Neural Correlates of Perceptual Similarity Masking in Primate V1

Data set and code for journal paper of the same name in eLife: Visual detection is a fundamental natural task. Detection becomes more challenging as the similarity between the target and the background in which it is embedded increases, a phenomenon termed “similarity masking”. To test the hypothesis that V1 contributes to similarity masking, we used voltage sensitive dye imaging (VSDI) to measure V1 population responses while macaque monkeys performed a detection task under varying levels of target-background similarity. Paradoxically, we find that during an initial transient phase, V1 responses to the target are enhanced, rather than suppressed, by target-background similarity. This effect reverses in the second phase of the response, so that in this phase V1 signals are positively correlated with the behavioral effect of similarity. Finally, we show that a simple model with delayed divisive normalization can qualitatively account for our findings. Overall, our results support the hypothesis that a nonlinear gain control mechanism in V1 contributes to perceptual similarity masking.本数据集与代码对应发表于《eLife》期刊的同名论文： 视觉检测是一项基础自然任务。当目标与其所处背景的相似度升高时，检测任务的难度会随之提升，这一现象被称为“相似度掩蔽（similarity masking）”。为验证初级视觉皮层（V1）参与相似度掩蔽的假说，我们采用电压敏感染料成像（VSDI）技术，在猕猴完成不同目标-背景相似度水平下的检测任务时，记录V1神经元群体的响应。出乎意料的是，在响应的初始瞬时阶段，目标-背景相似度会增强而非抑制V1对目标的响应。该效应在响应的第二阶段发生反转，因此在此阶段V1信号与相似度的行为效应呈正相关。最终我们证实，一个带有延迟除法归一化（divisive normalization）的简单模型可以定性地解释我们的实验发现。总体而言，我们的结果支持这一假说：V1内的非线性增益控制机制参与了知觉层面的相似度掩蔽。