Skip to main content
Move the World.
Do Bigger Brains Have Better Memories?

Lead Image © Orlando Florin Rosu

For many years, scientists believed that bigger brains (or more specifically, a bigger hippocampus) were associated with higher aptitude and that smaller brains were then necessarily a sign of lower aptitude, or even of cognitive decline when caused by a neurological disease like Alzheimer's. And even though some studies suggested that there might not be such a simple relationship, scientists were uncertain of what an alternative model might be. Until now. 

A study published in the journal Cerebral Cortex in December 2019 has, for the first time, demonstrated that it's not necessarily the size of the hippocampus that matters but rather how well it's connected to the brain's internal circuitry, through intact limbic white matter. In other words, the study suggests that cognitive decline could stem from a poor circuitry connection rather than a smaller hippocampus alone.

The Puzzle Pieces of Memory

The hippocampus is a small, seahorse-like piece of the brain, buried deep within the temporal lobe — the epicenter of all things learning and memory. Yet, despite its important role, the hippocampus's malleable and vulnerable exterior leaves it exposed to damage, including neurological and psychiatric disorders. In particular, the hippocampus has been observed to shrink in the brains of patients suffering from Alzheimer's.

Limbic white matter, on the other hand, is a little more difficult to point to directly. While a C-shaped bundle of nerves (called the fornix) is primarily responsible for transmitting signals to and from the hippocampus, the limbic system as a whole is a complex microstructure, which manages emotions, memories, and our senses.

Unravelling the Mystery

To study how these two pieces of the brain work together to affect memory and cognition, the team of researchers at Michigan State University looked at the brain scans of 337 older adults, roughly two-thirds male and one-third female, with an average age of 69-years-old. 

To determine their level of working memory, the subjects completed five sessions of memory recall tests, during which they were read the same list of 15 nouns and asked to write down as many as they could remember after each round. 

The research team then analyzed two different types of MRI scans — one of their hippocampus and one of their limbic white matter. The team observed that participants with both comparatively larger hippocampuses and uniform limbic white matter had stronger memory recall than subjects with either smaller hippocampuses or less uniform limbic white matter. Uniform, in this case, refers to the alignment of the limbic white matter's microstructure: white matter aligned in one direction (like the grain of a wood plank) appeared to better facilitate memory than white matter microstructure aligned in many different directions. This suggests that hippocampus size alone is not a sign of mental aptitude and that a shrinking hippocampus isn't necessarily an accurate biomarker for disease or age related cognitive decline. For example, a patient suffering from Alzheimer's could demonstrate signs of cognitive decline while still having a larger hippocampus if their limbic white matter microstructure was not uniformly aligned. According to the study's authors, these findings could lead to earlier diagnosis of age-related memory disorders for adults whose brain scans show a larger hippocampus. Because of their larger hippocampus, these adults are at-risk of having their "cognitive decline overlooked or mischaracterized if physicians do not also consider their white matter connectivity."

Gray Areas and Next Steps

While the study authors consider these results an "encouraging" step toward better understanding the brain's mysteries, they also write in the paper that they are far from foolproof. For example, the current study relied on limited timeframe and curated participant group (i.e. unimpaired and of similar ages). To address these lingering questions going forward the team suggests conducting a study over a longer period of time with a more diverse group of participants to see how these relationships change over time.

Up Next

Climate Crisis
Should We Genetically Engineer Carbon-Hungry Trees?
genetically modified trees
Climate Crisis
Should We Genetically Engineer Carbon-Hungry Trees?
Genetically modified trees that are designed to grow faster and store more carbon could help reverse climate change.

Genetically modified trees that are designed to grow faster and store more carbon could help reverse climate change.

Astronomy
Solar Probe Snaps Surprising Photo of the Surface of Venus
surface of venus
Astronomy
Solar Probe Snaps Surprising Photo of the Surface of Venus
The Parker Solar Probe has taken an image of the surface of Venus that may change what we thought we knew about the planet — or possibly the probe itself.

The Parker Solar Probe has taken an image of the surface of Venus that may change what we thought we knew about the planet — or possibly the probe itself.

Food
This Edible Sensor Can Alert You of Food Contamination
Food Contamination
Food
This Edible Sensor Can Alert You of Food Contamination
A microneedle patch made of silk changes color if it senses food contamination or spoilage, making it easier to know when food’s gone bad.

A microneedle patch made of silk changes color if it senses food contamination or spoilage, making it easier to know when food’s gone bad.

Medicine
Weird, Synthetic Intestinal Lining Could Make Treating Diseases Easier
Drug Delivery
Medicine
Weird, Synthetic Intestinal Lining Could Make Treating Diseases Easier
A synthetic intestinal lining could make it easier for doctors to control drug delivery and nutrient absorption in patients.

A synthetic intestinal lining could make it easier for doctors to control drug delivery and nutrient absorption in patients.

Prosthetics
Prosthetic Leg Uses AI to Adjust to Different Terrains
Prosthetic Leg
Prosthetics
Prosthetic Leg Uses AI to Adjust to Different Terrains
A new computer vision system developed to work with a prosthetic leg predicts the type of terrain ahead so that the limb can adjust accordingly.

A new computer vision system developed to work with a prosthetic leg predicts the type of terrain ahead so that the limb can adjust accordingly.

Drones
Underwater Drone Finds Wreckage of the “Unsinkable” USS Nevada
USS Nevada
Drones
Underwater Drone Finds Wreckage of the “Unsinkable” USS Nevada
More than 70 years after the U.S. military deliberately sank the “unsinkable” USS Nevada, researchers have located its final resting spot.

More than 70 years after the U.S. military deliberately sank the “unsinkable” USS Nevada, researchers have located its final resting spot.

Dispatches
CRISPR Edits Out Autistic Traits in Mice
CRISPR Edits Out Autistic Traits in Mice
Dispatches
CRISPR Edits Out Autistic Traits in Mice
The technique could also open up treatments for Huntington's, schizophrenia, and epilepsy.

The technique could also open up treatments for Huntington's, schizophrenia, and epilepsy.

New Space Race
How Do We Respond to Crimes in Space?
How Do We Respond to Crimes in Space?
New Space Race
How Do We Respond to Crimes in Space?
As talk of space colonization heats up, is it time to have a serious conversation about conflict resolution in a...
By Mike Riggs

As talk of space colonization heats up, is it time to have a serious conversation about conflict resolution in a place where few rules or laws exist?