Dentate gyrus: Difference between revisions
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== References == |
== References == |
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{{Reflist}} Bayer, SA, and J Altman Hippocampal development in the rat: Cytogenesis and morphogenesis examined with autoradiagraphy and low-level X-irradiation. Journal of Comparative Neurology, Volume 158:55-80, 1974. |
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== External links == |
== External links == |
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Revision as of 19:01, 10 September 2010
| Dentate gyrus | |
|---|---|
 Diagram of hippocampal regions. DG: Dentate gyrus. | |
 Coronal section of brain immediately in front of pons. (Label for "Gyrus dentatus" is at bottom left.) | |
| Details | |
| Part of | Temporal lobe |
| Artery | Posterior cerebral Anterior choroidal |
| Identifiers | |
| Latin | gyrus dentatus |
| MeSH | D018891 |
| NeuroNames | 179 |
| NeuroLex ID | birnlex_1178 |
| TA98 | A14.1.09.237 A14.1.09.339 |
| TA2 | 5521 |
| FMA | 61922 |
| Anatomical terms of neuroanatomy | |
The dentate gyrus is part of the hippocampal formation. It is thought to contribute to new memories as well as other functional roles.[1][2] It is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult humans,[3] (other sites include the olfactory bulb and cerebellum).[4][5]
Structure
The dentate gyrus consists of three layers of neurons: molecular, granular, and polymorphic. The middle layer is most prominent and contains granule cells that project to the CA3 subfield of the hippocampus.[6] These granule cells project mostly to interneurons, but also to pyramidal cells and are the principal excitatory neurons of the dentate gyrus. The major input to the dentate gyrus (the so-called perforant pathway) is from layer 2 of the entorhinal cortex, and the dentate gyrus receives no direct inputs from other cortical structures. The perforant pathway is divided into the medial perforant path and the lateral perforant path, generated, respectively, at the medial and lateral portions of the entorhinal cortex. The medial perforant path synapses onto the proximal dendritic area of the granule cells, whereas the lateral perforant path does so onto the distal dendrites of these same cells.
Development
The granule cells in the dentate gyrus are distinguished by their late time of formation during brain development. In rats, approximately 85% of the granule cells are generated after birth (Bayer and Altman, 1974). In humans, it is estimated that granule cells begin to be generated during gestation weeks 10.5 to 11, and continue being generated during the second and third trimesters, after birth and all the way into the adult period (Bayer and Altman,2008). Altman and Bayer (1990) have studied the germinal sources of granule cells during rat brain development. The oldest granule cells are generated in a specific region of the hippocampal neuroepithelium and migrate into the primordial dentate gyrus around embryonic days (E)17/18 and settle as the outermost cells in the forming granular layer. Next, dentate precursor cells move out of this same area of the hippocampal neuroepithelium and, retaining their mitotic capacity, invade the hilus (core) of the forming dentate gyrus. This dispersed germinal matrix is the source of granule cells from now on. The newly generated granule cells accumulate under the older cells that began to settle in the granular layer. As more and more granule cells are produced, the layer thickens, and the cells are stacked up according to age--the oldest are most superficial and the youngest are deep. The granule cell precursors remain in a subgranular zone that becomes progressively thinner as the dentate gyrus grows, but it is retained in adults as sparsely scattered cells that constantly generate granule cell neurons. Bayer et al.(1982) showed that the new granule cells in rats add to the total population, so the granule cells in the dentate gyrus are the only known population of neurons in the brain that are constantly increasing their numbers.
Function
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The dentate gyrus is thought to contribute to the formation of memories and to play a role in depression.
Memory
The dentate gyrus is one of the few regions of the adult brain where neurogenesis (i.e., the birth of new neurons) takes place. Neurogenesis is thought to play a role in the formation of new memories. New memories could preferentially utilize newly-formed dentate gyrus cell, providing a potential mechanism for distinguishing multiple instances of similar events or multiple visits to the same location.[citation needed] A Study at the Human Nutrition Research Center on Aging showed that feeding blueberry extract to older rats for a short time frame increases neurogenesis in the dentate gyrus. This increased neurogenesis is associated with improved spatial memory, as seen through performance in a maze.[8]
Stress and Depression
The dentate gyrus may also have a functional role in stress and depression. For instance, neurogenesis has been found to increase in response to chronic treatment with antidepressants[9]. On the contrary, however, the physiological effects of stress, often characterized by release of glucocorticoids such as cortisol, as well as activation of the sympathetic division of the autonomic nervous system, have been shown to inhibit the process of neurogenesis in primates[10]. Both endogenous and exogenous glucocorticoids are known to cause psychosis and depression,[11], implying that neurogenesis in the dentate gyrus may play an important role in modulating symptoms of stress and depression.
Other
Some evidence suggests that neurogenesis in the dentate gyrus increases in response to aerobic exercise[12].
Blood Sugar
Studies by researchers at Columbia University Medical Center indicate that poor glucose control can lead to deleterious effects on the dentate gyrus.[13]
References
- ^ Helen Scharfman, ed. (2007). The Dentate Gyrus: A comprehensive guide to structure, function, and clinical imiplications. Vol. 163. pp. 1–840.
{{cite book}}:|journal=ignored (help) - ^ Saab BJ, Georgiou J, Nath A, Lee FJ, Wang M, Michalon A, Liu F, Mansuy IM, Roder JC. (2009). "NCS-1 in the dentate gyrus promotes exploration, synaptic plasticity, and rapid acquisition of spatial memory". Neuron. 63 (5): 643–56. doi:10.1016/j.neuron.2009.08.014. PMID 19755107.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Cameron HA, McKay RD (2001). "Adult neurogenesis produces a large pool of new granule cells in the dentate gyrus". J Comp Neurol. 435 (4): 406–17. doi:10.1002/cne.1040. PMID 11406822.
- ^ Graziadei PP, Monti Graziadei GA (1985). "Neurogenesis and plasticity of the olfactory sensory neurons". PLoS ONE. 457: 127–42. PMID 3913359.
- ^ Ponti G, Peretto B, Bonfanti L (2008). "Genesis of neuronal and glial progenitors in the cerebellar cortex of peripuberal and adult rabbits". PLoS ONE. 3 (6): e2366. doi:10.1371/journal.pone.0002366. PMC 2396292. PMID 18523645.
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ Nolte, John (2002). The Human Brain: An Introduction to Its Functional Neuroanatomy (fifth ed.). pp. 570–573.
- ^ Faiz M, Acarin L, Castellano B, Gonzalez B (2005). "Proliferation dynamics of germinative zone cells in the intact and excitotoxically lesioned postnatal rat brain". BMC Neurosci. 6: 26. doi:10.1186/1471-2202-6-26. PMC 1087489. PMID 15826306.
{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: unflagged free DOI (link) - ^ Bliss, Rosalie Marion. “Food and the Aging Mind”. First in a Series: Nutrition and Brain Function. http://www.ars.usda.gov/is/ar/archive/aug07/aging0807.htm. (27 February 2010)
- ^ Malberg JE, Eisch AJ, Nestler EJ, Duman RS (2000). "Chronic antidepressant treatment increases neurogenesis in adult rat hippocampus". J. Neurosci. 20 (24): 9104–9110. PMID 11124987.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Gould E, Tanapat P, McEwen BS, Flugge G, Fuchs E (1998). "Proliferation of granule cell precursors in the dentate gyrus of adult monkeys is diminished by stress". PNAS. 95 (6): 3168–3171. doi:10.1073/pnas.95.6.3168. PMC 19713. PMID 9501234.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Jacobs B, Praag H, Gage F (2000). "Adult brain neurogenesis and psychiatry: a novel theory of depression". Mol. Psychiatry. 5 (3): 262–9. doi:10.1038/sj.mp.4000712. PMID 10889528.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Kempermann G, Kuhn HG, Gage FH, (1997). "More hippocampal neurons in adult mice living in an enriched environment". Nature. 386 (6624): 493–495. doi:10.1038/386493a0. PMID 9087407.
{{cite journal}}: CS1 maint: extra punctuation (link) CS1 maint: multiple names: authors list (link) - ^ http://www.nytimes.com/2009/01/01/health/31memory.html?_r=1&em=&pagewanted=print Blood Sugar Control Linked to Memory Decline, Study Says
Bayer, SA, and J Altman Hippocampal development in the rat: Cytogenesis and morphogenesis examined with autoradiagraphy and low-level X-irradiation. Journal of Comparative Neurology, Volume 158:55-80, 1974.
External links
- Slide at psycheducation.org
- Stained brain slice images which include the "Dentate gyrus" at the BrainMaps project
- "Dentate Gyrus NMDA Receptors Mediate Rapid Pattern Separation in the Hippocampal Network". Science 7 June 2007 DOI: 10.1126/science.1140263 - The source of déjà vu
- NIF Search - Dentate Gyrus via the Neuroscience Information Framework