Studies on the neuronal mechanisms of the memory functions in the amygdala and the uippocampus of monkeys

杏仁核和海马体的记忆功能已经在人类患者和非人类灵长类动物中进行了研究。在这些实验中，在脑组织的手术或缺血性损伤后进行心理测试以发现记忆功能的缺陷。这些实验呈现出两种相互矛盾的结果。米什金的团队强调了这两种结构的重要性。另一方面，Zola-Morgan的研究小组强调海马的作用。因为在这些与记忆任务相关的结构中从未记录到神经元活动，所以不清楚哪一个是正确的。本研究记录了恒河猴在视觉短时记忆任务中杏仁核和海马的神经元活动。我们在杏仁核中发现了选择性的记忆神经元，它们对特定的刺激产生反应，并贯穿随后的记忆过程，但在海马体中没有。除了这些神经元外，我们还发现了非选择性延迟神经元，它们在延迟期内放电频率逐渐增加，在下一次刺激后放电频率下降。结论：杏仁核参与了视觉短时记忆的保持，而海马不直接参与视觉短时记忆的保持。

The memory functions in the amygdala and the hippocampus has been studied in the human patient and non-human primates. In these experiments, psychological tests to find the deficits of memory functions were performed after the surgical or ishemic lesion of the brain tissues. There were two kinds of contradictory results have been presented by these experiments. Mishkin's group are emphasizing the importance of both structures. On the other hand, Zola-Morgan's group are emphasizing the role of hippocampus. Because neuronal activities were never recorded in these structures related to the memory task, it was not clear which is correct. In this study, the neuronal activities were recorded from the amygdala and hippocampus of the rhesus monkeys during the performance of visual short-term memory task. We found the selective memory neurons which fired i n response to particular photograph-and throughout the subseqtrent memory periods in the amygdala but not in the hippocampus. In addition to these neurons, we found the non-selective delay neurons which showed increase of their discharge rates gradually during the delay period and the discharge rate decreased after the next stimulus in both of structures. We concluded that the amygdala was involved in the retention of the visual short-term memory, but the hippocampus was not directly involved in the retention of the visual memory.