Neural Substrates Of Stimulus Recognition And Association Memory

周围皮层接收来自单峰感觉区域的输入，如TE区域（在颜色和形状视觉中起关键作用）和尾端颗粒状岛叶皮层（在触觉中起关键作用），以及来自多峰区域的输入，包括扣带皮层和眶额叶皮层。本部分的早期工作确定了嗅周皮层在将物体的不同感官品质联系在一起（例如触觉-视觉联系）中的作用。这项研究表明，嗅周皮层对物体识别很重要，但对于嗅周皮层在感知和记忆中的作用却不明确。最近，我们的工作表明，周围皮层并不像传统认为的那样，作为MTL的一部分，专门为陈述性记忆过程服务，而是在感知过程和记忆中发挥作用。我们发现单个物体的知觉识别依赖于周围皮层（Bussey et al., 2002,2003）。换句话说，我们已经发现了推翻上述MTL记忆系统观点第一个命题的证据。

The perirhinal cortex receives inputs from both unimodal sensory areas such as area TE (which plays a key role in color and form vision) and the caudal, granular insular cortex (which plays a key role in touch), as well as from multimodal regions including the cingulate cortex and orbital frontal cortex. Earlier work in this Section identified a role for perirhinal cortex in associating together the different sensory qualities of objects (e.g. tactual-visual associations). This work indicated that perirhinal cortex was important for object identification, but was equivocal regarding a role for perirhinal cortex in perception versus memory. More recently, our work showed that the perirhinal cortex does not, as conventionally thought, exclusively subserve declarative memory processes as part of the MTL, but rather functions in perceptual processes as well as in memory. We found that perceptual identification of individual objects depends on perirhinal cortex (Bussey et al., 2002, 2003). In other words, we have uncovered evidence that overturns the first proposition of the MTL memory system view, outlined above. The findings from recent studies were consistent with our predictions based on a hierarchical organization of representations in the ventral visual stream or object-analyzer pathway. One additional prediction of this hierarchical organization is that the perirhinal cortex should also be essential for associating together two different objects or images, especially if they occur together in a visual scene. To test this idea we presented subjects with overlapping pairs of objects (A vs B, B vs. C, C vs. A) in the context of a concurrent visual discrimination. In this task, the identity of the pair presented on any given trial indicates which object will be correct. (For example, if B is paired with A, then A is correct, but if B is paired with C, then B is correct.) To choose correctly, then, subjects need to associate the objects comprising a pair, i.e., to represent them together. Using this test design, we found that damage to perirhinal cortex impairs, and damage to the hippocampus facilitates, learning the concurrent discriminations. This project made progress in two main ways. First, we confirmed and extended our earlier work by showing that perirhinal cortex is essential not only for representing the conjunctions of features that compose individual objects, but also for representing the conjunctions of objects that compose visual scenes. Together with our earlier results, these findings argue against the first proposition of the prevailing MTL memory system view. Contrary to that view, the perirhinal cortex appears to play a role in representing information about objects for both mnemonic and perceptual purposes. Second, we found that damage to the perirhinal cortex and hippocampus have opposing effects on memory. Thus, the second proposition of the prevailing view that MTL components contribute roughly equally to declarative memory has also been contradicted. Instead, the results support the perceptual-mnemonic view, which holds that perirhinal cortex has a role in visual perception as well as memory, and that it is part of both the MTL and the ventral visual stream.