Retrosplenial area: characteristics and functions

This part of the cingulum of the brain is involved in several higher mental functions.

The retrosplenial area is a brain area linked to episodic and contextual memory, navigation or imagination of future events and scenes. Its importance lies in being a necessary part of a set of regions involved in the management of brain activity when the mind and the organism are at rest.

In this article we explain what the retrosplenial area is, where it is located, what are its functions and what are its functions.where it is located, what are the main functions it carries out and what type of disorders can originate if a damage occurs in this region of the brain.

Retrosplenial area: definition and neuroanatomical localization

The retrosplenial area or retrosplenial cortex (RSC) is a brain region located in the inferior part of the cingulate gyrus, extending around the splenium of the corpus callosum, a structure connecting the two cerebral hemispheres.extending around the splenium of the corpus callosum, a structure connecting 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 with the posterior cingulate cortex (PCC) and has strong connections with the pregenual and subgenual anterior cingulate cortex. The PCC and the PCR 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 associated pathologies in these brain areas would be implicated in many amnestic syndromes.

Other notable connections have also been described between the SRA and different areas of the prefrontal cortex (namely Brodmann's areas 46, 9, 10 and 11), which provide an indirect route for the hippocampus to connect with the dorsolateral prefrontal cortex, and vice versa.

Functions

Studies have determined that the retrosplenial area plays a significant role in spatial and spatial memory. a significant role in spatial and episodic (or contextual) memory, navigation, imagining future events, and scene processing.. This brain region is also involved in processes involving the recognition of permanent and non-moving environmental landmarks, as well as in spatial judgments.

Below we will look in more detail at some of the main tasks in which the retrosplenial area is involved:

Navigation, spatial and contextual memory.

Studies conducted with functional MRI have found that activity in the retrosplenial area is modulated by a wide variety of processes, ranging from basic speech production and comprehension to motivation and pain. However, However, its involvement in navigation and spatial memory tasks seems to be very clearand 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 versus remote experiences, although it seems to be activated when we recall 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 is involved in spatial navigation tasks. These include passive viewing of navigational images, mental navigation, and interactive navigation in virtual reality environments..

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

In relation to virtual environments, a study using a virtual reality simulation of central London showed 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. Thus, it appears that the activity of this brain region would vary depending on specific circumstances and priorities.

Finally, with regard to the relationship of the retrosplenial area and scene processing, it has been suggested that this region may process scene-relevant relations, such as those arising fromsuch as that arising from objects and their context. In several 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 such 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 hippocampal damage not only cannot remember past experiences, but also have difficulty imagining fictional and future experiences; and second, the discovery that remembering past experiences activates many brain regions that are also activated when imagining plausible personal future and fictional experiences.

Another meta-analysis including several studies on this question 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 and the imagination of future events places this brain region in a crucial position for understanding these cognitive processes. A recent functional MRI study examined brain activation during the retrieval of autobiographical events, movie episodes, and actual news clippings, as well as imagined events of all three types. The results concluded that there was greater activation upon retrieval of real events.

Related disorders

Lesions in the retrosplenial area may produce an amnestic 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 lesion). The extent of retrograde amnesia varies from less than 1 year to 10 years.

In turn, damage in the right portion of the retrosplenial area can generate a selective deficit in spatial orientation and an amnesia of topographical features: the subject can recognize buildings and landscapes.The subject can recognize familiar buildings and landscapes, but loses the positional relationship between two known sites. This occurs because it is possible that this area plays an important role in the encoding 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 unable to comprehend directional information from cues from particular landmarks.

Damage to the retrosplenial area can also compromise learning in new environments. Subjects with hippocampal damage also show difficulty navigating in familiar and novel environments, but unlike those with lesions in the retrosplenial area, they are generally able to orient themselves in such environments and retain their sense of direction.

Bibliographic references:

• Clark, D. L., Boutros, N. N., & Méndez, 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.