Analysis of spatial patterns of phase in neocortical gamma EEGs in rabbit
Analysis of spatial patterns of phase in neocortical gamma EEGs in rabbit
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DOI：
10.1152/jn.2000.84.3.1266
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发表时间：
2000-09-01
影响因子：
2.5
通讯作者：
Barrie, JM
中科院分区：
文献类型：
--
作者：
Freeman, WJ;Barrie, JM
将64个电极（8 × 8，7 × 7 mm）的阵列植入训练辨别相应模态的条件刺激的兔子的视觉、听觉或躯体感觉皮层的表面上。64个脑电图（EEG）轨迹在任何时候都显示出高度的波形空间相干性，最大主成分分析成分的方差平均>90%。用快速傅立叶变换（FFT）对EEG信号进行分解，得到128 ms内的幅度调制和相位调制（AM和PM）空间分布。空间（2维）和时间（1维）过滤器的设计，以优化分类的空间AM模式在伽马范围（20-80 Hz）相对于歧视性条件刺激。没有证据表明刺激依赖的分类的空间PM模式。相反，一些空间PM分布符合圆锥形的模式。圆锥顶点的位置和标志（最大超前或滞后）随每次复发而随机变化。相位梯度的斜率在对应于轴突平行于皮质表面延伸的传导速度的范围内变化。相锥的持续时间和复发时间对应于最佳分类的空间AM模式。的解释是先进的相锥的状态转换的表现形式，在介观动态的感觉皮层的间歇性AM模式的形成。相位锥显示伽马EEG空间相干性不是由于单个深置偶极发生器的体积传导，也不是由于单极记录上参考导联部位的活动。顶端符号的随机变化表明，伽马AM模式是自组织的，并没有施加丘脑起搏器。半功率半径的相位梯度提供了一个有用的措施的软边界条件的形成和读出的合作皮层域负责绑定感官信息到上下文中的感知过程中的先前经验。
Arrays of 64 electrodes (8 X 8, 7 X 7 mm) were implanted epidurally on the surface of the visual, auditory or somatosensory cortex of rabbits trained to discriminate conditioned stimuli in the corresponding modality. The 64 electroencephalographic (EEG) traces at all times displayed a high degree of spatial coherence in wave form, averaging >90% of the variance in the largest principal components analysis component. The EEGs were decomposed with the fast Fourier transform (FFT) to give the spatial distributions of amplitude and phase modulation (AM and PM) in segments 128 ms in duration. Spatial (2-dimensional) and temporal (1-dimensional) filters were designed to optimize classification of the spatial AM patterns in the gamma range (20-80 Hz) with respect to discriminative conditioned stimuli. No evidence was found for stimulus-dependent classification of the spatial PM patterns. Instead some spatial PM distributions conformed to the pattern of a cone. The location and sign (maximal lead or lag) of the conic apex varied randomly with each recurrence. The slope of the phase gradient varied in a range corresponding to that of the conduction velocities reported of axons to extend parallel to the cortical surfaces. The durations and times of recurrence of the phase cones corresponded to those of the optimally classified spatial AM patterns. The interpretation is advanced that the phase cones are manifestations of state transitions in the mesoscopic dynamics of sensory cortices by which the intermittent AM patterns are formed. The phase cones show that the gamma EEG spatial coherence is not due to volume conduction from a single deep-lying dipole generator nor to activity at the site of the reference lead on monopolar recording. The random variation of the apical sign shows that gamma AM patterns are self-organized and are not imposed by thalamic pacemakers. The half-power radius of the phase gradient provides a useful measure of the soft boundary condition for the formation and read-out of cooperative cortical domains responsible for binding sensory information into the context of prior experience in the process of perception.