The parahippocampal gyrus (or hippocampal gyrus') is a

grey matter Grey matter, or gray matter in American English, is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil ( dendrites and unmyelinated axons), glial cells ( astrocytes and oligodendrocytes), synapses, ...

cortical region, a

gyrus In neuroanatomy, a gyrus (: gyri) is a ridge on the cerebral cortex. It is generally surrounded by one or more sulci (depressions or furrows; : sulcus). Gyri and sulci create the folded appearance of the brain in humans and other mammals. ...

of the

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

that surrounds the

hippocampus The hippocampus (: hippocampi; via Latin from Ancient Greek, Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the ...

and is part of the

limbic system The limbic system, also known as the paleomammalian cortex, is a set of brain structures located on both sides of the thalamus, immediately beneath the medial temporal lobe of the cerebrum primarily in the forebrain.Schacter, Daniel L. 2012. ''P ...

. The region plays an important role in

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembe ...

encoding In communications and Data processing, information processing, code is a system of rules to convert information—such as a letter (alphabet), letter, word, sound, image, or gesture—into another form, sometimes data compression, shortened or ...

and retrieval. It has been involved in some cases of

hippocampal sclerosis Hippocampal sclerosis (HS) or mesial temporal sclerosis (MTS) is a neuropathological condition with severe neuronal cell loss and gliosis in the hippocampus. Neuroimaging tests such as magnetic resonance imaging (MRI) and positron emission tomogr ...

. Asymmetry has been observed in

schizophrenia Schizophrenia () is a mental disorder characterized variously by hallucinations (typically, Auditory hallucination#Schizophrenia, hearing voices), delusions, thought disorder, disorganized thinking and behavior, and Reduced affect display, f ...

Structure

The anterior part of the gyrus includes the perirhinal and

entorhinal The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.Integrating time from experience in th ...

cortices. The term parahippocampal cortex is used to refer to an area that encompasses both the

posterior parahippocampal gyrus The posterior parahippocampal gyrus is a portion of the parahippocampal gyrus. It can show deterioration in Alzheimer's disease Alzheimer's disease (AD) is a neurodegenerative disease and the cause of 60–70% of cases of dementia. The ...

and the medial portion of the

fusiform gyrus The fusiform gyrus, also known as the ''lateral occipitotemporal gyrus'','' ''is part of the temporal lobe and occipital lobe in Brodmann area 37. The fusiform gyrus is located between the lingual gyrus and parahippocampal gyrus above, and ...

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 Recognition may refer to: Machine learning *Pattern recognition, a branch of machine learning which encompasses the meanings below Biometric * Recognition of human individuals, or biometrics, used as a form of identification and access control ...

of environmental scenes (rather than faces).

fMRI Functional magnetic resonance imaging or functional MRI (fMRI) measures brain activity by detecting changes associated with blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area o ...

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 Pierre is a masculine given name. It is a French form of the name Peter. Pierre originally meant "rock" or "stone" in French (derived from the Greek word πέτρος (''petros'') meaning "stone, rock", via Latin "petra"). It is a translation ...

et al. in 2014, stimulation of the region via intracranial electrodes yields intense topographical visual hallucinations of places and situations. The region was first described by

Russell Epstein Russell Epstein is a professor of psychology at the University of Pennsylvania, who studies neural mechanisms underlying visual scene perception, event perception, object recognition, and spatial navigation in humans. His lab studies the role of th ...

and

Nancy Kanwisher Nancy Gail Kanwisher FBA (born 1958) is the Walter A Rosenblith Professor of Cognitive Neuroscience in the Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology and a researcher at the McGovern Institute for B ...

in 1998 at MIT, see also other similar reports by

Geoffrey Aguirre Geoffrey, Geoffroy, Geoff, etc., may refer to: People * Geoffrey (given name), including a list of people with the name Geoffrey or Geoffroy * Geoffroy (surname), including a list of people with the name * Geoffroy (musician) (born 1987), Canadia ...

and Alumit Ishai. 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 The fusiform face area (FFA, meaning spindle-shaped face area) is a part of the human visual system (while also activated in people blind from birth) that is specialized for facial recognition. It is located in the inferior temporal cortex (I ...

(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. For example, Rankin's research suggests that the right parahippocampal gyrus enables people to detect sarcasm.

Additional images

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

. 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

References

External links

* * https://web.archive.org/web/20090505072544/http://www2.umdnj.edu/~neuro/studyaid/Practical2000/Q35.htm
Temporal-lobe.com An interactive diagram of the rat parahippocampal-hippocampal region
{{Authority control Hippocampus (brain) Gyri