A new study has found that neurons in the brains of mice lacking the autism gene CNTNAP2 are unable to distinguish between social and nonsocial smells. The study’s findings suggest that these differences drive the social problems in the mice, and possibly in autistic people with mutations in the CNTNAP2 gene. The results of the study, which is one of the first to explore the way that neurons in the prefrontal cortex decipher social information, were published on November 25 in Nature Neuroscience. “We know from many studies that the prefrontal cortex is somehow important for social interactions,” lead author Ofer Yizhar said. “But we actually know very little about how social information is encoded.” In humans, mutations in the CNTNAP2 gene are connected to autism and language impairments, as well as altered brain connectivity. One prominent theory is that autism results from an imbalance between excitatory and inhibitory activity in the brain. Mice without the CNTNAP2 gene show that imbalance, though it is unclear if that is the source of their autism-like traits.
For their study, Yizhar and his colleagues recorded the electrical activity of neurons in the prefrontal cortex of male mice. The researchers exposed the mice to the social odors of unfamiliar male or female mice; the scent of peanut butter oil, which mice find attractive; the scent banana oil, which they are indifferent to; and the scent of the chemical hexanal, which they dislike. In mice with the CNTNAP2 gene, twice as many prefrontal neurons responded to the social odors as to the non-social ones. While the control mice were able to distinguish social and non-social smells, the mutant mice were unable to do so. For the next phase of their research, Yizhar and his team plan to see whether their findings hold true in other mouse models of autism. They are also testing whether boosting or silencing neuron activity in the prefrontal cortex will affect how that area of the brain processes social smells. Source: https://www.spectrumnews.org/news/mice-with-autism-mutation-may-be-indifferent-to-social-scents/