The retrosplenial cortex (RSC) is a

cortical area The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...

in the brain comprising Brodmann areas 29 and 30. It is secondary association cortex, making connections with numerous other brain regions. The region's name refers to its anatomical location immediately behind the

splenium The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental m ...

of the

corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mam ...

in primates, although in rodents it is located more towards the brain surface and is relatively larger. Its function is currently not well understood, but its location close to visual areas and also to the hippocampal spatial/memory system suggest it may have a role in mediating between perceptual and memory functions, particularly in the spatial domain. However, its exact contribution to either space or memory processing has been hard to pin down.

Anatomy

There is large variation in the region's size across different species. In humans it comprises roughly 0.3% of the entire cortical surface whereas in rabbits it is at least 10% and in rats it extends for more than half the cerebrum dorso-ventrally, making it one of the largest cortical regions. On the basis of its microscopic cellular structure it is divided into dysgranular (area 30) and granular (area 29) regions. It has dense reciprocal projections with the visual cortex, postsubiculum (also known as dorsal

presubiculum Area 27 of Brodmann-1909 is a cytoarchitecturally defined cortical area that is a rostral part of the parahippocampal gyrus. It is commonly regarded as a synonym of presubiculum. The dorsal part of the presubiculum is more commonly known as the ...

) and with

anterior thalamic nuclei The anterior nuclei of thalamus (or anterior nuclear group) are a collection of nuclei at the rostral end of the dorsal thalamus. They comprise the anteromedial, anterodorsal, and anteroventral nuclei. Inputs and outputs The anterior nuclei rece ...

and 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 system, a ...

Neurophysiology

Neurophysiological studies of retrosplenial cortex have mainly been done in rats. Early work showed that around 8.5% of neurons in the retrosplenial cortex are

head direction cells Head direction (HD) cells are neurons found in a number of brain regions that increase their firing rates above baseline levels only when the animal's head points in a specific direction. They have been reported in rats, monkeys, mice, chinchillas ...

while other neurons have correlated with movement parameters such as spatial location and running speed. Recent studies have shown that retrosplenial neuronal activity reflects multiple parameters simultaneously including which environment the animal is currently in, its spatial position in the environment, its current head direction and running speed, as well as whether the animal is turning or plans to turn in the future. Many of these features of retrosplenial neurophysiology develop slowly as the animal learns to navigate within an environment, consistent with the idea that the retrosplenial cortex participates in the long-term storage of spatial memory.

Function

In humans,

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 implicate the retrosplenial cortex in a wide range of cognitive functions including

episodic memory Episodic memory is the memory of everyday events (such as times, location geography, associated emotions, and other contextual information) that can be explicitly stated or conjured. It is the collection of past personal experiences that occurred ...

, navigation, imagining future events and processing scenes more generally. Rodent studies suggest the region is important for using surrounding visual cues to carry out these tasks. Retrosplenial cortex is particularly responsive to permanent, non-moving environmental landmarks and is also implicated in using them to make spatial judgements. It has also been suggested that retrosplenial cortex may translate between egocentric (self-centred) and allocentric (world-centred) spatial information, based upon its anatomical location between the

(where there are allocentric

place cell A place cell is a kind of pyramidal neuron in the hippocampus that becomes active when an animal enters a particular place in its environment, which is known as the place field. Place cells are thought to act collectively as a cognitive repres ...

representations) and the

parietal lobe The parietal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The parietal lobe is positioned above the temporal lobe and behind the frontal lobe and central sulcus. The parietal lobe integrates sensory informa ...

(which integrates egocentric sensory information). Competitors in the

World Memory Championships The World Memory Championships is an organized competition of memory sports in which competitors memorize as much information as possible within a given period of time. The championship has taken place annually since 1991, with the exception of ...

are able to perform outstanding feats of memory and show increased

activation in their retrosplenial cortex than normal controls when doing so. This is thought to be due to their use of a spatial learning strategy or

mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and imag ...

device known as the

method of loci The method of loci is a strategy for memory enhancement, which uses visualizations of familiar spatial environments in order to enhance the recall of information. The method of loci is also known as the memory journey, memory palace, journey m ...

. The region also displays slow-wave

theta rhythm Theta waves generate the theta rhythm, a neural oscillation in the brain that underlies various aspects of cognition and behavior, including learning, memory, and spatial navigation in many animals. It can be recorded using various electrophysi ...

icity and when people retrieve autobiographical memories, there is theta band interaction between the retrosplenial cortex and the medial

temporal lobe The temporal lobe is one of the four Lobes of the brain, major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe ...

Pathology

The retrosplenial cortex is one of several brain areas that produces both an anterograde and retrograde amnesia when damaged. People with lesions involving the retrosplenial cortex also display a form of

topographical disorientation Topographical disorientation is the inability to orient oneself in one's surroundings, sometimes as a result of focal brain damage. This disability may result from the inability to make use of selective spatial information (e.g., environmental l ...

whereby they can recognise and identify environmental landmarks, but are unable to use them to orientate themselves. The retrosplenial cortex is one of the first regions to undergo pathological changes in

Alzheimer's disease Alzheimer's disease (AD) is a neurodegeneration, neurodegenerative disease that usually starts slowly and progressively worsens. It is the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in short-term me ...

and its

prodromal In medicine, a prodrome is an early sign or symptom (or set of signs and symptoms) that often indicates the onset of a disease before more diagnostically specific signs and symptoms develop. It is derived from the Greek word ''prodromos'', meaning ...

phase of

mild cognitive impairment Mild cognitive impairment (MCI) is a neurocognitive disorder which involves cognitive impairments beyond those expected based on an individual's age and education but which are not significant enough to interfere with instrumental activities o ...

. There are also experimental findings showing that layer 5 of the retrosplenial cortex is likely responsible for dissociative states of consciousness in mammals.

Gallery

File:Brodmann Cytoarchitectonics 29.png,

Brodmann area 29 Brodmann area 29, also known as granular retrolimbic area 29 or granular retrosplenial cortex, is a cytoarchitecturally defined portion of the retrosplenial region of the cerebral cortex. In the human it is a narrow band located in the isthmus ...

File:Brodmann Cytoarchitectonics 30.png,

Brodmann area 30 Brodmann area 30, also known as agranular retrolimbic area 30, is a subdivision of the cytoarchitecturally defined retrosplenial region of the cerebral cortex. In the human it is located in the isthmus of cingulate gyrus. Cytoarchitecturally it ...

References

{{Telencephalon Cerebral cortex Medial surface of cerebral hemisphere