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Scientists raised zebrafish either alone or with their kin for different periods of time (Azul, Copyrighted free use, via Wikimedia Commons)

Impact of social isolation on the brain... of fish

Have you recently wondered how social-distancing and self-isolation may be affecting your brain? A research team led by the Max Planck Institute for Brain Research in Germany, working with the University of Exeter, discovered a brain molecule that functions as a “thermometer” for the presence of others in an animal’s environment. Zebrafish “feel” the presence of others via this brain function combined with water movements - which turns the brain hormone on.

Varying social conditions can cause long-lasting changes in animal behavior. Social isolation, for instance, can have devastating effects on humans and other animals, including zebrafish. The brain systems that sense the social environment, however, are not well understood. 

To probe whether neuronal genes respond to dramatic changes in the social environment, scientists raised zebrafish either alone or with their kin for different periods of time. The scientists used RNA sequencing to measure the expression levels of thousands of neuronal genes. Their results were published in the latest issue of Nature.

Lukas Anneser, the graduate student who led the experiments at the Max Planck Institute for Brain Research, said:“We found a handful of genes that were consistently changed in fish raised in social isolation. One of them wasparathyroid hormone 2 (pth2), a relatively unknown peptide in the brain. Curiously, pth2 expression tracked not just the presence of others, but also their density. When zebrafish were isolated, pth2 disappeared in the brain, but its expression levels rapidly rose, like a thermometer reading, when other fish were added to the tank.”.

Thrilled by this discovery, the scientists tested if the effects of isolation could be reversed by putting the previ