Repeated stimuli elicit attenuated responses in visual cortex relative to novel stimuli. This adaptation can be considered as a form of rapid learning and a signature of perceptual memory. Adaptation occurs not only when a stimulus is repeated immediately, but also when there is a lag in terms of time and other intervening stimuli before the repetition. But how does the visual system keep track of which stimuli are repeated, especially after long delays and many intervening stimuli? We hypothesized that the hippocampus and medial temporal lobe (MTL) support long-lag adaptation, given that this memory system can learn from single experiences, maintain information over delays, and send feedback to visual cortex. We tested this hypothesis with fMRI in an amnesic patient, LSJ, who has encephalitic damage to the MTL resulting in extensive bilateral lesions including complete hippocampal loss. We measured adaptation at varying time lags between repetitions in functionally localized visual areas that were intact in LSJ. We observed that these areas track information over a few minutes even when the hippocampus and extended parts of the MTL are unavailable. LSJ and controls were identical when attention was directed away from the repeating stimuli: adaptation occurred for lags up to three minutes, but not six minutes. However, when attention was directed toward stimuli, controls now showed an adaptation effect at six minutes but LSJ did not. These findings suggest that visual cortex can support one-shot perceptual memories lasting for several minutes but that the hippocampus and surrounding MTL structures are necessary for adaptation in visual cortex after longer delays when stimuli are task-relevant.

重复刺激引起视觉皮层相对于新刺激减弱的反应。这种适应可以被视为一种快速学习的形式和知觉记忆的特征。适应不仅发生在立即重复刺激时，而且发生在重复之前的时间和其他干预刺激存在滞后时。但是视觉系统如何跟踪哪些刺激是重复的，尤其是在长时间延迟和许多干预刺激之后？我们假设海马体和内侧颞叶 (MTL) 支持长滞后适应，因为这个记忆系统可以从单一经验中学习，保持信息延迟，并将反馈发送到视觉皮层。我们在一个健忘症患者 LSJ 中用 fMRI 检验了这个假设，对 MTL 有脑炎性损伤，导致广泛的双侧病变，包括完全的海马损失。我们在 LSJ 中完整的功能局部视觉区域的重复之间的不同时间滞后测量了适应。我们观察到，即使海马体和 MTL 的扩展部分不可用，这些区域也会在几分钟内跟踪信息。当注意力远离重复刺激时，LSJ 和对照是相同的：适应发生的滞后长达 3 分钟，但不是 6 分钟。然而，当注意力转向刺激时，对照现在在 6 分钟时显示出适应效果，而 LSJ 则没有。