Neural mechanisms of cognitive memory system : Integration of functional magnetic resonance imaging method and molecular / allular approaches

1.在灵长类动物中，物体的视觉长期记忆可能存储在下颞叶（IT）皮层中。由于脑源性神经营养因子（BDNF）参与活动依赖性神经重组，我们测试的假设，BDNF将上调IT皮层在视觉配对联想记忆的形成。为了消除个体动物之间的遗传和认知差异，我们使用裂脑猴进行基于PCR的mRNA定量的动物内比较。这些猴子使用一个半球学习配对联想（PA）任务，使用另一个半球学习控制视觉任务，以平衡视觉输入的数量。我们发现，在PA学习过程中，脑源性神经营养因子在IT皮层的36区选择性上调，但在视觉处理的早期阶段所涉及的领域没有上调。结果表明，BDNF有助于灵长类动物中视觉长期记忆形成的神经回路的重组（Tokuyama等人，Nature neuroscience 3，1134-1142，2000）。 ...更多信息 新皮层和边缘皮层之间的双向信号传递被认为有助于长时记忆的恢复。我们测试了这一假设，通过比较的时间过程中的知觉和记忆检索信号在颞叶皮层，区域TE（TE）和嗅周皮层（PRh）的两个相邻区域，而猴子正在执行的视觉配对联想任务。感知信号在PRh之前到达TE，确认其向前传播。与此相反，记忆检索信号出现在PRh较早，TE神经元，然后逐渐招募代表所寻求的目标。对这一发现的合理解释是，从PRh到TE的丰富的向后纤维投射可能是代表从长期记忆中检索的视觉对象的TE神经元的激活的基础（Naya，Yoshida & Miyashita，Science 291，661-664，2001）。通过功能磁共振成像直接比较了猕猴和人类的脑功能组织。这两个物种的主题进行了修改后的威斯康星州卡片分类测试，需要在认知集转移的形式行为的灵活性。对两种动物使用相同的视觉刺激和任务序列。我们在猴子和人类的前额叶皮层的焦点区域发现了与认知定势转换相关的短暂激活。这些功能的同源物位于cytoarchitectonically在腹外侧前额叶皮质后部的等效区域。这种比较成像提供了对灵长类动物认知进化的见解（Nakahara，Hayashi，Konishi & Miyashita，Science 295，1532-1536，2002）。少

1. In primates, visual long-term memory of objects is presumably stored in the inferior temporal (IT) cortex. Because brain-derived neurotrophic factor (BDNF) is involved in activity-dependent neural reorganization, we tested the hypothesis that BDNF would be upregulated in IT cortex during formation of visual pair-association memory. To eliminate genetic and cognitive variations between individual animals, we used split-brain monkeys for intra-animal comparison in PCR-based mRNA quantitation. The monkeys learned a pair-association (PA) task using one hemisphere and a control visual task using the other, to balance the amount of visual input. We found that BDNF was upregulated selectively in area 36 of IT cortex during PA learning, but not in areas involved in earlier stages of visual processing. The results suggest that BDNF contributes to reorganization of neural circuits for visual long-term memory formation in the primate (Tokuyama et al. Nature neuroscience 3, 1134-1142, 2000).2. … More Bidirectional signaling between neocortex and limbic cortex has been hypothesized to contribute to the retrieval of long-term memory. We tested this hypothesis by comparing the time courses of perceptual and memory-retrieval signals in two neighboring areas in temporal cortex, area TE (TE) and perirhinal cortex (PRh), while monkeys were performing a visual pair-association task. Perceptual signal reached TE before PRh, confirming its forward propagation. In contrast, memory-retrieval signal appeared earlier in PRh, and TE neurons were then gradually recruited to represent the sought target. A reasonable interpretation of this finding is that the rich backward fiber projections from PRh to TE may underlie the activation of TE neurons that represent a visual object retrieved from long-term memory (Naya, Yoshida ＆ Miyashita, Science 291, 661-664, 2001).3. Functional brain organization of macaque monkeys and humans was directly compared by functional magnetic resonance imaging. Subjects of both species performed a modified Wisconsin Card Sorting Test that required behavioral flexibility in the form of cognitive set shifting. Equivalent visual stimuli and task sequence were used for the two species. We found transient activation related to cognitive set shifting in focal regions of prefrontal cortex in both monkeys and humans. These functional homologs were located in cytoarchitectonically equivalent regions in the posterior part of ventrolateral prefrontal cortex. This comparative imaging provides insights into the evolution of cognition in primates (Nakahara, Hayashi, Konishi ＆ Miyashita, Science 295, 1532-1536, 2002). Less