Effects of top-down influence suppression on behavioral and V1 neuronal contrast sensitivity functions in cats. Jian Ding et al.

The relative contributions of higher-order cortical areas and the primary visual cortex (V1) to visual perception remains poorly understood. In this study, we investigated the top-down influence of area 7 (A7), a high-level visual cortical area of cat, on both the behavioral contrast sensitivity function (CSF) and neuronal contrast sensitivity function estimated from visually evoked field potentials (VEPs) in V1. Top-down influence of A7 was noninvasively modulated using transcranial direct current stimulation (tDCS). We found that suppressing top-down influence with cathode (c)-tDCS but not sham (s)-tDCS of A7 significantly decreased both behavioral and neuronal contrast sensitivities (CS) in the same range of spatial frequencies (SFs), and significantly increased both the behavioral and neuronal contrast thresholds over a range of external noise. The neuronal CSF and TvC were highly correlated with their behavioral counterparts both before and after suppression of the top-down influence. Analysis of the TvC functions based on the Perceptual Template Model (PTM) indicated that suppression of top-down influence increased internal additive noise and the impact of external noise at both the behavioral and neuronal levels. Taken together, these results suggest that top-down influence of A7 increases both behavioral and V1 neuronal contrast sensitivity by reducing internal additive noise and the impact of external noise.

高级皮层区域及初级视觉皮层（V1）对视觉感知的相对贡献，至今仍处于认识模糊的状态。在本研究中，我们探讨了猫的高级视觉皮层区域7（A7）对行为对比敏感度函数（CSF）以及从V1中视觉诱发电场电位（VEPs）估计出的神经元对比敏感度函数的下行影响。通过经颅直流电刺激（tDCS）非侵入性地调节A7的下行影响。我们发现，使用阴极（c）-tDCS抑制A7的下行影响，但非真实（s）-tDCS则不然，显著降低了相同空间频率（SFs）范围内的行为和神经元对比敏感度（CS），并在一系列外部噪声中显著提高了行为和神经元的对比阈值。神经元CSF和 TvC 在抑制下行影响前后均与其行为对应物高度相关。基于感知模板模型（PTM）对TvC函数的分析表明，抑制下行影响增加了行为和神经元层面上的内部加性噪声以及外部噪声的影响。综上所述，这些结果提示A7的下行影响通过减少内部加性噪声和外部噪声的影响，增加了行为和V1神经元的对比敏感度。