The parahippocampal gyrus (or hippocampal gyrus') is a

grey matter Grey matter 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, and capillaries. Grey matter is ...

cortical region of the

brain A brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as Visual perception, vision. I ...

that surrounds the

hippocampus The hippocampus (via Latin from Greek , 'seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic syste ...

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 remember ...

encoding and

retrieval Retrieval could refer to: Computer science * RETRIEVE, Tymshare database that inspired dBASE and others * Data retrieval * Document retrieval * Image retrieval * Information retrieval * Knowledge retrieval * Medical retrieval * Music information ...

. It has been involved in some cases of hippocampal sclerosis. Asymmetry has been observed in

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social w ...

Structure

The anterior part of the gyrus includes the

perirhinal The perirhinal cortex is a cortical region in the medial temporal lobe that is made up of Brodmann areas 35 and 36. It receives highly processed sensory information from all sensory regions, and is generally accepted to be an important region f ...

and entorhinal cortices. 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 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 the inf ...

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: *Award, something given in recognition of an achievement Machine learning *Pattern recognition, a branch of machine learning which encompasses the meanings below Biometric * Recognition of human individuals, or biomet ...

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 ...

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. The region was first described by Russell Epstein and Nancy Kanwisher in 1998 at MIT, see also other similar reports by Geoffrey Aguirre 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 ( ...

(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