Cognitive ability, such as decision-making skills, varies wildly from person to person, and although it is acknowledged that both genes and the environment play a role in this variation, linking specific genes to healthy cognitive abilities has proven incredibly difficult. However, a new study published in the journal Nature Neuroscience reveals that a genetic network within part of the brain may indeed be the genes researchers have been looking for.
The team from Duke-NUS Medical School and Imperial College London (ICL) began their search by studying all active genes within the human hippocampus. This region of the brain is known to consolidate short-term memories into long-term ones, a key component of cognition, and thus provided a prime place to start their hunt. Using 122 frozen hippocampal samples taken from human patients displaying a range of cognitive abilities and neurological health statuses, the researchers compared and contrasted hundreds of genes with those also found in mice.
Instead of looking at how individual genes may be linked to specific neurological attributes, however, the team used a novel approach called System Genetics. In this approach, the researchers looked at the ways genes “interact” and determine how and when other genes are switched on or off. These gene networks would, overall, show a more complex influence on a subject’s neurological behavior than individual genes ever could in isolation.
Several common networks of genes were found – two of these, M1 and M3, appeared to show a particularly strong connection to human cognition, and in particular the consolidation of memory. In the case of M3, it was shown to contain 150 genes that appeared to work in tandem with each other in a “convergent” network; not only that, but this network would have been active straight from birth.
Importantly, this network was shown to be vital for two very different kinds of intelligence. The first, crystallized intelligence, is a person’s ability to adapt to situations involving patterns and behaviors they have encountered before; the second, fluid intelligence, determines how well a person can adapt to an entirely unique situation.
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The researchers also compared these gene networks with all known genetic data on neurodevelopmental diseases and disorders, including autism, epilepsy, and schizophrenia, and found that a third of the genes are mutated in patients that suffer from these conditions.
Although many of these genes were individually already connected to the development of these disorders, they have never been shown to be linked together in a network in this way before. Ultimately, the results of the study indicate that both healthy cognitive abilities and neurodevelopmental disorders are influenced by the behavior of the same genetic networks.
Michael Johnson, the lead author of the study, said in a statement that “it might be possible to work with these [networks] to modify intelligence, but that is only a theoretical possibility at the moment – we have just taken a first step along that road.”
This study reframes the way neurological development is perceived. The genetic network could be thought of as a team of chess pieces, with individual genes representing individual pieces. Although there are genes, or pieces, more important than some others, it doesn’t help to focus on just one: The strategy of the entire team needs to be taken into account.