Gut microbiota influences cognitive health

A study led from the Higher Council for Scientific Research (CSIC)carried out on 54 healthy people over 55 yearshighlights how different profiles of microbiota are associated with variations in areas of the cerebral cortex related to cognitive functions such as memory, language and emotional processing.

The results suggest that the composition of the microbiota could influence cognitive aging through the gut-brain axis. This finding, published in the journal ‘Scientific Reports‘ opens the door to future research on nutritional interventions to prevent or mitigate age-related cognitive decline.

This work carried out by Computational Modeling of Intelligence Group, of the Center for Automation and Robotics (CSIC-UPM), in collaboration with the group IMDEA-Foodis the first to assess the relationship between the intestinal microbiota and spontaneous brain activity using electroencephalography at rest in healthy people.

Thus, two fundamental findings have been reached according to the brain areas in which differences have been discovered. On the one hand, that the composition of The intestinal microbiota in healthy subjects could influence brain activity. And that, in turn, Brain activity could influence key functions such as memory, language and social cognition during aging (emotion recognition, empathy, social norms and moral reasoning). In conclusion, not all intestinal microbiota are the same, which affects brain activity even in the absence of disease.

Gut-brain axis

The intestinal microbiota is the main regulator of the gut-brain axis, but until now its role was unknown. influence on brain activity. In this work, whose first author is José Ignacio Serrano, and led by María Dolores del Castillo Sobrino, both from CAR-CSIC-UPM, it is suggested that different microbiota profiles in healthy people over 55 years of age are associated with different spontaneous activity in the posterior cortical-medial areas of the brain, involved in functions such as perception, memory and the processing of internal information. This translates into a greater predisposition to certain diseases or health conditions despite having a healthy microbiome.

These brain areas are linked to memory, language and emotional processing, Therefore, it is evident that non-pathological intestinal microbiota profiles are related to brain activity associated with cognitive functions that usually deteriorate with age. In this way, an early modification of the composition of the microbiota, through nutritional changes, could delay or improve the cognitive deterioration related to aging.

Possible key influence of the vagus nerve

The study identifies three groups of healthy subjects (A, B, C) taking into account the analysis of their intestinal microbiota. In two of them (A and B) the predominance of the ‘Bacteroides’ genus of microorganisms is detected and in the third (C) of the ‘Prevotella’ genus, related to the type of diet of the study participants.

The analysis shows different brain activity at rest between the groups in terms of episodic memory (autobiographical memories), language and emotion processing. Significant differences are also observed between the subjects of the three groups, especially between two of them (A, B) and the third (C), in relation to the areas of the precuneus (fundamental for self-awareness, autobiographical memory, visuospatial functions and conscious perception), the posterior cingulate cortex bilaterally (involved in functions such as visuospatial orientation, memory, planning and reflection personal) and the left fusiform gyrus (vital for the recognition of words, objects and faces, as well as for the understanding of language), all in the theta band, waves related to memory and learning processes and emotional processing, among others.

A hypothesis that is being used suggests that each intestinal microbiota profile could modulate the vagus nerve signal differently (one of the main communication routes between the intestine and the brain) and, therefore, produce the specific brain activity found in each group.

Stimulation of the vagus nerve is known to have therapeutic benefits in diseases related to the central nervous system, such as epilepsy and depression. It is also recognized as having an influence on inflammatory processes associated with pathologies such as Parkinson’s disease or autism spectrum disorders. Its modulation, through the stimulation and modification of the signal it transmits, could be the mechanism used by the intestinal microbiota to activate the intestinal vagal afferent fibers, which carry information from the intestine to the brain.