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

Animals
Bomb Detectors Record Rare Pygmy Blue Whales Singing
pygmy blue whales
Animals
Bomb Detectors Record Rare Pygmy Blue Whales Singing
Underwater microphones used to listen for signs of nuclear bomb testing have captured the singing of a population of rare pygmy blue whales.

Underwater microphones used to listen for signs of nuclear bomb testing have captured the singing of a population of rare pygmy blue whales.

Climate Crisis
Can Seaweed Save the Planet?
carbon offsets
Climate Crisis
Can Seaweed Save the Planet?
A Maine startup is growing vast quantities of seaweed and then burying them at the bottom of the ocean to sequester carbon for carbon offsets.

A Maine startup is growing vast quantities of seaweed and then burying them at the bottom of the ocean to sequester carbon for carbon offsets.

The Brain
Brain Mapping: Explained
brain mapping
The Brain
Brain Mapping: Explained
The brain is a difficult place to work. How can brain mapping help open the black box between your ears?

The brain is a difficult place to work. How can brain mapping help open the black box between your ears?

Dinosaurs
This Digital Dinosaur Brain Has Some “Quite Surprising” Insights
dinosaur brain
Dinosaurs
This Digital Dinosaur Brain Has Some “Quite Surprising” Insights
The Bristol dinosaur is like a mini-Brontosaurus, a four-legged plant eater. Or so we thought; a new digital dinosaur brain may change what we know about the dino.

The Bristol dinosaur is like a mini-Brontosaurus, a four-legged plant eater. Or so we thought; a new digital dinosaur brain may change what we know about the dino.

Oceans
Divers Remove Wildlife-Killing “Ghost Nets” From Shipwreck
Ghost Nets
Oceans
Divers Remove Wildlife-Killing “Ghost Nets” From Shipwreck
The Healthy Seas initiative removes wildlife-killing “ghost nets” from the ocean so that they can be recycled into useful Econyl yarn.

The Healthy Seas initiative removes wildlife-killing “ghost nets” from the ocean so that they can be recycled into useful Econyl yarn.

3D Printing
The World's First Floating 3D Printed House
3D Printed House
3D Printing
The World's First Floating 3D Printed House
A group in the Czech Republic is using a 3D printing robot to construct what it claims will be the world’s first floating 3D printed house.

A group in the Czech Republic is using a 3D printing robot to construct what it claims will be the world’s first floating 3D printed house.

Medical Breakthroughs
New Evidence of Memory Consolidation While We Sleep
Memory Consolidation
Medical Breakthroughs
New Evidence of Memory Consolidation While We Sleep
Thanks to brain implants, scientists have the first direct evidence of “offline replay” in humans, a process thought to be key to memory consolidation.

Thanks to brain implants, scientists have the first direct evidence of “offline replay” in humans, a process thought to be key to memory consolidation.

Criminal Justice
Algorithm Clears Thousands of Marijuana Convictions in Just One Minute
criminal record clearance
Criminal Justice
Algorithm Clears Thousands of Marijuana Convictions in Just One Minute
With this new system that identifies candidates for criminal record clearance and even auto-fills forms, offenders don’t even need to apply.

With this new system that identifies candidates for criminal record clearance and even auto-fills forms, offenders don’t even need to apply.

Animals
The Real Mother of Dragons
Real dragons
Watch Now
Animals
The Real Mother of Dragons
Meet the scientists using dragon blood to fight superbugs
Watch Now

If you thought dragons existed only in the domain of historical fantasy fiction like Game of Thrones or Lord of the Rings, think again. Dragons are real and their blood just may be our biggest hope when it comes to tomorrow's antibiotics. Dragons Are Real The largest of any earthly lizard, Komodo dragons walk the earth to this day. They’re not only real, but they’re also much like their larger, fictional counterparts, fit...