Genes, Intelligence, and Size of Brain Structures

Smarter People Have Bigger Brain Structures (Thanks to their Genes)

A large network of neuroscientists and doctors that compared over 30,000 brain images with people’s DNA says it’s found several genes that appear to influence the size of brain structures involved in intelligence and memory, as well as the volume of the brain itself. __
More on genes and brain size

Revolutionary advances in brain imaging and genomics are allowing neuroscientists to confirm what students of HBD have been saying all along: Genes influence both brain sizes and human intelligence.

In one of the largest research undertakings of its kind, a team of geneticists and neuroscientists has uncovered a number of genetic variations that influence the size of some key brain structures, including the hippocampus and the putamen. The result may advance understanding of such devastating neurodegenerative diseases as Alzheimer’s, Parkinson’s and Huntington’s.

Their findings, reported Wednesday in the journal Nature, identify five novel genetic variants that appear to influence the size of two structures in the brain’s basal ganglia–the putamen and caudate nucleus–that help govern the initiation and control of learned movement.

The study also confirmed earlier research locating a site on the genome that affects the brain’s overall volume, and another that influences the size of the hippocampus, a key structure in the formation and retrieval of memories.


Earlier debate over brain size and intelligence was limited by scientists’ inability to look inside the brain and measure all its structures and connections — for making comparisons with measured IQ. That is no longer a problem.

The volume of certain brain structures is likely to be an important measure of those structures’ ability to function properly and fight off disease, said Thompson. With aging, for instance, many of the structures found to be influenced by genes lose volume, and that appears to make them vulnerable to disease, he added. __ Genes, Brain Size, Brain Function

The volumes of certain key brain structures have been linked to IQ. Coincidentally, the volumes of these brain structures are also under genetic control.

The two seahorse-shaped structures tucked deep inside the brain on both sides, left and right, are referred to as the hippocampus. As part of the limbic system, the hippocampus plays a role in both emotion and the formation of new memories. Specifically, the hippocampus is where information — usually emotionally-charged information — is transferred, like some hasty transaction performed at the ATM, into the long-term memory banks. While the left hippocampus appears to help us retain words and language, the right hippocampus is linked to spatial memory, such as the layout of streets in your hometown. __

Despite the claims of blank-slaters, smarter brains have been programmed genetically to have specific larger parts, with better and faster connections between brain locations.

Structurally, genetic influences explain 77–88% of the variance in the thickness of the mid-sagittal area of the corpus callosum, the volume of the caudate nucleus, and the volumes of the parietal and temporal lobes.[3] __ Deary, I. J., Penke, L., & Johnson, W. (2010). The neuroscience of human intelligence differences. [Review]. Nature Reviews Neuroscience, 11(3), 201–211 via Wikipedia

… More on basal ganglia volumes and intelligence … (Remember that basal ganglia volumes and many other volumes and characteristics of specific grey and white matter components of the brain, are largely genetically determined.)
More on genes and brain size

Recent research at the Cleveland Clinic confirms an association between larger hippocampi and better memory — particularly spacial memory.

When brain structures called hippocampi are smaller, that may point to a higher risk of getting Alzheimer’s disease and other types of dementia, new research suggests. People who did better on certain memory tests tended to have larger hippocampi.

In this latest study, published in Alzheimer’s Research and Therapy, researchers recruited 226 people attending memory clinics. Thirty-four participants had Alzheimer’s disease, 95 had MCI, 25 had normal memory (for their age), and the remainder (72) had neurological disorders, including other types of dementia.

… “We’ve known for some time that the hippocampus is a key area of the brain susceptible to damage in Alzheimer’s disease, and this research links the size of the hippocampus to a person’s performance on different types of memory test(s),” says Dr. Laura Phipps of Alzheimer’s Research UK. __

Larger hippocampi result partially from genetic programming and gene expression. But the hippocampus is also one of the brain sites where new nerve cells are born throughout a person’s lifetime. In other words, up to a certain level of damage or degeneration, the hippocampi possess neuronal plasticity.

Publications from the ENIGMA Brain Consortium, providing more research depth on brain volumes, genes, intelligence, and disease.

The exquisite control that genes exert over brain function:

But new genomic research reveals that, at an even deeper level, emotions and behavior are also shaped by a second layer of organization in the brain, one that we only recently created the tools to see. This one relies on genes.

Putting all of this information together, we can see that our genes and gene expression are far more important to behaviours and cognition than ever imagined. Populations with varying genetic histories are apt to possess different cognitive aptitudes and behavioural peculiarities.

This is likely why prototypical profiles of behaviour and cognition tend to vary between populations that evolved in different parts of the world. Their genomes and modes of gene expression (including epigenetic mechanisms) evolved differently in the face of different environmental challenges.

The quest to understand the human brain — in all of its varieties and manifestations — is an exciting adventure which should never be held back by political concerns or a suicidal political correctness. The future demands all that we can give it.

Better understanding the brain

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