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海马CA1区及下托投射至内嗅皮质的可塑性与化生改变。

Plastic and metaplastic changes in the CA1 and subicular projections to the entorhinal cortex.

作者信息

Craig Sarah, Commins Sean

机构信息

Department of Psychology, National University of Ireland, Maynooth, Maynooth, Co. Kildare, Ireland.

出版信息

Brain Res. 2007 May 25;1147:124-39. doi: 10.1016/j.brainres.2007.02.016. Epub 2007 Feb 21.

Abstract

The hippocampal formation (HF) is a brain structure critically involved in memory formation. Two major pathways have been identified in the rat; one projection targets the hippocampus via perirhinal cortex and lateral entorhinal cortex (LEC) while another targets the hippocampus via postrhinal cortex and medial entorhinal cortex (MEC). Areas CA1 and subiculum constitute major output structures of HF and target many cortical structures including EC. These return projections are also anatomically segregated with distinct regions of CA1 and subiculum projecting to either the LEC or MEC. We have previously demonstrated that the projections from CA1 and subiculum to the EC are capable of sustaining short- and long-term plastic changes. Here we detail a physiological topography that exists along the hippocampal output projections, equating well with the known anatomy. Specifically, field excitatory postsynaptic potential (fEPSP) responses in LEC are stronger following distal CA1 and proximal subiculum stimulation, compared to either proximal CA1 or distal subiculum stimulation. In addition, fEPSP responses in MEC are stronger following proximal CA1 stimulation compared to distal CA1. We also demonstrate that the distal CA1-LEC, proximal CA1-MEC and proximal subiculum-LEC projections are all capable of frequency-dependent plastic effects that shift the response from LTD to LTP. In addition, responses in distal CA1-LEC projection seem to show metaplastic capabilities. We discuss the possibility of dissociation between LEC and MEC projections, which may suggest two functional circuits from the HF to the cortex and may have implications in information processing, memory research and hippocampal seizure spread to the cortex.

摘要

海马结构(HF)是一种在记忆形成中起关键作用的脑结构。在大鼠中已确定了两条主要通路;一条投射通过嗅周皮质和外侧内嗅皮质(LEC)靶向海马,而另一条通过嗅后皮质和内侧内嗅皮质(MEC)靶向海马。CA1区和海马下脚构成了HF的主要输出结构,并靶向包括内嗅皮质(EC)在内的许多皮质结构。这些返回投射在解剖学上也有分隔,CA1区和海马下脚的不同区域投射到LEC或MEC。我们之前已经证明,从CA1区和海马下脚到EC的投射能够维持短期和长期的可塑性变化。在这里,我们详细描述了沿海马输出投射存在的一种生理拓扑结构,这与已知的解剖结构非常吻合。具体而言,与近端CA1区或远端海马下脚刺激相比,在远端CA1区和近端海马下脚刺激后,LEC中的场兴奋性突触后电位(fEPSP)反应更强。此外,与远端CA1区刺激相比,在近端CA1区刺激后,MEC中的fEPSP反应更强。我们还证明,远端CA1区-LEC、近端CA1区-MEC和近端海马下脚-LEC投射都能够产生频率依赖性的可塑性效应,使反应从长时程抑制(LTD)转变为长时程增强(LTP)。此外,远端CA1区-LEC投射中的反应似乎表现出元可塑性能力。我们讨论了LEC和MEC投射之间解离的可能性,这可能暗示从HF到皮质的两个功能回路,并且可能对信息处理、记忆研究以及海马癫痫扩散到皮质有影响。

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