuitries. In the present study we investigated whether rTMS, through its effect on corticospinal pathways, also produces adaptations at the spinal level, and what the neuronal mechanisms involved in such changes are. rTMS (15 trains of 20 pulses at 5 Hz) was applied over the leg motor cortical area in ten healthy human subjects. At rest motor evoked potentials (MEPs) in the soleus and tibialis anterior muscles were facilitated by rTMS (at 1.2×MEP threshold). In contrast, the soleus H-reflex was depressed for 1 s at stimulus intensities from 0.92 to 1.2×MEP threshold. rTMS increased the size of the long-latency depression of the soleus H-reflex evoked by common peroneal nerve stimulation and decreased the femoral nerve facilitation of the soleus H-reflex. These observations suggest that the depression of the H-reflex by rTMS can be explained, at least partly, by an increased presynaptic inhibition of soleus Ia afferents. In contrast, rTMS had no effect on disynaptic reciprocal Ia inhibition from ankle dorsiflexors to plantarflexors. We conclude that a train of rTMS may modulate transmission in specific spinal circuitries through changes in corticospinal drive. This may be of relevance for future therapeutic strategies in patients with spasticity.

U2 - 10.1007/s00221-004-2144-2

DO - 10.1007/s00221-004-2144-2

M3 - Journal article

VL - 162

SP - 202

EP - 212

JO - Experimental Brain Research

JF - Experimental Brain Research

SN - 0014-4819

IS - 2

ER -