The retrosplenial area is an area of the brain linked to episodic and contextual memory, navigation or imagining future events and scenes. Its importance lies in being a necessary part of a set of regions that participate in the management of brain activity when the mind and body are at rest.
In this article we explain what the retrosplenial area consists of where it is located, what are the main functions it carries out and what type of disorders can arise if damage occurs in this region of the brain.
Retrosplenial area: definition and neuroanatomical location
The retrosplenial area or cortex (REC) is a region of the brain located in the lower part of the cingulate gyrus, extending around the splenium of the corpus callosum, a structure that connects the two cerebral hemispheres. It comprises Brodmann’s areas 29 and 30 and together with the precuneus and posterior cingulate form a posterior nucleus that is sometimes called the “posteromedial cortex.”
This brain region is reciprocally connected with the posterior cingulate cortex (PCC) and has strong connections with the pregenual and subgenual anterior cingulate cortex. The CCP and CRE are part of the default brain network, a set of brain areas that are activated (up to 20% above other regions) when the mind wanders and is at rest.
Animal studies have revealed that the retrosplenial area would have reciprocal connections with these three regions: the hippocampus, the parahippocampal gyrus and certain nuclei of the thalamus Traumatic damage and pathologies associated with these areas of the brain would be involved in many amnestic syndromes.
Likewise, other notable connections have been described between the CRE and different areas of the prefrontal cortex (specifically Brodmann areas 46, 9, 10 and 11), which provide an indirect route for the hippocampus to connect with the dorsolateral prefrontal cortex, and vice versa.
The studies carried out have determined that the retrosplenial area has a significant role in spatial and episodic (or contextual) memory, navigation, imagining future events, and scene processing This brain region would also be involved in processes that involve recognizing permanent and non-mobile environmental reference points, as well as in spatial judgments.
Below we will see in more detail some of the main tasks in which the retrosplenial area is involved:
Navigation, spatial and contextual memory
Studies carried out with functional magnetic resonance imaging have proven that activity in the retrosplenial area is modulated by a wide variety of processes, ranging from the production and basic understanding of speech, to motivation and pain. However, their participation in navigation and spatial memory tasks seems to be very clear and most brain imaging studies confirm it.
In a recent meta-analysis, the retrosplenial area showed significant activation during the retrieval of autobiographical information, and more specifically in recent experiences versus remote experiences, although it seems to be activated when we remember any type of experience in which we are protagonists, regardless that the tone is more neutral or emotional.
On the other hand, it has also been observed that the retrosplenial area participates in spatial navigation tasks. These include passive navigation image display, mental navigation and interactive navigation in virtual reality environments
Furthermore, activity has also been seen during learning in new and newly learned environments, as well as in very familiar environments. In fact, it seems difficult to find any navigation or topographic memory task in which this region is not activated.
In relation to virtual environments, a study using a virtual reality simulation of central London found that activity in the retrosplenial area increased when topographic representations had to be updated, integrated or manipulated for route planning. or when new topographic information had to be acquired. Therefore, it seems that the activity of this brain region would vary depending on specific circumstances and priorities.
Finally, with respect to the relationship of the retrosplenial area and scene processing, it has been suggested that this region could process relationships relevant to the scene, such as that which arises from objects and their context. In various studies it has been determined that this area is activated when seeing objects strongly associated with a specific context, and not the other way around (when said association is weak).
Imagination of future events
In recent years, new research has emerged in the field of memory based on the following premises: first, the fact that patients with bilateral damage to the hippocampus not only cannot remember past experiences, but also have difficulties imagining fictitious experiences. and future and second, the discovery that remembering past experiences activates many brain regions that are also activated when imagining a plausible personal future and fictional experiences.
In another meta-analysis that included several studies on this issue, it was confirmed that the retrosplenial area is part of a common “core network” that maintains a variety of cognitive functions. This network would support the construction of “scenes” (the process of mentally generating and maintaining a complex and coherent image or event), hence it is essential in autobiographical memory, navigation or thinking about the future
The link between memory and navigation with the imagination of future events places this brain region in a crucial position to understand these cognitive processes. A recent fMRI study examined brain activation during retrieval of autobiographical events, movie episodes, and real news clippings, as well as imagined events of all three types. The results concluded that there was greater activation when recovering real events.
Lesions in the retrosplenial area can produce an amnestic syndrome characterized by anterograde loss (inability to store new events) of verbal and non-verbal memories, accompanied by mild retrograde amnesia (inability to remember events that occurred before the injury). The extent of retrograde amnesia varies from less than 1 year to 10 years.
In turn, damage to the right portion of the retrosplenial area can generate a selective deficit in spatial orientation and an amnesia of topographic features: The subject can recognize familiar buildings and landscapes, but loses the positional relationship between two known places. This occurs because this area is likely to play an important role in the coding of novel sites and their relationships.
In most cases patients can recognize landmarks in their neighborhood, for example; but they cannot navigate effectively in familiar environments, indicating that they are not able to understand directional information from cues at certain landmarks.
Damage to the retrosplenial area can also compromise learning in new environments Subjects with damaged hippocampus also show difficulties navigating in familiar and novel environments, but unlike what happens with people who have lesions in the retrosplenial area, they are generally able to orient themselves in these environments and retain their sense of meaning. the orientation.
