Do bigger brains have better memories?

Do bigger brains have better memories?

New York, March 2, 2020

For many years, scientists believed that larger brains (or more specifically, a larger hippocampus) were associated with higher aptitude, and that smaller brains were inevitably a sign of lower aptitude, or even a cognitive decline, if they were caused by a neurological Disease like Alzheimer’s can be caused. And although some studies have suggested that there may not be such an easy relationship, the scientists were unsure of what an alternative model might be. Until now.
A study published in December 2019 in the journal Cerebral Cortex showed for the first time that it is not necessarily the size of the hippocampus that is decisive, but rather how well it is connected to the internal circuits of the brain via the intact limbic white matter. In other words, the study suggests that the cognitive decline may be due to deteriorating circuit connections rather than a smaller hippocampus alone.
The puzzle pieces of memory
The hippocampus is a small, seahorse-like piece of the brain that is buried deep in the temporal lobe – the epicenter of everything related to learning and memory. Despite its important role, the hippocampus is vulnerable to damage, including neurological and psychiatric disorders, due to its malleable and vulnerable appearance. In particular, it has been observed that the hippocampus in the brain of Alzheimer’s patients shrinks.
The limbic white matter, on the other hand, is somewhat more difficult to grasp directly. While a C-shaped bundle of nerves (called Fornix) is primarily responsible for signal transmission to and from the hippocampus, the limbic system as a whole is a complex microstructure that manages emotions, memories and our senses.
Decipher the secret
To investigate how these two parts of the brain work together to affect memory and cognition, the research team at Michigan State University examined the brain scans of 337 older adults, about two-thirds of whom are male and one-third female, and an average age of 69 Years.
To determine the level of their working memory, the subjects completed five sessions of memory test tests, in which they were read the same list of 15 nouns and asked to write down as many as they remembered after each round.
The research team then analyzed two different types of MRI scans – one from their hippocampus and one from their limbic white matter. The team observed that participants with both a comparatively larger hippocampus and uniform limbic white matter had a stronger memory than people with a smaller hippocampus or less uniform limbic white matter. Uniform in this case refers to the orientation of the microstructure of the limbic white matter: white matter, which is oriented in one direction (like the grain of a wooden board), seemed to promote memory better than the microstructure of the white matter, which is used in many different ways Directions. This suggests that the size of the hippocampus alone is not a sign of intellectual suitability, and that a shrinking hippocampus is not necessarily an accurate biomarker for disease or age-related cognitive decline. For example, a patient with Alzheimer’s could show signs of cognitive decline while still having a larger hippocampus if his limbic microstructure of the white matter is not aligned uniformly. According to the study’s authors, these findings could lead to an earlier diagnosis of age-related memory disorders in adults whose brain scans show a larger hippocampus. Because of their larger hippocampus, these adults are at risk of „missing cognitive decline or being mis-characterized unless doctors consider their white matter connectivity“.
Gray areas and next steps
While the study’s authors regard these results as an „encouraging“ step towards better understanding of the brain’s secrets, they also write in the paper that they are far from foolproof. For example, the current study was based on a limited time frame and a curated group of participants (i.e. undamaged and similarly old people). To resolve these outstanding issues in the future, the team suggests doing a long-term study with a more diverse group of participants to see how these relationships change over time.