Humans spend hours each day spontaneously engaging with visual content, free from specific tasks and at their own pace. Currently, the brain mechanisms determining the duration of self-paced perceptual behavior remain largely unknown. Here, participants viewed naturalistic images under task-free settings and self-paced each image's viewing duration while undergoing EEG and pupillometry recordings. Across two independent data sets, we observed large inter- and intra-individual variability in viewing duration. However, beyond an image's presentation order and category, specific image content had no consistent effects on spontaneous viewing duration across participants. Overall, longer viewing durations were associated with sustained enhanced posterior positivity and anterior negativity in the ERPs. Individual-specific variations in the spontaneous viewing duration were consistently correlated with evoked EEG activity amplitudes and pupil size changes. By contrast, presentation order was selectively correlated with baseline alpha power and baseline pupil size. Critically, spontaneous viewing duration was strongly predicted by the temporal stability in neural activity patterns starting as early as 350 msec after image onset, suggesting that early neural stability is a key predictor for sustained perceptual engagement. Interestingly, neither bottom–up nor top–down predictions about image category influenced spontaneous viewing duration. Overall, these results suggest that individual-specific factors can influence perceptual processing at a surprisingly early time point and influence the multifaceted ebb and flow of spontaneous human perceptual behavior in naturalistic settings.

中文翻译：

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决定无任务、自定进度视觉感知持续时间的神经机制

人们每天会花几个小时自发地参与视觉内容，不受特定任务的影响，按照自己的节奏进行。目前，决定自定进度感知行为持续时间的大脑机制仍然很大程度上未知。在这里，参与者在无任务设置下观看自然图像，并在进行脑电图和瞳孔测量记录时自定每张图像的观看持续时间。在两个独立的数据集中，我们观察到观看持续时间存在很大的个体间和个体内差异。然而，除了图像的呈现顺序和类别之外，特定的图像内容对参与者的自发观看持续时间没有一致的影响。总体而言，较长的观看时间与 ERP 中后部阳性和前部阴性的持续增强相关。自发观看持续时间的个体特异性变化与诱发的脑电图活动幅度和瞳孔大小变化一致相关。相比之下，呈现顺序选择性地与基线阿尔法功率和基线瞳孔大小相关。重要的是，自发观看持续时间可以通过图像出现后 350 毫秒开始的神经活动模式的时间稳定性来强烈预测，这表明早期神经稳定性是持续感知参与的关键预测因素。有趣的是，关于图像类别的自下而上和自上而下的预测都不会影响自发观看持续时间。总体而言，这些结果表明，个体特定因素可以在令人惊讶的早期时间点影响感知处理，并影响自然环境中人类自发感知行为的多方面潮起潮落。