“Dentate gyrus”的意思、由来-开放百科全书

The dentate gyrus is part of a brain region known as the hippocampus (part of the hippocampal formation). The dentate gyrus is thought to contribute to the formation of new episodic memories,^[1]^[1] the spontaneous exploration of novel environments,^[1] and other functions.^[2] It is notable as being one of a select few brain structures currently known to have significant rates of adult neurogenesis in many species of mammals, from rodents to primates ^[3] (other sites include the subventricular zone of the striatum^[4] and cerebellum^[5]). However, whether neurogenesis exists in the adult human dentate gyrus is currently a matter of debate.^[6]^[7]

Structure

The dentate gyrus (DG) consists of three distinct layers: molecular, granular, and polymorphic, and participates in the 'hippocampal circuit' or trisynaptic loop.^[8] The neurons of the granule cell layer are called granule cells project axons called mossy fibers to make excitatory synapses on the dendrites of CA3 pyramidal neurons. A second excitatory cell type in the DG, the mossy cell,^[9] projects its axons widely along the septotemporal axis, with the ipsilateral projection skipping the first 1–2 mm near the cell bodies,^[10] an unusual configuration, hypothesized to prepare a set of cell assemblies in CA3 for a data retrieval role, by randomizing their cell distribution.^[11] Granule cells of the DG receive excitatory input from the entorhinal cortex by way of the perforant pathway.^[12] This input is primarily made up of signals from layer II of the entorhinal cortex, and the dentate gyrus receives no direct inputs from other cortical structures.^[13] The perforant pathway is divided into the medial and lateral perforant paths, 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 their distal dendrites. Most lateral views of the dentate gyrus may appear to suggest a structure consisting of just one entity, but medial movement may provide evidence of the ventral and dorsal parts of the dentate gyrus.^[14]

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.^[15] 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 adulthood.^[16]^[17] The germinal sources of granule cells and their migration pathways ^[18]^[19] have been studied 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 then 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 that point on. The newly generated granule cells accumulate under the older cells that began to settle in the granular layer. As more granule cells are produced, the layer thickens and the cells are stacked up according to age - the oldest being the most superficial and the youngest being deeper.^[20] The granule cell precursors remain in a subgranular zone that becomes progressively thinner as the dentate gyrus grows, but these precursor cells are retained in adult rats. These sparsely scattered cells constantly generate granule cell neurons,^[21]^[22] which add to the total population. There are a variety of other differences in the rat, monkey and human dentate gyrus. The granule cells only have apical dendrites in the rat. But in the monkey and human, many granule cells also have basal dendrites.^[23]

Function

The dentate gyrus is thought to contribute to the formation of memories, and to play a role in depression.

Memory

The role of the hippocampus in learning and memory has been studied for many decades since early lesion studies. One of the most prominent early cases of anterograde amnesia (inability to form new memories) linking the hippocampus to memory formation was the case of Henry Molaison (anonymously known as Patient H.M. until his death in 2008).^[25] His epilepsy was treated with surgical removal of his hippocampi (left and right hemispheres each have their own hippocampus) as well as some surrounding tissue. This targeted brain tissue removal left Mr. Molaison with an inability to form new memories, and the hippocampus has been thought critical to memory formation since that time.^[25] It remains unclear how the hippocampus enables new memory formation, but one process, called long term potentiation (LTP), occurs in this brain region.^[25] LTP involves long-lasting strengthening of synaptic connections after repeated stimulation.^[12] While the dentate gyrus shows LTP, it is also one of the few regions of the adult mammalian brain where neurogenesis (i.e., the birth of new neurons) takes place. Some studies hypothesize that new memories could preferentially use newly formed dentate gyrus cells, providing a potential mechanism for distinguishing multiple instances of similar events or multiple visits to the same location.^[26] This increased neurogenesis is associated with improved spatial memory in rodents, as seen through performance in a maze.^[27]

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.^[28] 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.^[29] Both endogenous and exogenous glucocorticoids are known to cause psychosis and depression,^[30] implying that neurogenesis in the dentate gyrus may play an important role in modulating symptoms of stress and depression.^[31]

Other

Some evidence suggests neurogenesis in the dentate gyrus increases in response to aerobic exercise.^[32] Several experiments have shown neurogenesis (the development of nerve tissues) often increases in the dentate gyrus of adult rodents when they are exposed to an enriched environment.^[33]^[34]

The dentate gyrus is also known to serve as a pre-processing unit. When information enters, it is known to separate very similar information into distinct and unique details. This prepares the relevant data for storage in the hippocampal CA3 section.^[35]

Spatial behavior

Studies have shown that after destroying about 90% of their dentate gyrus (dg) cells, rats had extreme difficulty in maneuvering through a maze they had been through, prior to the lesion being made. When being tested a number of times to see whether they could learn a maze, the results showed that the rats did not improve at all, indicating that their working memories were severely impaired. Rats had trouble with place strategies because they could not consolidate learned information about a maze into their working memory, and, thus, could not remember it when maneuvering through the same maze in a later trial. Every time a rat entered the maze, the rat behaved as if it was seeing the maze for the first time.^[36]

Blood sugar

Studies by researchers at Columbia University Medical Center indicate poor glucose control can lead to deleterious effects on the dentate gyrus.^[37]

References

1. ^¹{{Cite journal|vauthors=Saab BJ, Georgiou J, Nath A, Lee FJ, Wang M, Michalon A, Liu F, Mansuy IM, Roder JC | title = NCS-1 in the dentate gyrus promotes exploration, synaptic plasticity, and rapid acquisition of spatial memory. | journal = Neuron | volume = 63 | issue = 5 | pages = 643–56 | year = 2009 | pmid = 19755107 | doi = 10.1016/j.neuron.2009.08.014 }}
2. ^{{Cite journal| editor = Helen Scharfman | title = The Dentate Gyrus: A comprehensive guide to structure, function, and clinical implications | journal = Progress in Brain Research | volume = 163 | pages = 1–840 | year = 2007}}
3. ^{{cite journal | vauthors = Cameron HA, McKay RD | title = Adult neurogenesis produces a large pool of new granule cells in the dentate gyrus | journal = J. Comp. Neurol. | volume = 435 | issue = 4 | pages = 406–17 | date = July 2001 | pmid = 11406822 | doi = 10.1002/cne.1040}}
4. ^{{cite journal|last1=Ernst|first1=A|last2=Alkass|first2=K|last3=Bernard|first3=S|last4=Salehpour|first4=M|last5=Perl|first5=S|last6=Tisdale|first6=J|last7=Possnert|first7=G|last8=Druid|first8=H|last9=Frisén|first9=J|title=Neurogenesis in the striatum of the adult human brain.|journal=Cell|date=27 February 2014|volume=156|issue=5|pages=1072–83|doi=10.1016/j.cell.2014.01.044|pmid=24561062}}
5. ^{{cite journal |vauthors=Ponti G, Peretto P, Bonfanti L |title=Genesis of neuronal and glial progenitors in the cerebellar cortex of peripuberal and adult rabbits |journal=PLoS ONE |volume=3 |issue=6 |pages=e2366 |year=2008 |pmid=18523645 |pmc=2396292 |doi=10.1371/journal.pone.0002366|bibcode=2008PLoSO...3.2366P }}
6. ^{{cite journal | vauthors = Sorrells SF, Paredes MF, Cebrian-Silla A, Sandoval K, Qi D, Kelley KW, James D, Mayer S, Chang J, Auguste KI, Chang EF, Gutierrez AJ, Kriegstein AR, Mathern GW, Oldham MC, Huang EJ, Garcia-Verdugo JM, Yang Z, Alvarez-Buylla A |display-authors = 6| title = Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults | journal = Nature | volume = 555 | issue = 7696 | pages = 377–381 | date = March 2018 | pmid = 29513649 | pmc = 6179355 | doi = 10.1038/nature25975 | bibcode=2018Natur.555..377S}}
7. ^{{cite journal | vauthors = Boldrini M, Fulmore CA, Tartt AN, Simeon LR, Pavlova I, Poposka V, Rosoklija GB, Stankov A, Arango V, Dwork AJ, Hen R, Mann JJ|display-authors = 6 | title = Human Hippocampal Neurogenesis Persists throughout Aging | journal = Cell Stem Cell | volume = 22 | issue = 4 | pages = 589–599.e5 | date = April 2018 | pmid = 29625071 |pmc = 5957089 | doi = 10.1016/j.stem.2018.03.015 }}
8. ^{{Cite book|author=A. Treves|author2=A. Tashiro|author3=M.P. Witter|author4=E.I. Moser |title=What is the mammalian dentate gyrus good for? |edition= 154th|issue=4|year=2008 |pages=1155–1172}}
9. ^Scharfman, H. E. (July 2016) “The enigmatic mossy cell of the dentate gyrus” Nature Reviews Neuroscience 17(9):562-575, DOI:10.1038/nrn.2016.87, PMCID:pmc5369357
10. ^Amaral, D. G. and Witter, M. P. (1989) “The three-dimensional organization of the hippocampal formation: a review of anatomical data.” Neuroscience 31(3): 571-591. DOI: 10.1016/0306-4522(89)90424-7, {{PMID|2687721}}
11. ^Legéndy, C. R. (April 2017) "On the 'data stirring' role of the dentate gyrus of the hippocampus". Reviews in the Neurosciences 28 (6): 599-615. DOI: 10.1515/revneuro-2016-0080.
12. ^¹{{cite book|last1=Blumenfeld|first1=Hal|title=Neuroanatomy through clinical cases|date=2010|publisher=Sinauer Associates|location=Sunderland, Mass.|isbn=978-0878936137|edition= 2nd}}
13. ^{{Cite book|author=Nolte, John |title=The Human Brain: An Introduction to Its Functional Neuroanatomy |edition= fifth|year=2002 |pages=570–573}}
14. ^{{cite journal|author1=Rachel A. Dalley |author2=Lydia L. Ng |author3=Angela L. Guillozet-Bongaarts |journal=Nature Precedings|title=Dentate Gyrus|doi=10.1038/npre.2008.2095.1|year=2008 }}
15. ^{{cite journal | vauthors = Bayer SA, Altman J | title = Hippocampal development in the rat: cytogenesis and morphogenesis examined with autoradiography and low-level X-irradiation | journal = J. Comp. Neurol. | volume = 158 | issue = 1 | pages = 55–79 | date = November 1974 | pmid = 4430737 | doi = 10.1002/cne.901580105 }}
16. ^{{Cite book| vauthors = Bayer SA, Altman J | title = The Human Brain During The Early First Trimester | volume = 5 Atlas of Human Central Nervous System Development | year = 2008|at = Appendix, p. 497}}
17. ^{{Cite journal |vauthors=Eriksson PS, Perfilieva E, Björk-Eriksson T, etal |title=Neurogenesis in the adult human hippocampus |journal=Nat. Med. |volume=4 |issue=11 |pages=1313–7 |date=November 1998 |pmid=9809557 |doi=10.1038/3305 |url=}}
18. ^{{cite journal | vauthors = Altman J, Bayer SA | title = Migration and distribution of two populations of hippocampal granule cell precursors during the perinatal and postnatal periods | journal = J. Comp. Neurol. | volume = 301 | issue = 3 | pages = 365–81 | date = November 1990 | pmid = 2262596 | doi = 10.1002/cne.903010304 }}
19. ^{{cite journal | vauthors = Altman J, Bayer SA | title = Mosaic organization of the hippocampal neuroepithelium and the multiple germinal sources of dentate granule cells | journal = J. Comp. Neurol. | volume = 301 | issue = 3 | pages = 325–42 | date = November 1990 | pmid = 2262594 | doi = 10.1002/cne.903010302 }}
20. ^{{cite journal | vauthors = Angevine JB | title = Time of neuron origin in the hippocampal region. An autoradiographic study in the mouse | journal = Exp Neurol Suppl | volume = | issue =Suppl 2 | pages = Suppl 2:1–70 | date = October 1965 | pmid = 5838955 }}
21. ^{{cite journal | vauthors = Bayer SA, Yackel JW, Puri PS | title = Neurons in the rat dentate gyrus granular layer substantially increase during juvenile and adult life | journal = Science | volume = 216 | issue = 4548 | pages = 890–2 | date = May 1982 | pmid = 7079742 |bibcode = 1982Sci...216..890B |doi = 10.1126/science.7079742 }}
22. ^{{cite journal | vauthors = Bayer SA | title = Changes in the total number of dentate granule cells in juvenile and adult rats: a correlated volumetric and 3H-thymidine autoradiographic study | journal = Exp Brain Res | volume = 46 | issue = 3 | pages = 315–23 | date = 1982 | pmid = 7095040 | doi = 10.1007/bf00238626}}
23. ^¹{{cite journal | vauthors = Amaral DG, Scharfman HE, Lavenex P | title = The dentate gyrus: fundamental neuroanatomical organization (dentate gyrus for dummies) | journal = Progress in Brain Research | volume = 163 | issue = | pages = 3–22 | date = 2007 | pmid = 17765709 | pmc = 2492885 | doi = 10.1016/S0079-6123(07)63001-5| isbn = 9780444530158 }}
24. ^{{Cite journal|vauthors=Faiz M, Acarin L, Castellano B, Gonzalez B |title=Proliferation dynamics of germinative zone cells in the intact and excitotoxically lesioned postnatal rat brain |journal=BMC Neurosci |volume=6 |issue= 1|page=26 |year=2005 |pmid=15826306 |pmc=1087489 |doi=10.1186/1471-2202-6-26 }}
25. ^¹²{{cite book|vauthors = Kandel ER, Schwartz J, Jessell T, Siegelbaum S, Hudspeth AJ|title=Principles of neural science|date=2013|publisher=McGraw Hill Professional|isbn=978-0-07-139011-8|edition= 5th}}
26. ^{{cite journal | vauthors = Nakashiba T, Cushman JD, Pelkey KA, Renaudineau S, Buhl DL, McHugh TJ, Rodriguez Barrera V, Chittajallu R, Iwamoto KS, McBain CJ, Fanselow MS, Tonegawa S |display-authors = 6 | title = Young dentate granule cells mediate pattern separation, whereas old granule cells facilitate pattern completion | journal = Cell | volume = 149 | issue = 1 | pages = 188–201 | date = March 2012 | pmid = 22365813 | pmc = 3319279 | doi = 10.1016/j.cell.2012.01.046 }}
27. ^{{cite web |url=http://www.ars.usda.gov/is/ar/archive/aug07/aging0807.htm. |title="Food and the Aging Mind". First in a Series: Nutrition and Brain Function |vauthors=Bliss RM|date=August 2007 |website=USDA |publisher=USDA.gov |access-date= February 27, 2010}}
28. ^{{cite journal | vauthors = Malberg JE, Eisch AJ, Nestler EJ, Duman RS | title = Chronic antidepressant treatment increases neurogenesis in adult rat hippocampus | journal = J. Neurosci. | volume = 20 | issue = 24 | pages = 9104–10 | date = December 2000 | pmid = 11124987}}
29. ^{{cite journal | vauthors = Gould E, Tanapat P, McEwen BS, Flügge G, Fuchs E | title = Proliferation of granule cell precursors in the dentate gyrus of adult monkeys is diminished by stress | journal = Proc. Natl. Acad. Sci. U.S.A. | volume = 95 | issue = 6 | pages = 3168–71 | date = March 1998 | pmid = 9501234 | pmc = 19713 | doi = 10.1073/pnas.95.6.3168| bibcode = 1998PNAS...95.3168G}}
30. ^{{cite journal | vauthors = Jacobs BL, van Praag H, Gage FH | title = Adult brain neurogenesis and psychiatry: a novel theory of depression | journal = Mol. Psychiatry | volume = 5 | issue = 3 | pages = 262–9 | date = May 2000 | pmid = 10889528 | doi = 10.1038/sj.mp.4000712}}
31. ^{{cite journal | vauthors = Surget A, Tanti A, Leonardo ED, Laugeray A, Rainer Q, Touma C, Palme R, Griebel G, Ibarguen-Vargas Y, Hen R, Belzung C | title = Antidepressants recruit new neurons to improve stress response regulation | journal = Mol. Psychiatry | volume = 16 | issue = 12 | pages = 1177–88 | date = December 2011 | pmid = 21537331 | pmc = 3223314 | doi = 10.1038/mp.2011.48 }}
32. ^{{cite journal|last=Praag|first=H|year=1999|title=Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus|journal=Nature Neuroscience|volume=2|pages=266–270|doi=10.1038/6368|pmid=10195220|issue=3}}
33. ^{{cite journal | vauthors = Kempermann G, Kuhn HG, Gage FH | title = More hippocampal neurons in adult mice living in an enriched environment | journal = Nature | volume = 386 | issue = 6624 | pages = 493–5 | date = April 1997 | pmid = 9087407 | doi = 10.1038/386493a0 |bibcode = 1997Natur.386..493K }}
34. ^{{cite journal | vauthors = Eadie BD, Redila VA, Christie BR | title = Voluntary exercise alters the cytoarchitecture of the adult dentate gyrus by increasing cellular proliferation, dendritic complexity, and spine density | journal = J. Comp. Neurol. | volume = 486 | issue = 1 | pages = 39–47 | date = May 2005 | pmid = 15834963 | doi = 10.1002/cne.20493 }}
35. ^{{cite web | url=http://www.frontiersin.org/Neural_Circuits/researchtopics/Structure_function_and_plastic/737 | title=Structure, function, and plasticity of hippocampal dentate gyrus microcircuits | Frontiers Research Topic}}
36. ^{{cite journal | vauthors = Xavier GF, Costa VC | title = Dentate gyrus and spatial behaviour | journal = Prog. Neuropsychopharmacol. Biol. Psychiatry | volume = 33 | issue = 5 | pages = 762–73 | date = August 2009 | pmid = 19375476 | doi = 10.1016/j.pnpbp.2009.03.036 }}
37. ^{{cite news|url=https://www.nytimes.com/2009/01/01/health/31memory.html?_r=1&em=&pagewanted=print|title=Blood Sugar Control Linked to Memory Decline, Study Says |publisher=Nytimes.com |date= 1 January 2009|accessdate=2011-03-13}}