CORTICAL GENERATORS OF THE CI COMPONENT OF THE PATTERN-ONSET VISUAL EVOKED-POTENTIAL
CORTICAL GENERATORS OF THE CI COMPONENT OF THE PATTERN-ONSET VISUAL EVOKED-POTENTIAL
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DOI：
10.1016/0168-5597(87)90046-3
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发表时间：
1987-07-01
期刊：
影响因子：
--
通讯作者：
SMITH, KRH
中科院分区：
文献类型：
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作者：
BUTLER, SR;GEORGIOU, GA;SMITH, KRH
记录到模式发作的13个通道的视觉诱发电位(VEP)，仅限于周边视野的单个八分象限、中心凹的一半和象限。在每个通道中测量CI分量的电压，以定义每个受刺激扇区的地形。然后对获得的电位场进行分析，以找出在头皮上产生相应电压模式的偶极的方向和位置。计算的偶极子的位置与CI产生于纹状皮质的假设一致。计算的位置和方向与纹外皮质中来源的其他布置不兼容。一个重大问题依然存在。如果CI确实是由纹状皮质产生的，那么刺激外周场所激发的偶极子的方向表明，皮层是表面负的。这导致了一种预测，即黄斑中心凹刺激将引起CI，而在后电极为负。本文报道的实验证实，CI在这样的刺激下是正的，其来源被计算为水平偶极子，其正极子向后定向。黄斑中心凹CI的极性反转有两种可能的解释：(A)与刺激中心凹相关的宏观电位与刺激周围野相关的宏观电位的极性相反；(B)视网膜定位图的中心凹区域延伸到外侧距裂隙，其大部分面向极部皮质的相反方向。
Thirteen-channel visual evoked potentials (VEPs) to pattern-onset were recorded with stimuli restricted to individual octants of the peripheral field, to halves and to quadrants of the fovea. The voltage of the CI component was measured in each channel to define its topography for each stimulated sector. The potential fields so obtained were then analysed to find the orientation and location of a dipole that would produce a corresponding pattern of voltages at the scalp. The locations of the computed dipoles are consistent with the hypothesis that CI is generated in striate cortex. The computed locations and orientations are not compatible with alternative arrangements of sources in extrastriate cortex. A significant problem remains. If CI is indeed generated by the striate cortex then the orientation of the dipoles excited by stimulation of the peripheral field indicates that the cortex is surface negative. This leads to the prediction that foveal stimuli will elicit a CI which is negative at posterior electrodes. The experiments reported here confirm that CI is positive with such stimuli, and its source is calculated as a horizontal dipole with its positive pole oriented posterolaterally. Two possible explanations are considered for the reversed polarity of foveal CI: (a) that macropotentials associated with stimulation of the fovea are opposite in polarity from those associated with stimulation of the peripheral field; (b) that the foveal area of the retinotopic map extends into the lateral calcarine fissure with the effect the much of it faces in the reverse direction from the cortex at the pole.