Department of Brain and Cognitive Sciences, Seoul National University, Seoul, South Korea.
Department of Biomedical Science, Charles E. Schmidt College of Medicine, Brain Institute, Florida Atlantic University, Jupiter, Florida, USA.
Hippocampus. 2021 Jul;31(7):717-736. doi: 10.1002/hipo.23295. Epub 2021 Jan 4.
The hippocampus and parahippocampal region are essential for representing episodic memories involving various spatial locations and objects, and for using those memories for future adaptive behavior. The "dual-stream model" was initially formulated based on anatomical characteristics of the medial temporal lobe, dividing the parahippocampal region into two streams that separately process and relay spatial and nonspatial information to the hippocampus. Despite its significance, the dual-stream model in its original form cannot explain recent experimental results, and many researchers have recognized the need for a modification of the model. Here, we argue that dividing the parahippocampal region into spatial and nonspatial streams a priori may be too simplistic, particularly in light of ambiguous situations in which a sensory cue alone (e.g., visual scene) may not allow such a definitive categorization. Upon reviewing evidence, including our own, that reveals the importance of goal-directed behavioral responses in determining the relative involvement of the parahippocampal processing streams, we propose the Goal-directed Interaction of Stimulus and Task-demand (GIST) model. In the GIST model, input stimuli such as visual scenes and objects are first processed by both the postrhinal and perirhinal cortices-the postrhinal cortex more heavily involved with visual scenes and perirhinal cortex with objects-with relatively little dependence on behavioral task demand. However, once perceptual ambiguities are resolved and the scenes and objects are identified and recognized, the information is then processed through the medial or lateral entorhinal cortex, depending on whether it is used to fulfill navigational or non-navigational goals, respectively. As complex sensory stimuli are utilized for both navigational and non-navigational purposes in an intermixed fashion in naturalistic settings, the hippocampus may be required to then put together these experiences into a coherent map to allow flexible cognitive operations for adaptive behavior to occur.
海马体和旁海马区对于代表涉及各种空间位置和物体的情景记忆，以及对于使用这些记忆来进行未来的适应性行为是必不可少的。“双信息流模型”最初是根据内侧颞叶的解剖学特征制定的，将旁海马区分成两个信息流，分别处理和传递空间和非空间信息到海马体。尽管该模型意义重大，但原始形式的双信息流模型不能解释最近的实验结果，许多研究人员已经认识到需要对该模型进行修改。在这里，我们认为，将旁海马区分为空间和非空间信息流可能过于简单化，特别是在只有单一感觉线索（例如，视觉场景）的情况下，这种分类可能并不明确的情况下。在回顾证据时，包括我们自己的证据，这些证据揭示了目标导向的行为反应在确定旁海马处理信息流的相对参与程度方面的重要性，我们提出了目标导向的刺激和任务需求相互作用（GIST）模型。在 GIST 模型中，输入刺激，如视觉场景和物体，首先由后眶回和旁眶回皮质处理——后眶回皮质更多地参与视觉场景，旁眶回皮质更多地参与物体，而相对较少地依赖于行为任务需求。然而，一旦感知上的模糊性得到解决，并且场景和物体被识别和认知，信息就会通过内侧或外侧内嗅皮质处理，这取决于它是用于实现导航还是非导航目标。由于在自然环境中，复杂的感觉刺激以混合的方式用于导航和非导航目的，因此海马体可能需要将这些经验整合到一个连贯的地图中，以便为适应性行为的发生提供灵活的认知操作。
