Role of the Hippocampus, Amygdala, and Entorhinal Cortex in Memory Storage and Expression

In the brain, spreading depression (SD) is characterized by a large extracellular DC shift, a massive failure of ion homeostasis and a transient cessation of neuronal function. Clinically, SD is believed to be involved in various neurological disorders including migraine and cerebrovascular diseases. The propagation of cortical SD requires the release of glutamate, and N-methyl-d-aspartate (NMDA) receptors play a crucial role in this process. Here, we have isolated the NMDA receptor-mediated component of extracellularly recorded field excitatory postsynaptic potentials (fEPSPs) in layers 2–3 of the entorhinal cortex of murine brain slices. In the absence of GABAA and AMPA receptor-mediated synaptic transmission, stimulation of layer 6 afferents every 15–90 s elicited spontaneous SD on average within 18.5 min after the start of the stimulation. In the presence of ifenprodil, an NR2B receptor subunit-selective NMDA receptor antagonist, the occurrence of SD was nearly abolished. Our results are consistent with an important role of NR2B subunits in triggering SD in the entorhinal cortex.

Download Full-text

Complementary learning systems within the hippocampus: A neural network modeling approach to reconciling episodic memory with statistical learning

10.1101/051870 ◽

2016 ◽

Cited By ~ 7

Author(s):

Anna C. Schapiro ◽

Nicholas B. Turk-Browne ◽

Matthew M. Botvinick ◽

Kenneth A. Norman

Keyword(s):

Neural Network ◽

Statistical Learning ◽

Entorhinal Cortex ◽

Network Modeling ◽

Learning Systems ◽

Neural Network Modeling ◽

Trade Off ◽

Rapid Learning ◽

Rapid Extraction

AbstractA growing literature suggests that the hippocampus is critical for the rapid extraction of regularities from the environment. Although this fits with the known role of the hippocampus in rapid learning, it seems at odds with the idea that the hippocampus specializes in memorizing individual episodes. In particular, the Complementary Learning Systems theory argues that there is a computational trade-off between learning the specifics of individual experiences and regularities that hold across those experiences. We asked whether it is possible for the hippocampus to handle both statistical learning and memorization of individual episodes. We exposed a neural network model that instantiates known properties of hippocampal projections and subfields to sequences of items with temporal regularities. We found that the monosynaptic pathway — the pathway connecting entorhinal cortex directly to region CA1 — was able to support statistical learning, while the trisynaptic pathway — connecting entorhinal cortex to CA1 through dentate gyrus and CA3 — learned only individual episodes, with apparent representations of regularities resulting from associative reactivation through recurrence. Thus, in paradigms involving rapid learning, the computational trade-off between learning episodes and regularities may be handled by separate anatomical pathways within the hippocampus itself.

Download Full-text

Telencephalic outputs from the medial entorhinal cortex are copied directly to the hippocampus

10.1101/2021.03.10.434566 ◽

2021 ◽

Author(s):

Sau Yee Tsoi ◽

Merve Öncül ◽

Ella Svahn ◽

Mark Robertson ◽

Zuzanna Bogdanowicz ◽

...

Keyword(s):

Entorhinal Cortex ◽

Memory Consolidation ◽

Memory Storage ◽

Medial Entorhinal Cortex ◽

Ca1 Region ◽

Deep Layers ◽

Standard Models

AbstractStandard models for memory storage assume that signals reach the hippocampus from superficial layers of the entorhinal cortex (EC) and are returned to the telencephalon by projections from deep layers of the EC. Here we show that telencephalon-projecting cells in Layer 5a of the medial EC send a copy of their outputs back to the CA1 region of the hippocampus. Our results suggest that rather than serving as a relay, deep EC may coordinate hippocampal-neocortical interactions in memory consolidation.

Download Full-text

The Axial Age, Axiality, and the Missionary Enterprise

International Bulletin of Mission Research ◽

10.1177/2396939316675574 ◽

2016 ◽

Vol 41 (1) ◽

pp. 63-72

Author(s):

David Lindenfeld

Keyword(s):

Recent Literature ◽

World History ◽

Memory Storage ◽

External Memory ◽

Broad Perspective ◽

The Third ◽

Axial Age ◽

Third Stage ◽

Brain Culture

This article reviews recent literature on the Axial Age as a phase of world history and seeks to illuminate the role of Christian missionaries as part of this broad perspective. Introduced by Karl Jaspers in 1949, the concept has attracted attention from scholars interested in human development. The cognitive psychologist Merlin Donald views it as the third stage of “brain-culture co-evolution,” which draws on the external memory storage that literacy provides. I argue that missionaries have been central agents in conveying such stored knowledge to non-axial cultures.

Download Full-text