Retrosplenial cortex

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. It has dense reciprocal projections with the visual cortex, postsubiculum (also known as dorsal presubiculum) and with anterior thalamic nuclei and the hippocampus. ==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 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 current head direction and running speed, 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, ==Function==

In humans, fMRI studies implicate the retrosplenial cortex in a wide range of cognitive functions including episodic memory, 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. A review in 2023 suggested its function was "spatial navigation and localization of personally relevant objects". Competitors in the World Memory Championships are able to perform outstanding feats of memory and show increased fMRI 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 device known as the method of loci. The region also displays slow-wave theta rhythmicity and when people retrieve autobiographical memories, there is theta band interaction between the retrosplenial cortex and the medial 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 whereby they can recognise and identify environmental landmarks, but are unable to use them to orientate themselves. 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 File:Brodmann Cytoarchitectonics 30.png|Brodmann area 30 ==References==