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Brain oscillations in its physiology and pathophysiology

開催日 2014/9/11
時間 9:00 - 11:00
会場 Room C(502)
Chairperson(s) 池田 昭夫 / Akio Ikeda (京都大学大学院医学研究科 てんかん・運動異常生理学講座 / Department of Epilepsy, Movement Disorders and Physiology, Kyoto University Graduate School of Medicine, Japan)
美馬 達哉 / Tatsuya Mima (京都大学大学院医学研究科附属脳機能総合研究センター / Human Brain Research Center, Kyoto University Graduate School of Medicine, Japan)

Spontaneous and induced neural oscillations in human epilepsy

  • S1-C-1-5
  • 松本 理器 / Riki Matsumoto:1 國枝 武治 / Takeharu Kunieda:2 池田 昭夫 / Akio Ikeda:1 
  • 1:京都大学・医・てんかん・運動異常生理学 / Dept Epilepsy, Mov Disord and Physiol, Kyoto Univ Grad Sch Med, Japan 2:京都大学・医・脳神経外科 / Dept Neurosurg, Kyoto Univ Grad Sch Med, Japan 

Advancement of wide-band electrocorticographic (ECoG) recording has recently enabled us to investigate neural oscillations ranging from ultra-slow to high gamma activities in patients with partial epilepsy who underwent presurgical invasive evaluation with subdural electrodes. We have shown that during seizures both ultra-slow (ictal slow shift) and high-gamma oscillation (HFO) occurred at the epileptic focus in a more localized fashion, compared with conventional EEG findings. The behaviors of ictal ultra-slow and high-gamma activities were different, indicating different generator mechanisms.
Recently, the data have been accumulated that the high frequency oscillations/activities (>80 Hz) recorded with the macroelectrodes are proxies for neuronal activities or spiking synchrony. HFOs induced by various cognitive/motor tasks ('cognitive' HFOs) ranged between 80-200 Hz, while those related with epileptogenicity (interictal epileptic HFOs) ranged not only in the same range (80-250 Hz, ripple) but also in higher frequencies (>250 Hz, fast ripples).
We are currently investigating HFOs induced by single-pulse (1 Hz) electrical stimulation (stimulus-induced HFOs) to probe neuronal properties to the exogenous (electrical) inputs. The epileptic focus showed higher HFO power in the ripple and fast ripple range compared with the control cortex. Investigation of the control normal cortices during non-REM sleep revealed that transient HFO power increase, namely, increased neuronal excitability was followed by intense decrease or inhibition across the lobes. It was only the frontal lobe that showed a rebounded activity or a hyper-synchronized overshoot after the intense inhibition. This likely constitutes the physiological basis of the nocturnal seizures during NREM sleep in frontal lobe epilepsy.

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