Precuneus: characteristics and functions of this part of the brain.

This part of the cerebral cortex is located in the parietal lobe and has several functions.

The human brain is a complex and fascinating organ. Each cerebral hemisphere is composed of several lobes.

And in the superior parietal lobe, hidden between layers of nerve fibers, we can find the precuneus, a unique region for its characteristics and for the functions that have been attributed to it as the main brain coordination center, as well as for participating in the processes of self-awareness.

In this article we explain what the precuña is, what its structure is and where it is located.What is the prebrain, what is its structure and where is it located, what are its main functions and what role does it play in the development of Alzheimer's disease.

Precuneus: definition, structure and location

The precuina or precuneus is a region located in the superior parietal lobe, hidden in the longitudinal fissure of the brain, between the two hemispheres.between the two hemispheres. It is bordered in front by the marginal branch of the cingulate sulcus, posteriorly by the parietooccipital sulcus, and inferiorly by the subparietal sulcus.

Occasionally, the precuña has also been described as the medial area of the superior parietal cortex. In cytoarchitectonic terms, it corresponds to Brodmann's area 7a subdivision of the parietal region of the cortex.

In addition, it has a complex columnar cortical organization and is one of the brain regions that takes the longest to complete myelination (a process by which axons are coated with myelin to, among other things, improve the speed of nerve impulse transmission). Their morphology shows individual variations, both in shape and longitudinal size.

Likewise, the precuña has numerous neural connectionsAt the cortical level, it connects with sensorimotor areas, with areas linked to executive functions, memory and motor planning, and with the primary visual cortex; and at the subcortical level, it has important connections with the thalamic nuclei and the brainstem.

The precuneus is a structure that has developed more in humans than in animals, since at the evolutionary level there has been a considerable increase in the size (in shape and surface area) of the parietal and frontal lobes of the human cerebral cortex with respect to the rest of the animal kingdom, with all that this implies with respect to the development of higher cognitive functions. It is, therefore, a structure that has aroused a great deal of interest in the neuroscientific communitydespite being anatomically so "elusive" (because of its location).

Functions

The precuneus is one of the main areas of regulation and integration of our brain, and acts as a kind of conductor through which many of the signals necessary for our brain to pass.It acts as a kind of orchestra conductor through which many of the signals necessary for this organ to function as an integrated whole pass.

The following are the different functions attributed to the precuneus:

Autobiographical information (episodic memory).

The precuña works in connection with the left prefrontal cortex, which is involved in processes that have to do with episodic memory and autobiographical memories. In this sense, it is involved in aspects such as attention, episodic memory retrieval, working memory or conscious perception processes.

1. Visuospatial processing

Another of the key functions in which it has been suggested that the precuña is involved is visuospatial processing; this area would be involved in the management of spatial attention, when movements are involved and also when images are generated..

It is also thought to be responsible for motor coordination in divided attention processes, i.e., when attention is required to be shifted to different spatial locations or locations (e.g., when writing a text or drawing a picture). In addition, the precuneus would be activated, together with the premotor cortex, in mental operations that require visuospatial processing.

2. Self-awareness

Several investigations have linked the precuina to processes involving self-awareness; in this sense, this brain region would have a relevant role in the integration of the perception of ourselves, in a network of spatial, temporal and social relationships. The precuña would be in charge of generating this sensation of continuity between brain, body and environment.

In studies with functional images, it has been observed that this brain structure analyzes and interprets the this brain structure analyzes and interprets the "intention" of others with respect to ourselves.that is, it would act as a mechanism for analyzing the judgments of others that require an adequate interpretation in order to act accordingly (e.g., with empathy).

3. Conscious perception

In addition to having a relevant role in processes of self-awareness, it has been suggested that the precuneus may be, together with the posterior cingulate cortex, relevant for conscious processing and perception, relevant for the processing and conscious perception of information..

It has been observed that during wakefulness brain glucose metabolism is significantly increased, contrary to what occurs when under the influence of anesthesia. In addition, during slow wave sleep and rapid eye movement sleep or REM sleep, the precuña would be practically deactivated.

On the other hand, it is believed that the cognitive functions related to this brain region could contribute to the integration of internal information (coming from the brain and our organism) with environmental or external information; thus, the precuña would have an essential role in the processes that generate consciousness and the mind in general.

4. Integrative nucleus

An increasing number of studies support the role of the precuña as an integrating center of neural networks. as an integrating center of neural networks of the brain, due to its high centrality in the cortical network of this organ and its numerous and powerful connections with prefrontal areas in charge of executive functions such as planning, supervision and decision making.

Precognition in Alzheimer's disease

Alzheimer's disease, in its early stage, begins with metabolic problems in the area of the medial parietal lobes.. It appears that it is the enlargement of these brain regions that confers a certain vulnerability to the subsequent neurodegeneration suffered by these patients.

Several studies have suggested that there may be a relationship between precuña and the development of this serious disease. As mentioned above, the precuña has evolved differently in humans than in animals: the main difference with respect to other primates, for example, is that this structure has particularly high metabolic levels.

Apparently, the precuticle has higher levels of metabolic expenditure than would be appropriate for its size, which is also true for its metabolic values.This is also true for its thermal values. The curious thing is that Alzheimer's disease begins with metabolic problems precisely in the deep medial parietal area, where the precuneus is located. And a characteristic of Alzheimer's is the phosphorylation of tau proteins, which occurs in mammals that hibernate in response to temperature changes.

What neuroscientists suggest is that a pathology as frequent and characteristic of humans as Alzheimer's would be associated with areas of the brain that have a specific morphology in humans as well. And what they question is whether the increase in the complexity of these brain areas could also have led to an increase in Biological complexity which, secondarily, could lead to an increase in the metabolic load, oxidative stress and cellular problems that predispose a person to Alzheimer's disease.

Nevertheless, research continues on the possible link between the precuticle and other similar structures with the development of this and other neurodegenerative diseases, with the aim of finding new drugs and therapeutic targets to cure or at least slow down their progression.

Bibliographic references:

• Cavanna, A.E., & Trimble, M.R. (2006). The precuneus: a review of its functional anatomy and behavioural correlates. Brain, 129(3), pp. 564 - 583.
• Miners, J.S., Palmer, J.C., & Love, S. (2016). Pathophysiology of Hypoperfusion of the Precuneus in Early Alzheimer's Disease. Brain Pathology, 26(4), pp. 533 - 541.