Parahippocampal gyrus

{{short description|Grey matter region surrounding the hippocampus}} {{Infobox anatomy | Name = Parahippocampal gyrus | Latin = gyrus parahippocampalis | Image = Sobo 1909 630 - Parahippocampal gyrus.png | Caption = Human brain seen from below. Parahippocampal gyrus shown in blue | Image2 = Cerebral Gyri - Medial Surface2.png | Caption2 = Medial view of left cerebral hemisphere. Parahippocampal gyrus shown in orange. | System = | Precursor = }} The '''parahippocampal gyrus''' (or '''hippocampal gyrus'''''<ref>Reuter P.: ''Der Grobe Reuter Springer Universalworterbuch Medizin, Pharmakologie Und Zahnmedizin: Englisch-deutsch (Band 2)'', Birkhäuser, 2005, {{ISBN|3-540-25102-2}}, p. 648 [https://books.google.com/books?id=fbSwyFld8PYC&dq=%22Gyrus+parahippocampalis%22&pg=PA648 here online]</ref>'') is a grey matter cortical region, a gyrus of the brain that surrounds the hippocampus and is part of the limbic system. The region plays an important role in memory encoding and retrieval. It has been involved in some cases of hippocampal sclerosis.<ref name="pmid14595469">{{cite journal |vauthors=Ferreira NF, de Oliveira V, Amaral L, Mendonça R, Lima SS |title=Analysis of parahippocampal gyrus in 115 patients with hippocampal sclerosis |journal=Arq Neuropsiquiatr |volume=61 |issue=3B |pages=707–11 |date=September 2003 |pmid=14595469 |doi= 10.1590/s0004-282x2003000500001|doi-access=free }}</ref> Asymmetry has been observed in schizophrenia.<ref name="pmid10618011">{{cite journal |vauthors=McDonald B, Highley JR, Walker MA, etal |title=Anomalous asymmetry of fusiform and parahippocampal gyrus gray matter in schizophrenia: A postmortem study |journal=Am J Psychiatry |volume=157 |issue=1 |pages=40–7 |date=January 2000 |pmid=10618011 |doi=10.1176/ajp.157.1.40 |s2cid=5915984 }}</ref>

==Structure== The anterior part of the gyrus includes the perirhinal and entorhinal cortices{{Citation needed|date=December 2009}}.

The term '''parahippocampal cortex''' is used to refer to an area that encompasses both the posterior parahippocampal gyrus and the medial portion of the fusiform gyrus{{Citation needed|date=March 2022}}.

==Function==

===Scene recognition=== The '''parahippocampal place area''' ('''PPA''') is a sub-region of the parahippocampal cortex that lies medially in the inferior temporo-occipital cortex. PPA plays an important role in the encoding and recognition of environmental scenes (rather than faces). fMRI studies indicate that this region of the brain becomes highly active when human subjects view topographical scene stimuli such as images of landscapes, cityscapes, or rooms (i.e. images of "places"). Furthermore, according to work by Pierre Mégevand et al. in 2014, stimulation of the region via intracranial electrodes yields intense topographical visual hallucinations of places and situations.<ref>{{cite journal | vauthors = Mégevand P, Groppe DM, Goldfinger MS ''et al'' | year = 2014 | title = Seeing Scenes: Topographic Visual Hallucinations Evoked by Direct Electrical Stimulation of the Parahippocampal Place Area | journal = Journal of Neuroscience | volume = 34 | issue = 16| pages = 5399–5405 | doi = 10.1523/jneurosci.5202-13.2014 | pmid = 24741031 | pmc = 6608225 }}</ref> The region was first described by Russell Epstein and Nancy Kanwisher in 1998 at MIT,<ref name="urlA cortical representation of the local visual environment : Abstract : Nature">{{cite journal |title=A cortical representation of the local visual environment| volume=392 |issue=6676 |doi=10.1038/33402 |pmid=9560155|journal=Nature |pages=598–601 |year=1998 |vauthors=Epstein R|bibcode=1998Natur.392..598E| s2cid=920141 }}</ref> see also other similar reports by Geoffrey Aguirre<ref name="urlThe Parahippocampus Subserves Topographical Learning in Man -- Aguirre et al. 6 (6): 823 -- Cerebral Cortex">{{cite journal |title=The Parahippocampus Subserves Topographical Learning in Man |author= Aguirre|display-authors=etal|volume=6 |issue=6|pages=823–9 |journal= Cerebral Cortex|doi=10.1093/cercor/6.6.823|pmid=8922339 |year=1996 |doi-access=free}}</ref><ref name="urlNeuron - An Area within Human Ventral Cortex Sensitive to “Building” Stimuli">{{cite web|url=http://www.neuron.org/content/article/abstract?uid=PIIS0896627300805462|archive-url=https://archive.today/20130113021511/http://www.neuron.org/content/article/abstract?uid=PIIS0896627300805462|url-status=dead|archive-date=2013-01-13|title=Neuron - An Area within Human Ventral Cortex Sensitive to "Building" Stimuli|access-date=2009-11-03}}</ref> and Alumit Ishai.<ref name="urlDistributed representation of objects in the human ventral visual pathway — PNAS">{{cite journal |title=Distributed representation of objects in the human ventral visual pathway — PNAS |doi=10.1073/pnas.96.16.9379 |pmid=10430951 |volume=96 |issue=16 |year=1999 |journal=Proceedings of the National Academy of Sciences |pages=9379–9384 |vauthors=Ishai A|pmc=17791 |bibcode=1999PNAS...96.9379I |doi-access=free }}</ref>

Damage to the PPA (for example, due to stroke) often leads to a syndrome in which patients cannot visually recognize scenes even though they can recognize the individual objects in the scenes (such as people, furniture, etc.). The PPA is often considered the complement of the fusiform face area (FFA), a nearby cortical region that responds strongly whenever faces are viewed, and that is believed to be important for face recognition.

===Social context=== Additional research has suggested that the right parahippocampal gyrus in particular has functions beyond the contextualizing of visual background. Tests by a California-based group led by Katherine P. Rankin indicate that the lobe may play a crucial role in identifying social context as well, including paralinguistic elements of verbal communication.<ref name="urlKatherine P. Rankin, a Neuropsychologist, Studies Sarcasm - NYTimes.com">{{cite news |url=https://www.nytimes.com/2008/06/03/health/research/03sarc.html?em&ex=1212724800&en=51b0f096761db2f9&ei=5087%0A+ |title=Katherine P. Rankin, a Neuropsychologist, Studies Sarcasm - NYTimes.com |work= The New York Times|access-date=2009-11-03 | first=Dan | last=Hurley | date=2008-06-03}}</ref> For example, Rankin's research suggests that the right parahippocampal gyrus enables people to detect sarcasm.

==Additional images== <gallery> File:Parahippocampal gyrus animation.gif|Animation. Parahippocampal gyrus shown red. File:Gray727 parahippocampal gyrus.png|Medial surface of left cerebral hemisphere. Parahippocampal gyrus shown in orange. File:Human brain inferior-medial view description.JPG|Human brain inferior-medial view. Parahippocampal gyrus labelled as #5 File:Gehirn Frontalschnitt hippocampus.png|Coronal section. Parahippocampal gyrus labelled at bottom center. File:Hippocampus (brain).jpg|Coronal section of hippocampus. Parahippocampal gyrus labelled at bottom. File:Gehirn, basal - beschriftet lat.svg|Basal view of a human brain. File:Parahippocampal gyrus.jpg|Basal view of a human brain. Parahippocampal gyrus shown in yellow. File:Slide4MIR.JPG|Close up of parahippocampal gyrus. Parahippocampal - DK ATLAS.png|Parahippocampal gyrus, shown in right cerebral hemisphere. File:Parahippocampal gyrus coronal sections.gif|Parahippocampal gyrus highlighted in green on coronal T1 MRI images File:Parahippocampal gyrus sagittal sections.gif|Parahippocampal gyrus highlighted in green on sagittal T1 MRI images File:Parahippocampal gyrus transversal sections.gif|Parahippocampal gyrus highlighted in green on transversal T1 MRI images </gallery>

==References== {{Reflist|2}}

==External links== {{Commons category|Parahippocampal gyrus}} * {{BrainInfo|hier|146}} * https://web.archive.org/web/20090505072544/http://www2.umdnj.edu/~neuro/studyaid/Practical2000/Q35.htm * [http://www.temporal-lobe.com Temporal-lobe.com An interactive diagram of the rat parahippocampal-hippocampal region]

Category:Hippocampus (brain) Category:Gyri