The humanized gene actually improved the animal’s behavior rather than messing up the system.
According to a new study, mice that receive a human version of a speech and language gene display accelerated learning. Don’t expect these findings to lead to a rush of smarter, “uplifted” animals—though they might just reveal something new and fascinating about the evolution of human speech and language.
The gene for the protein called FOXP2 has been firmly linked to human speech and language. Humans with just one functional copy of this gene experience difficulties in learning and struggle with spoken and written language. The gene itself is not unique—chimps have a version of it. But because the human and chimpanzee lineages diverged roughly 6 million years ago, they don’t have two key changes in amino acids that humans have evolved.
To learn more about how FOXP2 alters the brain, scientists genetically engineered mice with the human form of FOXP2. In experiments with these rodents, the researchers focused on two modes of learning thought to be crucial for speech and language—declarative learning, which involves knowledge learned consciously, and procedural learning, which involves knowledge learned by experiencing something enough times for it to become habit.
The researchers had mice run through a maze to get a reward of chocolate milk. The animals could figure out the location of the reward either through sensory cues such as rough or smooth floors, which corresponds to declarative learning. Or, they could discover the reward was always linked to either a left or right turn, which corresponds to procedural learning. The investigators discovered the mice with the human form of FOXP2 learned profoundly faster than regular mice when both declarative and procedural forms of learning were involved. The scientists detailed their findings in the Proceedings of the National Academy of Sciences.
“What surprised me most was that the humanized gene actually improved the animal’s behavior rather than messing up the system,” says behavioral neuroscientist Kyle Smith at Dartmouth College, who did not take part in this research.
Declarative learning involves circuits in the central part of the striatum region of the brain, while procedural learning involves circuits in more peripheral parts of the striatum. The scientists found that both sets of circuits were altered in the mice with the human form of FOXP2.
Prior studies found that mice with the human version of FOXP2 demonstrate profound changes in the chemistry and anatomy of brain circuits essential for acquiring habits and other physical and mental behaviors, such as songbirds learning song. The kinds of changes seen in these studies may once have helped the human brain evolve speech and language.
“I don’t think the goal is to make smarter animals, but rather to dissect out the biology underlying smartness,” Smith says. “Having said that, if we can find a procedure like this that would help treat neurological or psychiatric disorders, that would be a wonderful purpose. For example, Parkinson’s disease involves the same brain circuits being studied in this article — perhaps genes could be tweaked in similar ways to help.”
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