Effects of Stimulus Size and Contrast on the Initial Primary Visual Cortical Response in Humans.
Effects of Stimulus Size and Contrast on the Initial Primary Visual Cortical Response in Humans.
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DOI：
10.1007/s10548-016-0530-2
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发表时间：
2017-07
期刊：
影响因子：
2.7
通讯作者：
Kelly SP
中科院分区：
文献类型：
--
作者：
Gebodh N;Vanegas MI;Kelly SP
几十年来对初级视觉皮层（V1）的颅内电生理学研究已经产生了许多关于大脑低级视觉回路中进行的计算的基本见解。一些最重要的工作已经简单地与神经反应的变化作为一个基本的刺激属性，如对比度和大小的函数的精确测量有关。令人惊讶的是，V1反应的这种简单但基本的表征尚未在人体电生理学中进行。在这里，我们报告这样一个详细的表征为初始的“C1”组成部分的头皮记录的视觉诱发电位（VEP）。已知C1主要由V1中的初始传入激活产生，但由于个体间解剖变异性而难以可靠地记录。我们使用模式脉冲多焦视觉诱发电位映射，以确定刺激位置，激活左下距状神经银行在每个人，然后测量强大的负C1后中线头皮光栅依次在该位置。我们发现，随着尺寸的增加以及对比度的增加，C1峰振幅明显和系统性增加，峰潜伏期减少。样本为15名受试者，每种条件约180次试验，使用3.33°直径的刺激，在低至3.13%的对比度下诱发了-0.46 μV的可靠C1振幅，在100%对比度下诱发了-4.82 μV的可靠C1振幅。一个实际的含义是，通过放置不同大小的刺激，以目标有利的距状皮质位点，强大的V1反应可以测量在对比接近感知阈值，这可以大大促进早期视觉感知和注意的原则性研究。
Decades of intracranial electrophysiological investigation into the primary visual cortex (V1) have produced many fundamental insights into the computations carried out in low-level visual circuits of the brain. Some of the most important work has been simply concerned with the precise measurement of neural response variations as a function of elementary stimulus attributes such as contrast and size. Surprisingly, such simple but fundamental characterization of V1 responses has not been carried out in human electrophysiology. Here we report such a detailed characterization for the initial “C1” component of the scalp-recorded visual evoked potential (VEP). The C1 is known to be dominantly generated by initial afferent activation in V1, but is difficult to record reliably due to interindividual anatomical variability. We used pattern-pulse multifocal VEP mapping to identify a stimulus position that activates the left lower calcarine bank in each individual, and afterwards measured robust negative C1s over posterior midline scalp to gratings presented sequentially at that location. We found clear and systematic increases in C1 peak amplitude and decreases in peak latency with increasing size as well as with increasing contrast. With a sample of 15 subjects and ~180 trials per condition, reliable C1 amplitudes of −0.46μV were evoked at as low a contrast as 3.13% and as large as −4.82μV at 100% contrast, using stimuli of 3.33° diameter. A practical implication is that by placing sufficiently-sized stimuli to target favorable calcarine cortical loci, robust V1 responses can be measured at contrasts close to perceptual thresholds, which could greatly facilitate principled studies of early visual perception and attention.
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