Ca3 hippocampus

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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,

Ca3 hippocampus

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. It is often ignored due to its small size. CA3 receives input from the mossy fibers of the granule cells in the dentate gyrus , and also from cells in the entorhinal cortex via the perforant path. The mossy fiber pathway ends in the stratum lucidum. The perforant path passes through the stratum lacunosum and ends in the stratum moleculare. There are also inputs from the medial septum and from the diagonal band of Broca which terminate in the stratum radiatum, along with commisural connections from the other side of the hippocampus. The pyramidal cells in CA3 have a unique type of dendritic spine called a thorny excrescence or thorn, only found in CA3 pyramidal cells and hilar mossy cells. The thorn has a thin single spine with a number of heads. Clusters of thorns sit on a dendrite on a broad stem. There are also longer spines called long-neck spines.

Multi-vesicular release following a single action potential is most convincingly demonstrated when two distinct post-synaptic events can be resolved in time, as ca3 hippocampus some inhibitory synapses in the cerebellum Auger et al, ca3 hippocampus. Excitation of inhibitory cells by single CA3 pyramidal cells in the guinea pig hippocampus in vitro.

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.

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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.

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Fernandes, H. The site is secure. Kesner, in prep. Additional support comes from the finding that in a similar one-trial object—place learning followed by recall of the spatial position in which to respond when shown the object, Rolls et al. Gilbert, C. Ca changes induced in local recurrent terminals by pyramidal cell firing have been resolved by imaging Holderith et al. The pivotal role of the CA3 region in humans is discussed by Deuker et al. Hippocampal CA3 output is crucial for ripple-associated reactivation and consolidation of memory. When the task prolonged the delay significantly exceeding the short-term range e. The CA3a,b subregion of the hippocampus also appears to be necessary in some tasks that require multiple trials to acquire the task. The rats were then tested in the acquisition of a non-match to sample one-trial spatial location task on an eight-arm maze with sec delays. After 7. Organization of intrahippocampal projections originating from CA3 pyramidal cells in the rat. Neuroimage 44 — Herzog, E.

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Two loci of expression for long-term depression at hippocampal mossy fiber-interneuron synapses. Recurrent connections between CA3 cells in the hippocampus can be seen in early drawings of Golgi stained neurons. Kesner Dept. Doeller , 2 Juergen Fell , 1 and Nikolai Axmacher 1, 3. Certainly, recurrent terminals express various types of K channel which control transmitter release by limiting terminal depolarization. They describe how the shape of mossy fiber terminals affects transmission to both CA3 pyramidal cells and interneurons. The field will also benefit from studies that look at healthy young populations who have a genetic risk for developing AD such as carriers of the epsilon4 subtype of the apolipoprotein E gene Corder et al. Morris, R. Neuron 22 : — Neuron 65 7—19 Debanne, D. Connectivity in the associative recurrent CA3 network seems to be spatially more extensive and sparse than in other sensory cortices possibly facilitating representation coding. In the first section, I present a general overview of the anatomy of the hippocampus.