Shumyatsky and postdoctoral research collaborators Guillaume Martel and Akinori Nishi published their findings this week in the Proceedings of the National Academy of Sciences (PNAS) Early Edition online, and will be published in an upcoming issue of the PNAS print edition.
He contrasts the new findings with his earlier "fear gene" discovery, which focused solely on personal risk. "We now show that having less fear can profoundly change important behaviors for the survival of progeny and the species," he said.
The researchers conducted several experiments to rule out other reasons why the mutant mice were slow to retrieve pups. They ruled out diminished olfactory perception, as both normal and mutant mice located missing pups with equal speed using their sense of smell.
Both types of mice also equally passed object perception tests. The researchers then ruled out non-fear motivation, as both types stockpiled food with the expected urgency.
The one experiment that clinched fear-based motivation as the factor was when they "reminded" mice of their parental responsibility by first putting pups in the nest for five minutes before dispersing them. In this case, the mutant mouse retrieved pups as quickly as the normal mouse. This ruled out the possibility that mutant mice didn't retrieve pups because they lacked a fundamental knowledge of how to do it.
In the social behavior experiment, the mutant mice showed much less cautious behavior to other peers than did the normal mice. "The equivalent human behavior would be if a person hugged every stranger she met," said Shumyatsky. "In fact, that's something that humans with amygdalar damage might do they're very trusting."
The research adds further evidence to the amygdala's role in controlling innate fears specifically, the basolateral complex (BLA) of the amygdala. The BLA's role in forming memories for learned fear has been well-established, but its role
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