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Perforant path

Field	Value
Name	Perforant path
Latin	tractus perforans
Image	HippocampalRegions.jpg
Caption	Diagram of hippocampal regions. DG: Dentate gyrus. Perforant path not labeled, but would arise from the right.

In the brain, the perforant path or perforant pathway provides a connectional route from the entorhinal cortex to all fields of the hippocampal formation, including the dentate gyrus, all CA fields (including CA1), and the subiculum.

Though it arises mainly from entorhinal layers II and III, the perforant path comprises a smaller component that originates in deep layers V and VI. There is a major dichotomy with respect to the laminar origin and related terminal distribution: neurons in layer II (and possibly layer VI) project to the dentate gyrus and CA3, whereas layer III (and possibly layer V) cells project to CA1 and the subiculum via the temporoammonic pathway.

In addition to playing a role in spatial memory learning generally, the temporoammonic branch (TA-CA1) of the perforant path mediates spatial memory consolidation. The temporoammonic pathway has also been implicated in stress-based animal models of depression.

It may also play a role in temporal lobe seizures.

In rats

In rats, pyramidal and stellate cells in layer II of entorhinal cortex project through the subiculum of the hippocampus, giving rise to the name "perforant pathway". These glutamatergic fibers form a laminar pattern and terminate in the dentate gyrus and cornu ammonis 3 (CA3) region of the hippocampus. Fibers arising in the lateral portions of the entorhinal cortex show enkephalin immunoreactivity, whereas medial portions appear to contain cholecystokinin. Additionally, pyramidal cells in layer III of the entorhinal cortex send topographic projections along the perforant pathway which branch into the subiculum and CA1.

In mice

In mice, the projection to CA1, and the subiculum all come primarily from EC layer III.

According to Suh et al. (2011 Science 334:1415) the projection to CA3 and dentate gyrus in mice is primarily from layer II of entorhinal cortex, and forms a trisynaptic path with hippocampus (dentate gyrus to CA3 to CA1), distinguished from the direct (monosynaptic) perforant path from Layer III of entorhinal cortex to CA1 and subiculum.

References

Shepherd, GM. The Synaptic Organization of the Brain. New York: Oxford University Press. 1998.

References

(2000). "Cortico-hippocampal communication by way of parallel parahippocampal-subicular pathways". Hippocampus.
(2008). "Disruption of the direct perforant path input to the CA1 subregion of the dorsal hippocampus interferes with spatial working memory and novelty detection". Behavioural Brain Research.
(2004). "Role for a cortical input to hippocampal area CA1 in the consolidation of a long-term memory". Nature.
(2013). "Chronic Stress Induces a Selective Decrease in AMPA Receptor-Mediated Synaptic Excitation at Hippocampal Temporoammonic-CA1 Synapses". Journal of Neuroscience.
(2005). "Epileptogenesis is Associated with Enhanced Glutamatergic Transmission in the Perforant Path". Journal of Neurophysiology.
(1 October 1976). "Cells of origin of entorhinal cortical afferents to the hippocampus and fascia dentata of the rat.". The Journal of Comparative Neurology.

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This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

hippocampus-(brain)

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