Verkindt C, Bertrand O, Perrin F, Echallier J F, Pernier J
Brain Signals and Processes Laboratory, INSERM, Unité 280, Lyon, France.
Electroencephalogr Clin Neurophysiol. 1995 Mar;96(2):143-56. doi: 10.1016/0168-5597(94)00242-7.
The tonotopic organization of the human auditory cortex has been investigated by means of scalp potential mapping and dipole modelling of the evoked response occurring around 100 msec after the stimulus onset. The major characteristics of the topographical changes observed with increasing stimulus frequency were statistically demonstrated. Using a 3-concentric sphere head model, the scalp potential distributions can be explained in first approximation by two equivalent current dipoles, located in the supratemporal plane and mimicking the activity of both auditory cortices. To take into account the temporal aspects of the brain activities, 3 time-varying dipole strategies were tested. Frequency dependence of the dipole orientation has been evidenced in both hemispheres with the 3 models, whereas no significant change in dipole position was found. The tilt in dipole orientation could be related to the folding geometry of Heschl's gyrus, which varies with depth. In agreement with previous MEG findings, this brings new evidence for a tonotopic organization of the auditory cortical area involved in the N100 wave generation. Moreover, distinct frequency dependences of the equivalent current dipoles were observed in the early and the late parts of the N100. This study demonstrates that simple dipolar models, applied on electrical data, make it possible to reveal functionally distinct cortical areas.
通过头皮电位映射和对刺激开始后约100毫秒出现的诱发反应进行偶极子建模，对人类听觉皮层的音频拓扑组织进行了研究。随着刺激频率增加所观察到的地形变化的主要特征得到了统计学证明。使用一个三同心球头部模型，头皮电位分布可以初步用位于颞上平面的两个等效电流偶极子来解释，这两个偶极子模拟了两个听觉皮层的活动。为了考虑大脑活动的时间方面，测试了三种随时间变化的偶极子策略。三种模型均已证明两个半球中偶极子方向存在频率依赖性，而偶极子位置未发现显著变化。偶极子方向的倾斜可能与颞横回的折叠几何形状有关，其随深度而变化。与先前的脑磁图研究结果一致，这为参与N100波产生的听觉皮层区域的音频拓扑组织提供了新证据。此外，在N100的早期和晚期观察到等效电流偶极子有不同的频率依赖性。这项研究表明，应用于电数据的简单偶极子模型能够揭示功能上不同的皮层区域。
