Ca3 hippocampus

From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new ca3 hippocampus information within short-term memory with a duration of seconds and minutes.

In the CA3 region of the hippocampus, pyramidal cells excite other pyramidal cells and interneurons. The axons of CA3 pyramidal cells spread throughout most of the region to form an associative network. These connections were first drawn by Cajal and Lorente de No. Their physiological properties were explored to understand epileptiform discharges generated in the region. Synapses between pairs of pyramidal cells involve one or few release sites and are weaker than connections made by mossy fibers on CA3 pyramidal cells.

Ca3 hippocampus

Federal government websites often end in. The site is secure. Human functional magnetic resonance imaging fMRI studies have long investigated the hippocampus without differentiating between its subfields, even though theoretical models and rodent studies suggest that subfields support different and potentially even opposite functions. The CA3 region of the hippocampus has been ascribed a pivotal role both in initially forming associations during encoding and in reconstructing a memory representation based on partial cues during retrieval. These functions have been related to pattern separation and pattern completion, respectively. In recent years, studies using high-resolution fMRI in humans have begun to separate different hippocampal subregions and identify the role of the CA3 subregion relative to the other subregions. However, some of these findings have been inconsistent with theoretical models and findings from electrophysiology. In this review, we describe selected recent studies and highlight how their results might help to define different processes and functions that are presumably carried out by the CA3 region, in particular regarding the seemingly opposing functions of pattern separation and pattern completion. We conclude with discussing limitations of functional imaging and briefly outline possible future developments of the field. The hippocampus is something of a lodestone for functional imaging studies in human memory research. However, in addition to methodological shortcomings inherent to functional magnetic resonance imaging fMRI such as the indirect relationship to neuronal activity and the relatively low signal-to-noise ratio SNR and significant susceptibility artifacts in this region Ojemann et al. Everything we know from in vitro and animal studies points in the opposite direction. Not only is the hippocampus histologically heterogeneous, but electrophysiological recordings in subfields of the rodent hippocampus suggest a functional dissociation, and circumscribed lesions produce dissociable deficits Lee and Kesner, a ; Lee et al. Some of the hippocampal subfields might even be involved in contrary operations, which could easily lead to null results or opposite conclusions across studies.

GABAergic connectivity is subject to prominent structural and molecular plasticity in relation ca3 hippocampus memory encoding. Bazelot, M. Chamberlain, S.

Federal government websites often end in. The site is secure. The hippocampus, in the temporal lobe, is phylogenetically one of the oldest parts of the brain and forms part of the limbic system. The hippocampus proper is defined by the dentate gyrus and Cornu Ammonis CA. The CA3 region has attracted major attention in recent years for its specific role in memory processes, susceptibility to seizures and neuro-degeneration. Internal connectivity in the CA3 subfield is more rich than in other hippocampal regions. This circuit is implicated in encoding spatial representations O'Keefe and Nadel, and episodic memories Scoville and Milner,

Thank you for visiting nature. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. To support cognitive function, the CA3 region of the hippocampus performs computations involving attractor dynamics. Understanding how cellular and ensemble activities of CA3 neurons enable computation is critical for elucidating the neural correlates of cognition. Moreover, the two neuron types have distinct morphological and physiological phenotypes and are differentially modulated by acetylcholine.

Ca3 hippocampus

The hippocampus, in the temporal lobe, is phylogenetically one of the oldest parts of the brain and forms part of the limbic system. The hippocampus proper is defined by the dentate gyrus and Cornu Ammonis CA. The CA3 region has attracted major attention in recent years for its specific role in memory processes, susceptibility to seizures and neuro-degeneration. Internal connectivity in the CA3 subfield is more rich than in other hippocampal regions. This circuit is implicated in encoding spatial representations O'Keefe and Nadel, and episodic memories Scoville and Milner, The CA3 region receives inputs from the entorhinal cortex either directly via the perforant path or indirectly from the dentate gyrus via the mossy fibers Amaral and Witter, The mossy fiber pathway acts as a high-pass filter that translates densely coded cortical signals to a sparse, specific hippocampal code, essential for memory formation. This e-book aims to highlight recent advances by bringing together experts on the cellular and molecular mechanisms regulating the wiring properties of the CA3 hippocampal microcircuit in both physiological and pathological conditions. The seven reviews and four research articles are organized to follow neuronal information flowing from the dentate gyrus to the CA3 associative network.

Tictactoy

Mutations in genes associated with neuronal migration in mouse models result in lamination defects of the CA3 area, a region especially vulnerable to stress and seizure-induced damage. En passant boutons From the French for 'passing' and 'button', swellings on an axon that make non-terminal synaptic contacts on another neuron. Tsukamoto, M. Nakashiba, T. Understanding memory through hippocampal remapping. By contrast, in healthy aged as compared to healthy young humans the perforant pathway which connects ERC and hippocampus is specifically degraded, and the degree of fiber loss is correlated with the degree of behavioral memory deficits Yassa et al. Ayala, G. Hippocampal CA3 output is crucial for ripple- associated reactivation and consolidation of memory. The result suggests that the NMDA receptor-dependent synaptic plasticity mechanisms in CA3 are critical to perform the pattern completion process in the hippocampus. Adult-born neurons are necessary for extended contextual discrimination. Sachidhanandam, S. In contrast, the CA3c field may support pattern separation via interactions with the DG. Contributions of the hippocampal subfields and entorhinal cortex to disambiguation during working memory.

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An enhanced release probability over several tens of milliseconds is ascribed to a residual elevation of intra-terminal Ca Holderith et al. The CA3a,b is also important for encoding of spatial information requiring multiple trials including the acquisition of arbitrary associations. Hippocampus 24 , — Neuron 90 , — Scott, R. Physiology and pharmacology of unitary synaptic connections between pairs of cells in areas CA3 and CA1 of rat hippocampal slice cultures. However, they were initially impaired in performing the task normally when the same task was carried out in a novel environment i. These two kinds of information may be projected to the CA3 region of the hippocampus via the medial and lateral perforant path to enable the organism to remember a particular object and its location. Nature : — In addition, neurophysiological and acetylcholinesterase and BDA an anterograde tracer results suggest that the output from dorsal CA3 to the medial septum via the fimbria was damaged without removing the input connections back to dorsal CA3a,b Hunsaker et al. Paradigms asking participants to differentiate between highly similar stimulus material provide a good model for the investigation of pattern separation processes, but they should be complemented by experiments which require participants to retrieve paired associates, which is another major function ascribed to CA3. To obtain the best experience, we recommend you use a more up to date browser or turn off compatibility mode in Internet Explorer. The BOLD response is a coarse signal when compared to single cell activity, both in time and in space.