Perirhinal cortex
Encyclopedia
Perirhinal cortex is a cortical region in the medial temporal lobe that is made up of Brodmann area
s 35
and 36
. In rats, it is located along and dorsal
to the rhinal sulcus. It receives highly-processed sensory information from all sensory regions, and is generally accepted to be an important region for memory
. It is bordered caudally by postrhinal cortex
or parahippocampal cortex
(homologous regions in rodents and primates, respectively) and ventrally and medially by entorhinal cortex
.
Area 36 is six-layered, dysgranular cortex, meaning that its layer IV is relatively sparse. Area 35 is agranular (lacking any cells in layer IV).
areas, whereas, in the rat, its inputs are primarily olfactory and, to a lesser extent, auditory
. Outputs to orbitofrontal cortex
and medial prefrontal cortex
regions (such as prelimbic and infralimbic
) have been described. Perirhinal cortex also sends output to a number of subcortical structures, including the basal ganglia
, the thalamus
, the basal forebrain
, and the amygdala
.
It also has direct connections with hippocampus
region CA1 and the subiculum
. Perirhinal cortex projects to distal CA1 pyramidal cells, overlapping the projections from entorhinal cortex
. The same CA1 cells send return projections back to perirhinal cortex. Inputs from subiculum terminate in both superficial and deep layers.
regions and from the superior temporal sulcus
. Other inputs include anterior cingulate and insular regions
, in addition to prefrontal
projections.
inputs from piriform and insular cortices, in addition to inputs from entorhinal cortex and frontal regions.
Brodmann area
A Brodmann area is a region of the cerebral cortex defined based on its cytoarchitectonics, or structure and organization of cells.-History:...
s 35
Brodmann area 35
Brodmann area 35, together with Brodmann area 36, is most frequently referred to as perirhinal cortex.-Human:This area is known as perirhinal area 35. It is a subdivision of the cytoarchitecturally defined hippocampal region of the cerebral cortex. In the human it is located along the rhinal sulcus...
and 36
Brodmann area 36
Ectorhinal area 36 is a subdivision of the cytoarchitecturally defined temporal region of cerebral cortex. With its medial boundary corresponding approximately to the rhinal sulcus it is located primarily in the fusiform gyrus...
. In rats, it is located along and dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
to the rhinal sulcus. It receives highly-processed sensory information from all sensory regions, and is generally accepted to be an important region for memory
Memory
In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....
. It is bordered caudally by postrhinal cortex
Postrhinal cortex
The Postrhinal cortex is an area of the brain which borders above the entorhinal cortex. It is the cortical region dorsally adjacent and caudal to the posterior rhinal sulcus.It is implicated in the role of memory and spatial navigation....
or parahippocampal cortex
Parahippocampal gyrus
The parahippocampal gyrus is a grey matter cortical region of the brain that surrounds the hippocampus. This region plays an important role in memory encoding and retrieval....
(homologous regions in rodents and primates, respectively) and ventrally and medially by entorhinal cortex
Entorhinal cortex
The entorhinal cortex is located in the medial temporal lobe and functions as a hub in a widespread network for memory and navigation. The EC is the main interface between the hippocampus and neocortex...
.
Structure
The perirhinal cortex is composed of two regions: areas 36 and 35. Area 36 is sometimes divided into three subdivisions: 36d is the most rostral and dorsal, 36r ventral and caudal, and 36c the most caudal. Area 35 can be divided in the same manner, into 35d and 35v (for dorsal and ventral, respectively).Area 36 is six-layered, dysgranular cortex, meaning that its layer IV is relatively sparse. Area 35 is agranular (lacking any cells in layer IV).
Connectivity
The monkey perirhinal cortex receives a majority of its input from high-level visualVisual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....
areas, whereas, in the rat, its inputs are primarily olfactory and, to a lesser extent, auditory
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
. Outputs to orbitofrontal cortex
Orbitofrontal cortex
The orbitofrontal cortex is a prefrontal cortex region in the frontal lobes in the brain which is involved in the cognitive processing of decision-making...
and medial prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
regions (such as prelimbic and infralimbic
Infralimbic cortex
Infralimbic cortex is a cortical region in the ventromedial prefrontal cortex which is important in tonic inhibition of subcortical structures and emotional responses, such as fear.-Primates:...
) have been described. Perirhinal cortex also sends output to a number of subcortical structures, including the basal ganglia
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
, the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
, the basal forebrain
Basal forebrain
The basal forebrain is a collection of structures located ventrally to the striatum. It is considered to be the major cholinergic output of the central nervous system . It includes a group of structures that lie near the bottom of the front of the brain, including the nucleus basalis, diagonal band...
, and the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
.
It also has direct connections with hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
region CA1 and the subiculum
Subiculum
The subiculum is the most inferior component of the hippocampal formation. It lies between the entorhinal cortex and the CA1 subfield of the hippocampus proper.-Paths:...
. Perirhinal cortex projects to distal CA1 pyramidal cells, overlapping the projections from entorhinal cortex
Entorhinal cortex
The entorhinal cortex is located in the medial temporal lobe and functions as a hub in a widespread network for memory and navigation. The EC is the main interface between the hippocampus and neocortex...
. The same CA1 cells send return projections back to perirhinal cortex. Inputs from subiculum terminate in both superficial and deep layers.
Primates
Visual areas TE and TEO send and receive a significant reciprocal connection with perirhinal cortex. Weaker, but still significant, projections come from other parahippocampalParahippocampal gyrus
The parahippocampal gyrus is a grey matter cortical region of the brain that surrounds the hippocampus. This region plays an important role in memory encoding and retrieval....
regions and from the superior temporal sulcus
Superior temporal sulcus
The superior temporal sulcus is the sulcus separating the superior temporal gyrus from the middle temporal gyrus in the temporal lobe of the brain. The superior temporal sulcus is the first sulcus inferior to the lateral fissure....
. Other inputs include anterior cingulate and insular regions
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
, in addition to prefrontal
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
projections.
Rodents
Auditory inputs from temporal cortical regions are the primary inputs to rat 36d, with visual inputs becoming more prominent closer to the postrhinal cortical border. Area 36d projects to 36v and then to 35, which forms the primary output region of perirhinal cortex. Inputs to area 35 more strongly reflect olfactory and gustatoryTaste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....
inputs from piriform and insular cortices, in addition to inputs from entorhinal cortex and frontal regions.