Topography of cortical activation differs for fundamental and harmonic frequencies of the steady-state visual-evoked responses.: An EEG and PET H215O study
Topography of cortical activation differs for fundamental and harmonic frequencies of the steady-state visual-evoked responses.: An EEG and PET H215O study
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DOI：
10.1093/cercor/bhl098
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发表时间：
2007-08-01
期刊：
影响因子：
3.7
通讯作者：
Masdeu, J. C.
中科院分区：
文献类型：
--
作者：
Pastor, M. A.;Valencia, M.;Masdeu, J. C.
在人类中，频率分级的视觉闪烁刺激(2-90赫兹)会引发脑电(EEG)稳态视觉诱发反应(SSVER)，其基频与刺激相同，此外还会产生一系列谐波反应。SSVER的基本成分是由初级视觉皮质(V1)突触活动增加所产生的。我们着手确定人类的谐波反应起源于大脑皮层。为此，我们记录了5个不同频率(5、10、15、25和40赫兹)的SSVERs，并在相同频率的视觉刺激下用正电子发射断层扫描-(H2O)-O-15测量局部脑血流量(RCBF)。以SSVERs一次谐波的幅度加权的rCBF对比显示，垂直于V1的皮质条带被激活，包括大部分顶枕沟的下半部。这一区域与由基频激活的初级视觉皮质的重叠最小。另一种方法，用低分辨率大脑电磁断层成像估计脑电皮质源电流密度，得出了同样的结果。我们的发现表明，顶枕沟的下侧部分含有联合视觉皮质，参与了刺激的处理，这可以像闪烁的光源一样简单。
In humans, visual flicker stimuli of graded frequency (2-90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-(H2O)-O-15 at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parietooccipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with low-resolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the processing of stimuli that can be as simple as a flickering light source.