Is Modern Society Hazardous to Your Brain Size?

Highlights: 

• For indigenous people, the brain regions associated with navigation grow larger with age, rather than shrink as with individuals from Britain. 
• Brain regions associated with higher-order cognitive function shrink faster in indigenous people. 

The Tsimane are a South American indigenous tribe who reside in the Bolivian Amazon and have little interaction with industrialized Bolivia. Neighboring the Tsimane are the Moseten, who are genetically and culturally similar to the Tsimane but have access to modern amenities such as running water, electricity, sanitation, medical services, and food markets. 

Compared to their counterparts in Western Europe and the United States, the Tsimane and Moseten are at lower risk for dementia, with less incidence of cardiovascular disease and type 2 diabetes. Furthermore, the Tsimane exhibit less overall brain shrinkage with age when compared to the Dutch, Americans, and Germans. 

Now, in a new study, USC scientists reveal that, with age, members of the Tsimane and Moseten tribes exhibit growth in certain brain regions when compared to healthy members of the British population. These findings suggest that the lifestyle of individuals in industrialized countries may contribute to brain deterioration and dementia. 

Brain Regions Associated with Navigation Dwindle and Don’t Grow with Industrialization 

The USC researchers compared the brains of the Tsimane and Moseten (T/M) with a segment of the British population less likely to be obese, smoke, drink alcohol, or have adverse health conditions. It was found that, compared to British males, the brain volumes of T/M males increased with age in regions associated with spatial navigation and visual processing. 

The growth of these regions may arise from the necessity for T/M men to navigate the complexity of the Amazon Rainforest. The same changes were not observed in females, perhaps due to T/M men engaging in more hunting, and traveling greater distances than T/M women. Still, T/M females exhibited increases in brain regions associated with memory, visual scene recall, and navigation when compared to their industrialized counterparts. 

Regions of the Brain that Shrink Slower in Industrialized Society 

When compared to healthy British people, T/M people exhibit faster atrophy with age in several brain regions. One of these regions is associated with higher-order cognitive functions, including impulse control, speech production, and planning. Another region is associated with audio-visual integration, consciousness, and emotional regulation. However, the authors note, 

“Ultimately, it may be difficult to measure cognitive functions in ways that are culturally invariant across the Tsimane/Moseten and US/EU. For this reason, exploring how the relationship between regional brain volume changes and cognitive functions differs between T/M and industrialized populations is challenging, particularly as T/M undergo societal changes.”

Is Modern Society Shrinking Our Brains?

One caveat to the study is that the researchers did not quantify industrialization. Still, we can assume that differences in brain volume between the British and T/M are attributable to lifestyle factors influenced by region and culture. Additionally, our brain is like our muscles, where the regions that are worked out the most get bigger and the ones used the least atrophy. 

Citizens of industrialized nations don’t necessarily need to use the navigation regions of their brains. Where most of the Amazon Rainforest may look the same to us, lacking obvious visual cues, most industrialized nations are littered with roads and signs, making them relatively easy to navigate. We also tend to go to the same places on a periodic basis (e.g. work, school, home, market), mitigating the need to learn new routes. 

On the other hand, indigenous tribes are relatively secluded from the outside world. They are not constantly inundated with information from the world’s network of industrialized nations. Their lifestyle is relatively simple, likely not requiring planning at each stage of life. Importantly, there are far less people, perhaps making relationships and social structures less complex. Moreover, they do not have to control their impulses when it comes to the conveniences of processed and fast foods. 

Importantly, the T/M, particularly the men, engage in physical activity, which has been shown to counteract cognitive decline and brain atrophy. The T/M also eat a diet rich in fiber, fruits, vegetables, and healthy fats typically associated with reduced brain atrophy. With that being said, it seems that much of the brain atrophy individuals of industrialized nations may experience can be explained by lifestyle choices.