Ca3 hippocampus

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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.

Ca3 hippocampus

From a behavioral perspective, the CA3a,b subregion of the hippocampus plays an important role in the encoding of new spatial information within short-term memory with a duration of seconds and minutes. This can easily be observed in tasks that require rapid encoding, novelty detection, one-trial short-term or working memory, and one-trial cued recall primarily for spatial information. These are tasks that have been assumed to reflect the operations of episodic memory and require interactions between CA3a,b and the dentate gyrus via mossy fiber inputs into the CA3a,b. The CA3a,b is also important for encoding of spatial information requiring multiple trials including the acquisition of arbitrary and relational associations. These tasks tend to be non-episodic and can be mediated by arbitrary and conjunctive operations. All these tasks are assumed to operate within an autoassociative network function of the CA3 region. The output from CA3a,b via the fimbria and the medial and lateral perforant path inputs play a supporting role in the neural circuit that supports the operation of these tasks. The CA3a,b also supports retrieval of short-term memory information based on a spatial pattern completion process. Finally, CA3c may, in cooperation with the dentate gyrus, serve an important role in processing the geometry of the environment. This review article emphasizes the importance of behavioral functions of the CA3 subregion of the hippocampus. In the first section, I present a general overview of the anatomy of the hippocampus. In the second section, I present the influence of an autoassociative network function of the CA3 region in supporting mnemonic functions. In general terms, the data suggest that CA3a,b mediates the acquisition and encoding of spatial information within short-term memory with a duration of seconds and minutes. In the context of short-term memory, the CA3a,b mediates rapid encoding of especially spatial information, novelty detection, and one-trial cued recall all forms of episodic memory. Also, CA3a,b mediates encoding of information requiring multiple trials to construct relational representations.

Fernandes, H. Attractor dynamics of spatially correlated neural activity in the limbic system. Armstrong, J.

The hippocampus proper refers to the actual structure of the hippocampus which is made up of three regions or subfields. There are four hippocampal subfields , regions in the hippocampus proper which form a neural circuit called the trisynaptic circuit. CA1 is the first region in the hippocampal circuit, from which a major output pathway goes to layer V of the entorhinal cortex. Another significant output is to the subiculum. It receives some input from layer II of the entorhinal cortex via the perforant path. Its pyramidal cells are more like those in CA3 than those in CA1.

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.

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,

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Electrical coupling underlies high-frequency oscillations in the hippocampus in vitro. Re-activating the sparse granule cell ensemble optically later, induced a fear response in a different context. In humans, especially with fMRI imaging, these problems increase further. Interneuron diversity series: containing the detonation — feedforward inhibition in the CA3 hippocampus. Tronel, S. They include Schaffer collaterals that project to CA1 as well as those that ramify within the CA3 region. Estimates of connectivity are somewhat higher from paired records in slices of sensory cortex. This hyperactivity could be a sign for a computational shift from pattern separation to pattern completion Yassa et al. Work combining somatic records and synaptic stimuli with cell-attached records from dendrites, showed the activation of both inward currents, probably persistent Na channels, low-threshold Ca channels Magee and Johnston, , and outward currents, both inactivating and persistent Hoffman et al. Hoffman, D. Mizumori, S. References Amaral D. A specific role for recurrent synapses was established by genetically deleting NMDA receptor expression at recurrent synapses of CA3 pyramidal cells Nakazawa et al.

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Distinct ensemble codes in hippocampal areas CA3 and CA1. The studies described thus far used classical univariate approaches to data analysis, investigating whether BOLD activity systematically differs between conditions, usually modeled within the general linear model GLM framework. Lacy et al. Rate remapping refers to an alteration in the firing rates of place cells that retain place fields in the same locations as before. A double dissociation between hippocampal subfields: differential time course of CA3 and CA1 place cells for processing changed environments. Finally, CA3a,b may, in cooperation with the dentate gyrus, play an important role in processing the geometry of the environment. A closer look at the experimental literature on human hippocampal subfield functions reveals a gap between these elaborate theoretical and computational models and electrophysiological results on the one hand and what has actually been confirmed in studies in humans on the other. Nakazawa, K. Psychology, Univ. Cellular bases of hippocampal EEG in the behaving rat. In this review, we first summarize selected fMRI studies that aimed to differentiate between hippocampal subregions in healthy participants. Performance-related sustained and anticipatory activity in human medial temporal lobe during delayed match-to-sample. Dendritically expressed inactivating K-channels have been linked to less-than-linear summation of paired EPSPs impinging on different dendrites Urban and Barrionuevo,