Fukuda Miho, Nishida Masaaki, Juhász Csaba, Muzik Otto, Sood Sandeep, Chugani Harry T, Asano Eishi
Department of Pediatrics, Wayne State University, Detroit Medical Center, Detroit, MI, 48201, USA.
Brain. 2008 Jul;131(Pt 7):1793-805. doi: 10.1093/brain/awn100. Epub 2008 May 27.
Recent studies have suggested that cortical gamma-oscillations are tightly linked with various forms of physiological activity. In the present study, the dynamic changes of intracranially recorded median-nerve somatosensory-evoked potentials (SEPs) and somatosensory-induced gamma-oscillations were animated on a three-dimensional MR image, and the temporal and spatial characteristics of these activities were analysed in 10 children being evaluated for epilepsy surgery. Visual and quantitative assessments revealed that short-latency SEPs and somatosensory-induced gamma-oscillations predominantly involved the post-central gyrus and less intensely involved the pre-central gyrus and the anterior parietal lobule. Formation of a dipole of N20 peak with opposite polarities across the central sulcus was well delineated in animation movies. High-frequency (100-250 Hz) somatosensory-induced gamma-oscillations emerged in the post-central gyrus at 13.6-17.5 ms after median-nerve stimulation, gradually slowed down in frequency around and below 100 Hz, and progressively involved the neighbouring areas. A substantial proportion of somatosensory-induced gamma-oscillations was initially phase-locked and the proportion of a non-phase-locked component gradually increased over time. The primary motor hand areas proven by cortical stimulation frequently coincided with the sites showing the largest N20 peak and the largest somatosensory-induced gamma oscillations. In vivo animation of SEPs and somatosensory-induced gamma oscillations both may be utilized to localize the primary sensory-motor hand area in pre-surgical evaluation. The dipole on SEPs is consistent with the previously accepted notion that the cortices along the central sulcus are activated. The high-frequency somatosensory-induced gamma-oscillations in the post-central gyrus may represent the initial neural processing for external somatosensory stimuli, whereas the subsequent lower-frequency oscillations might represent the reafferent cortical activity occurring in larger cortical networks.
近期研究表明，皮层γ振荡与多种形式的生理活动紧密相关。在本研究中，将颅内记录的正中神经体感诱发电位（SEP）和体感诱发γ振荡的动态变化在三维磁共振图像上进行了动态显示，并对10名接受癫痫手术评估的儿童的这些活动的时间和空间特征进行了分析。视觉和定量评估显示，短潜伏期SEP和体感诱发γ振荡主要累及中央后回，对中央前回和顶叶前小叶的累及程度较轻。在动画电影中清晰地描绘出了中央沟两侧具有相反极性的N20峰偶极子的形成。高频（100 - 250Hz）体感诱发γ振荡在正中神经刺激后13.6 - 17.5ms出现在中央后回，频率在100Hz及以下逐渐减慢，并逐渐累及邻近区域。相当一部分体感诱发γ振荡最初是锁相的，非锁相成分的比例随时间逐渐增加。经皮层刺激证实的主要运动手区经常与显示最大N20峰和最大体感诱发γ振荡的部位重合。SEP和体感诱发γ振荡的体内动态显示均可用于术前评估中定位主要感觉运动手区。SEP上的偶极子与先前公认的中央沟沿线皮层被激活的观点一致。中央后回中高频体感诱发γ振荡可能代表对外界体感刺激的初始神经处理，而随后较低频率的振荡可能代表在更大皮层网络中发生的再传入皮层活动。
