Medical Faculty, Department of Neurophysiology, Ruhr University Bochum, Bochum, Germany.
International Graduate School of Neuroscience, Ruhr University Bochum, Bochum, Germany.
Hippocampus. 2021 Aug;31(8):897-915. doi: 10.1002/hipo.23333. Epub 2021 May 8.
Learning about general aspects, or content details, of space results in differentiated neuronal information encoding within the proximodistal axis of the hippocampus. These processes are tightly linked to long-term potentiation (LTP) and long-term depression (LTD). Here, we explored the precise sites of encoding of synaptic plasticity in the hippocampus that are mediated by information throughput from the perforant path. We assessed nuclear Homer1a-expression that was triggered by electrophysiological induction of short and long forms of hippocampal synaptic plasticity, and compared it to Homer1a-expression that was triggered by LTP and LTD enabled by different forms of spatial learning. Plasticity responses were induced by patterned stimulation of the perforant path and were recorded in the dentate gyrus (DG) of freely behaving rats. We used fluorescence in situ hybridization to detect experience-dependent nuclear encoding of Homer1a in proximodistal hippocampal subfields. Induction of neither STP nor STD resulted in immediate early gene (IEG) encoding. Electrophysiological induction of robust LTP, or LTD, resulted in highly significant and widespread induction of nuclear Homer1a in all hippocampal subfields. LTP that was facilitated by novel spatial exploration triggered similar widespread Homer1a-expression. The coupling of synaptic depression with the exploration of a novel configuration of landmarks resulted in localized IEG expression in the proximal CA3 region and the lower (infrapyramidal) blade of the DG. Our findings support that synaptic plasticity induction via perforant path inputs promotes widespread hippocampal information encoding. Furthermore, novel spatial exploration promotes the selection of a hippocampal neuronal network by means of LTP that is distributed in an experience-dependent manner across all hippocampus subfields. This network may be modified during spatial content learning by LTD in specific hippocampal subfields. Thus, long-term plasticity-inducing events result in IEG expression that supports establishment and/or restructuring of neuronal networks that are necessary for long-term information storage.
学习空间的一般方面或内容细节会导致海马体的近-远轴内神经元信息编码的差异。这些过程与长时程增强（LTP）和长时程抑制（LTD）紧密相关。在这里，我们探索了由穿通纤维通路信息传递介导的海马体中突触可塑性的精确编码部位。我们评估了电生理学诱导的短时间和长时间海马突触可塑性引发的核 Homer1a 表达，并将其与由不同形式的空间学习引发的 LTP 和 LTD 引发的 Homer1a 表达进行了比较。通过对穿通纤维通路进行模式刺激来诱导可塑性反应，并在自由活动大鼠的齿状回（DG）中进行记录。我们使用荧光原位杂交来检测 Homer1a 在近-远海马亚区的经验依赖性核编码。无论是 STP 还是 STD 的诱导都不会导致即时早期基因（IEG）编码。强大的 LTP 或 LTD 的电生理学诱导会导致所有海马亚区的核 Homer1a 高度显著和广泛的诱导。由新的空间探索促进的 LTP 会引发类似的广泛 Homer1a 表达。将突触抑制与地标新配置的探索相结合，会导致 CA3 近端区和 DG 的下部（下棘）产生局部 IEG 表达。我们的研究结果支持通过穿通纤维通路输入诱导的突触可塑性会促进广泛的海马体信息编码。此外，新的空间探索通过在所有海马体亚区以经验依赖的方式分布的 LTP 促进了海马体神经元网络的选择。该网络可能会在特定海马体亚区的 LTD 过程中在空间内容学习期间发生改变。因此，长期的可塑性诱导事件会导致 IEG 表达，从而支持用于长期信息存储的神经元网络的建立和/或重构。
