Radboud University Nijmegen, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, Netherlands.
Elife. 2023 Feb 2;12:e78904. doi: 10.7554/eLife.78904.
Human agents build models of their environment, which enable them to anticipate and plan upcoming events. However, little is known about the properties of such predictive models. Recently, it has been proposed that hippocampal representations take the form of a predictive map-like structure, the so-called successor representation (SR). Here, we used human functional magnetic resonance imaging to probe whether activity in the early visual cortex (V1) and hippocampus adhere to the postulated properties of the SR after visual sequence learning. Participants were exposed to an arbitrary spatiotemporal sequence consisting of four items (A-B-C-D). We found that after repeated exposure to the sequence, merely presenting single sequence items (e.g., - B - -) resulted in V1 activation at the successor locations of the full sequence (e.g., C-D), but not at the predecessor locations (e.g., A). This highlights that visual representations are skewed toward future states, in line with the SR. Similar results were also found in the hippocampus. Moreover, the hippocampus developed a coactivation profile that showed sensitivity to the temporal distance in sequence space, with fading representations for sequence events in the more distant past and future. V1, in contrast, showed a coactivation profile that was only sensitive to spatial distance in stimulus space. Taken together, these results provide empirical evidence for the proposition that both visual and hippocampal cortex represent a predictive map of the visual world akin to the SR.
人类代理构建环境模型,使他们能够预测和规划即将发生的事件。然而,对于这种预测模型的特性知之甚少。最近,有人提出海马体的表示形式是一种预测地图样结构,即所谓的后继者表示(SR)。在这里,我们使用人类功能磁共振成像来探测视觉序列学习后,早期视觉皮层(V1)和海马体的活动是否符合 SR 的假定特性。参与者接触到由四个项目(A-B-C-D)组成的任意时空序列。我们发现,在反复暴露于序列后,仅呈现单个序列项(例如,-B--)会导致 V1 在完整序列的后继位置(例如,C-D)而不是在先行位置(例如,A)处激活。这突出表明,视觉表示偏向于未来状态,符合 SR。在海马体中也发现了类似的结果。此外,海马体形成了一种共激活模式,该模式对序列空间中的时间距离敏感,对于过去和未来更远的序列事件的表示逐渐消失。相比之下,V1 的共激活模式仅对刺激空间中的空间距离敏感。总之,这些结果为视觉和海马体皮层都代表类似于 SR 的视觉世界的预测图的命题提供了经验证据。