Rudd Michael E, Shareef Idris
Department of Psychology, University of Nevada, Reno, NV 89557, United States; Center for Integrative Neuroscience, University of Nevada, Reno, NV 89557, United States.
Department of Psychology, University of Nevada, Reno, NV 89557, United States.
Vision Res. 2025 Feb;227:108517. doi: 10.1016/j.visres.2024.108517. Epub 2025 Jan 6.
A neural theory of human lightness computation is described and computer-simulated. The theory proposes that lightness is derived from transient ON and OFF cell responses in the early visual pathways that have different characteristic neural gains and that are generated by fixational eye movements (FEMs) as the eyes transit luminance edges in the image. The ON and OFF responses are combined with corollary discharge signals that encode the eye movement direction to create directionally selective ON and OFF responses. Cortical neurons with large-scale receptive fields independently integrate the outputs of all of the directional ON or OFF responses whose associated eye movement directions point towards their receptive field centers, with a spatial weighting determined by the receptive field profile. Lightness is computed by subtracting the spatially integrated OFF activity from spatially integrated ON activity and normalizing the difference signal so that the maximum response in the spatial lightness map at any given time equals a fixed activation level corresponding to the percept of white. Two different mechanisms for ON and OFF cells responses are considered and simulated, and both are shown to produce an overall lightness model that explains a host of quantitative and qualitative lightness phenomena, including the Staircase Gelb and related illusions, failures of lightness constancy in the simultaneous contrast illusion, Chevreul's illusion, lightness filling-in, and perceptual fading of stabilized images. The neural plausibility of the two variants of the theory, as well as its implication for lightness constancy and failures of lightness constancy are discussed.
本文描述并通过计算机模拟了一种关于人类明度计算的神经理论。该理论提出，明度源自早期视觉通路中瞬态的开细胞和关细胞反应，这些细胞具有不同的特征神经增益，并且是在眼睛在图像中跨越亮度边缘时由注视性眼动（FEMs）产生的。开反应和关反应与编码眼动方向的伴随放电信号相结合，以创建方向选择性的开反应和关反应。具有大规模感受野的皮层神经元独立地整合所有方向开反应或关反应的输出，这些反应相关的眼动方向指向其感受野中心，其空间加权由感受野轮廓决定。通过从空间整合的开活动中减去空间整合的关活动，并对差异信号进行归一化来计算明度，以便在任何给定时间空间明度图中的最大反应等于对应于白色感知的固定激活水平。考虑并模拟了开细胞和关细胞反应的两种不同机制，结果表明这两种机制都能产生一个整体明度模型，该模型解释了许多定量和定性的明度现象，包括楼梯格尔伯错觉及相关错觉、同时对比错觉中明度恒常性的失效、谢弗勒尔错觉、明度填充以及稳定图像的感知消退。本文还讨论了该理论的两种变体在神经学上的合理性，以及它对明度恒常性和明度恒常性失效的影响。
