PNAS：睡眠中大脑的对话

美国布朗大学的科学家 在最新一期出刊的PNAS 期刊中，发表最新的一份研究报告指出，透过一项记录技术(recording technique) 的发展，科学家成功的录到大脑不同区域的对话，因而有可能揭开记忆储存的秘密。

长久以来科学家就对于大脑的记忆模式，感到高度的兴趣，就过去相关研究的推论，大脑中不同区域的功能不同。就大脑的记忆工作来说，有的区域具有短期记忆的功能，有的区域则被认为是储存记忆的地方，这次布朗大学 Mayank Mehta教授所主导的研究计划，首先是发现了睡眠中的脑部电流活动，并非随机无规则的放电，研究人员利用小鼠的睡眠实验，确定俗称海马回 (hippocampus)的脑部区域，会缓慢而规律的向新皮质 (neocortex)脑区放出微弱的电流讯号，而新皮质脑区也会因应这些刺激，发出一定的响应反应，来自德国 Max Planck Institute 共同参与这个研究计划的Bert Sakmann 博士，利用新发展出来的记录系统，以一个深入新皮质脑区的电极，和3 个分怖于海马回脑区的电极，进一步分析这些往返的神经电位讯号，结果发现新皮质脑区所发出的响应反应和原始的刺激并不相同。

参与的科学家怀疑这些讯号传讯的过程，就像是大脑不同区域的对话一般，而这个在睡眠时间发生的讯号，虽然仍无法了解，是否跟记忆的储存有关，但肯定这是进一步了解大脑功能的新方向。

(资料来源 : Bio.com)

部分英文原文：

Published online before print March 12, 2007

Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0700222104

Differential responses of hippocampal subfields to cortical up-down states

( consolidation | hippocampus | neocortex | oscillation | sleep )

Thomas T. G. Hahn *, Bert Sakmann *, and Mayank R. Mehta

*Department of Cell Physiology, Max Planck Institute for Medical Research, D-69120 Heidelberg, Germany; and Department of Neuroscience, Brown University, Providence, RI 02912

Communicated by Mortimer Mishkin, National Institutes of Health, Bethesda, MD, January 9, 2007 (received for review October 9, 2006)

The connectivity of the hippocampal trisynaptic circuit, formed by the dentate gyrus, the CA3 and the CA1 region, is well characterized anatomically and functionally in vitro. The functional connectivity of this circuit in vivo remains to be understood. Toward this goal, we investigated the influence of the spontaneous, synchronized oscillations in the neocortical local field potential, reflecting up-down states (UDS) of cortical neurons, on the hippocampus. We simultaneously measured the extracellular local field potential in association cortex and the membrane potential of identified hippocampal excitatory neurons in anesthetized mice. Dentate gyrus granule cells showed clear UDS modulation that was phase locked to cortical UDS with a short delay. In contrast, CA3 pyramidal neurons showed mixed UDS modulation, such that some cells were depolarized during the cortical up state and others were hyperpolarized. CA1 pyramidal neurons, located farther downstream, showed consistent UDS modulation, such that when the cortical and dentate gyrus neurons were depolarized, the CA1 pyramidal cells were hyperpolarized. These results demonstrate the differential functional connectivity between neocortex and hippocampal subfields during UDS oscillations.