Retrosplenial area: characteristics and functions

The retrosplenial area is an area of ​​the brain linked to episodic and contextual memory, navigation, or imagining of 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 kind of disorders can be caused if damage occurs in this region of the brain.

• Related article: "Cingulate gyrus (brain): anatomy and functions"

Retrosplenial area: definition and neuroanatomical location

The retrosplenial area or cortex (CRE) is a region of the brain located at the bottom 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 sometimes referred to as the “posteromedial cortex”.

This brain region is reciprocally connected to the posterior cingulate cortex (PCC) and has strong connections to the pregenual and subgenual anterior cingulate cortex. The CCP and the 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: hippocampus, parahippocampal gyrus, and certain nuclei of the thalamus. Traumatic damage and pathologies associated with these areas of the brain would be implicated in many amnestic syndromes.

Likewise, other notable connections have been described between the CRE and different areas of the prefrontal cortex (specifically areas 46, 9, Brodmann 10 and 11), which provide an indirect route for the hippocampus to connect to the dorsolateral prefrontal cortex, and vice versa.

functions

Studies have determined that the retrosplenial area has a significant role in spatial and episodic (or contextual) memory, navigation, imagination of future events, and scene processing. This brain region would also be involved in the processes that involve recognizing permanent and non-mobile environmental reference points, as well as in judgments of a spatial nature.

Next 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 have verified that the activity in the retrosplenial area is modulated by a wide variety of processes, ranging from the production and basic comprehension of speech, to motivation and pain. However, its participation in navigation tasks and spatial memory seems to be very clear, and most brain imaging studies confirm this.

In a recent meta-analysis, the retrosplenial area showed significant activation during the retrieval of autobiographical information, and more specifically in recent experiences versus to remote experiences, although it seems to be activated when we remember any type of experience in which we are protagonists, regardless of whether 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 the passive display of navigation images, mental navigation and interactive navigation in virtual reality environments.

In addition, activity has also been seen during learning of new environments and those recently learned, as well as in very familiar environments. In fact, it seems difficult to find any topographic memory or navigation task in which this region is not activated.

In relation to virtual environments, in a study that used a virtual reality simulation of central London, it was found that activity in the area retrosplenial increased when topographical representations needed to be updated, integrated, or manipulated for route planning or when new data had to be acquired. topographic information. Therefore, it seems that the activity of this brain region would vary depending on the specific circumstances and priorities.

Finally, regarding 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 possible to determine 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).

The imagination of future events

In recent years, new research in the field of memory has emerged based on the following premises: first, the fact that patients with bilateral hippocampal damage not only cannot recall past experiences, but also have difficulty imagining fictional experiences and future; and second, the discovery that remembering past experiences activates many brain regions that are also activated when imagining plausible personal futures and fictional experiences.

In another meta-analysis that included several studies on this question, 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 imaginative navigation of future events places this brain region in a crucial position for understanding these cognitive processes. A recent fMRI study examined brain activation during recovery from autobiographical events, episodes from a film, and actual news clippings, as well as imagined events from all three guys. The results concluded that there was greater activation before the recovery of real events.

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Related disorders

Lesions in the retrosplenial area can produce an amnesic syndrome characterized by anterograde loss (inability to store new events) of verbal and nonverbal memories, accompanied by mild retrograde amnesia (inability to recall 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: Subject can recognize familiar buildings and landscapes, but loses positional relationship between two familiar locations. This occurs because it is possible that this area plays 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 capable of understanding directional information from the signs of 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 occurs with People with lesions in the retrosplenial area are generally able to orient themselves in such environments and retain their sense of direction. orientation.

Bibliographic references:

• Clark, D. L., Boutros, N. N., & Mendez, M. F. (2012). The brain and behavior: neuroanatomy for psychologists. Modern Handbook.
• Maddock, R. J. (1999). The retrosplenial cortex and emotion: new insights from functional neuroimaging of the human brain. Trends in neurosciences, 22(7), 310-316.
• Zola-Morgan, S., & Squire, L. R. (1993). Neuroanatomy of memory. Annual review of neuroscience, 16(1), 547-563.