Vilotijević Ana, Mathôt Sebastiaan
Department of Psychology, University of Groningen, 9712TS Groningen, the Netherlands.
Department of Psychology, University of Groningen, 9712TS Groningen, the Netherlands.
Cortex. 2025 Jan;182:112-123. doi: 10.1016/j.cortex.2024.10.008. Epub 2024 Nov 5.
Pupil size is modulated by various cognitive factors such as attention, working memory, mental imagery, and subjective perception. Previous studies examining cognitive effects on pupil size mainly focused on inducing or enhancing a subjective experience of brightness or darkness (for example by asking participants to attend to/memorize a bright or dark stimulus), and then showing that this affects pupil size. Surprisingly, the inverse has never been done; that is, it is still unknown what happens when a subjective experience of brightness or darkness is eliminated or strongly reduced even though bright or dark stimuli are physically present. Here, we aim to answer this question by using perceptual fading, a phenomenon where a visual stimulus gradually fades from visual awareness despite its continuous presentation. The study contains two blocks: Fading and Non-Fading. In the Fading block, participants were presented with black and white patches with a fuzzy outline that were presented at the same location throughout the block, thus inducing strong perceptual fading. In contrast, in the Non-Fading block, the patches switched sides on each trial, thus preventing perceptual fading. Participants covertly attended to one of the two patches, indicated by a cue, and reported the offset of one of a set of circles that are displayed on top. We hypothesized that pupil size will be modulated by covert visual attention in the Non-Fading block, but that this effect will not (or to a lesser extent) arise in the Fading block. We found that covert visual attention to bright/dark does modulate pupil size even during perceptual fading (Fading block), but to a lesser extent than when the perceptual experience of brightness/darkness is preserved (Non-Fading block). This implies that pupil size is always modulated by covert attention, but that the effect decreases as subjective experience of brightness or darkness decreases. In broader terms, this suggests that cognitive modulations of pupil size reflect a mixture of high-level and lower-level visual processing.
瞳孔大小受多种认知因素调节，如注意力、工作记忆、心理意象和主观感知。以往研究认知对瞳孔大小影响时，主要聚焦于诱导或增强明暗的主观体验（例如要求参与者关注/记忆明亮或黑暗刺激），然后证明这会影响瞳孔大小。令人惊讶的是，反向操作从未进行过；也就是说，即便明亮或黑暗刺激实际存在，但当明暗的主观体验被消除或大幅降低时会发生什么，仍然未知。在此，我们旨在通过使用知觉消退来回答这个问题，知觉消退是一种视觉刺激尽管持续呈现但却逐渐从视觉意识中消失的现象。该研究包含两个阶段：消退阶段和非消退阶段。在消退阶段，向参与者呈现带有模糊轮廓的黑白斑块，这些斑块在整个阶段都呈现在同一位置，从而引发强烈的知觉消退。相反，在非消退阶段，斑块在每次试验中都会切换位置，从而防止知觉消退。参与者通过提示暗中关注两个斑块中的一个，并报告显示在顶部的一组圆圈中其中一个的偏移。我们假设在非消退阶段，瞳孔大小会受到暗中视觉注意力的调节，但在消退阶段这种效应不会出现（或程度较小）。我们发现，即使在知觉消退期间（消退阶段），对明亮/黑暗的暗中视觉注意力也会调节瞳孔大小，但程度小于保留明暗知觉体验时（非消退阶段）。这意味着瞳孔大小总是受到暗中注意力调节，但随着明暗主观体验的降低，这种效应会减弱。从更广泛的角度来看，这表明瞳孔大小的认知调节反映了高级和低级视觉处理的混合。
