title: Changes in somatosensory-evoked potentials and high-frequency oscillations after paired-associative stimulation.
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 (PAS(25)) and 10 ms (PAS(10)). 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. PAS(25) 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 PAS(10) 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. PAS(25/10) over the somatosensory cortex did not affect SEPs and HFOs. PAS(25/10) 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.
authors.affiliation: Department of Neurology, Institute of Neurological Sciences, Faculty of Medicine, Tottori University, 36-1 Nishicho, Yonago, 683-8504, Japan. takebou@grape.med.tottori-u.ac.jp
authors.forename: Takenobu
authors.initials: T
authors.lastname: Murakami
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakuma
authors.forename: Takashi
authors.initials: T
authors.lastname: Nomura
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Uemura
authors.forename: Isao
authors.initials: I
authors.lastname: Hashimoto
authors.forename: Kenji
authors.initials: K
authors.lastname: Nakashima
mesh_terms: D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D001683:Biological Clocks / Q000502:physiology*; D004558:Electric Stimulation; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007395:Interneurons / Q000502:physiology; D008297:Male; D008475:Median Nerve / Q000502:physiology; D009044:Motor Cortex / Q000033:anatomy & histology / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology; D009434:Neural Pathways / Q000033:anatomy & histology / Q000502:physiology; D009473:Neuronal Plasticity / Q000502:physiology; D017966:Pyramidal Cells / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D013003:Somatosensory Cortex / Q000033:anatomy & histology / Q000502:physiology*; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D005680:gamma-Aminobutyric Acid