Experimental Brain Research

, Volume 184, Issue 3, pp 339–347

Changes in somatosensory-evoked potentials and high-frequency oscillations after paired-associative stimulation

Authors

    • Department of Neurology, Institute of Neurological Sciences, Faculty of MedicineTottori University
  • Kenji Sakuma
    • Department of Neurology, Institute of Neurological Sciences, Faculty of MedicineTottori University
  • Takashi Nomura
    • Department of Neurology, Institute of Neurological Sciences, Faculty of MedicineTottori University
  • Yusuke Uemura
    • Department of Neurology, Institute of Neurological Sciences, Faculty of MedicineTottori University
  • Isao Hashimoto
    • Kanazawa Institute of Technology
  • Kenji Nakashima
    • Department of Neurology, Institute of Neurological Sciences, Faculty of MedicineTottori University
Research Article

DOI: 10.1007/s00221-007-1103-0

Cite this article as:
Murakami, T., Sakuma, K., Nomura, T. et al. Exp Brain Res (2008) 184: 339. doi:10.1007/s00221-007-1103-0

Abstract

Paired-associative stimulation (PAS), combining electrical median nerve stimulation with transcranial magnetic stimulation (TMS) with a variable delay, causes long-term potentiation or depression (LTP/LTD)-like cortical plasticity. In the present study, we examined how PAS over the motor cortex affected a distant site, the somatosensory cortex. Furthermore, the influences of PAS on high-frequency oscillations (HFOs) were investigated to clarify the origin of HFOs. Interstimulus intervals between median nerve stimulation and TMS were 25 ms (PAS25) and 10 ms (PAS10). PAS was performed over the motor and somatosensory cortices. SEPs following median nerve stimulation were recorded before and after PAS. HFOs were isolated by 400–800 Hz band-pass filtering. PAS25 over the motor cortex increased the N20–P25 and P25–N33 amplitudes and the HFOs significantly. The enhancement of the P25–N33 amplitude and the late HFOs lasted more than 60 min. After PAS10 over the motor cortex, the N20–P25 and P25–N33 amplitudes decreased for 40 min, and the HFOs decreased for 60 min. Frontal SEPs were not affected after PAS over the motor cortex. PAS25/10 over the somatosensory cortex did not affect SEPs and HFOs. PAS25/10 over the motor cortex caused the LTP/LTD-like phenomena in a distant site, the somatosensory cortex. The PAS paradigms over the motor cortex can modify both the neural generators of SEPs and HFOs. HFOs may reflect the activation of GABAergic inhibitory interneurons regulating pyramidal neurons in the somatosensory cortex.

Keywords

Somatosensory-evoked potentials (SEPs)High-frequency oscillations (HFOs)Paired-associative stimulation (PAS)Somatosensory cortexPlasticity

Copyright information

© Springer-Verlag 2007