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Human Higher Brain Functions

開催日 2014/9/13
時間 15:00 - 16:00
会場 Room H(304)
Chairperson(s) 有光 威志 / Takeshi Arimitsu (慶應義塾大学医学部小児科学教室 / Department of Pediatrics, School of Medicine, Keio University, Japan)
小西 清貴 / Seiki Konishi (順天堂大学 医学部 生理学講座 / Department of Physiology, Juntendo University School of Medecine, Japan)

Functional connectivity from the human entorhinal cortex: a cortico-cortical evoked potential study

  • O3-H-3-2
  • 武山 博文 / Hirofumi Takeyama:1 松本 理器 / Riki Matsumoto:2 小林 勝哉 / Katsuya Kobayashi:1 宇佐美 清英 / Kiyohide Usami:1 下竹 昭寛 / Akihiro Shimotake:1 菊池 隆幸 / Takayuki Kikuchi:3 國枝 武治 / Takeharu Kunieda:3 宮本 享 / Susumu Miyamoto:3 高橋 良輔 / Ryosuke Takahashi:1 池田 昭夫 / Akio Ikeda:2 
  • 1:京都大院・医・脳病態生理 / Dept Neurol, Univ of Kyoto, Kyoto, Japan 2:京都大院・医・てんかん・運動異常生理学講座 / Dept Epilepsy, Movement Disorders and Physiology, Univ of Kyoto, Kyoto, Japan 3:京都大院・医・脳神経外科 / Dept Neurosurgery, Univ of Kyoto, Kyoto, Japan 

Background: Entorhinal cortex (EC), the important subregion in the medial temporal lobe memory network, has been considered to have rich connections to various cortical regions, but little is known in humans. We aimed to clarify its connectivity by means of an electrical, tract tracing method of cortico-cortical evoked potential (CCEP) (Matsumoto et al., 2004).
Methods: We recruited 7 patients with medically intractable temporal lobe epilepsy, who underwent invasive presurgical evaluations with subdural electrodes (3 men, age 17-52, 56-102 electrodes). Single-pulse electrical stimulation was delivered to a pair of electrodes on EC and that 2 cm lateral to EC (non-EC: mainly on the anterior fusiform gyrus). Evoked responses time-locked to stimuli (CCEPs) were recorded from the rest of the cortices covered by subdural electrodes.
Results: In all 7 patients, EC stimulation evoked early positive potentials of similar waveform and latency within the subjects across almost all electrodes [Latency of the positive potential: average across electrodes within the subjects, mean 17.5 ms (range 9.5-34.9 ms), SD within the subjects, mean 3.1 ms (range 0.8-9.8 ms)]. This sharp positive potential was generally followed by a blunted, rather sustained negative potential. In contrast, in non-EC stimulation, the positive potential of longer latency was observed at significantly fewer electrodes than in EC stimulation (p<0.05, Wilcoxon ranking scale test). Remote isolated CCEP fields, which usually reflect direct cortico-cortical connections, were significantly fewer in EC stimulation than in non-EC stimulation (p<0.05, Wilcoxon ranking scale test).
Discussion: In the present CCEP study, uniform sharply contoured positive potentials were broadly recorded from various cortical regions. This far field potential like responses may indicate that EC has rich connections to various cortical regions probably through subcortical structures such as thalamus, or that EC stimulation simply induced widely distributed electric field due to volume conduction.

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