By all accounts Katie Joe McDonough was the least likely woman to rear progeny. She was independent, stubborn, and adventurous; nothing would hold her back. Her twenties were a thrill ‚?? packed with adventures to India and Nepal, learning French and moving overseas to work for a French oil company, the pursuit and completion of a PhD in Geophysics, and countless hiking, trekking, and boating trips. Katie Joe would not ‚??settle down.‚?? My Dad can attest to this ‚?? he barely got her through the chapel door. Pregnancy didn‚??t change anything ‚?? my mom was in denial for the first four months she was pregnant with me. But the day that I was brought naked and screaming into this world my Dad describes an incredible change that came over my mom. She softened. The minute her senses registered my existence all hesitance was gone. She became uncharacteristically tender. ‚??She got boring!‚?? my brothers and I describe with delight. She became a mother.
Evolution favors this kind of maternal transformation in new mothers ‚?? especially among mammalian females. As soon as the babies arrive, Mom‚??s senses must kick into overdrive. She now has much more to worry about than her own survival. She is now responsible for feeding, protecting, and teaching her offspring, and that takes a massive amount of increased brain function. Adi Mizrahi and his colleagues from the University of Jerusalem have begun to investigate some of these changes in the brains of mouse mothers. Through research on sensory integration between auditory and olfactory neurons in the brain, Mizrahi et al has uncovered evidence that suggests that specific brain plasticity is triggered in mouse females in response to their offspring. Sound familiar? I don‚??t know about yours, but my Mom can always tell when my hand is reaching into the cookie jar ‚?? even without turning around.
So what is responsible for this increased vigilance in new mothers? Mizrahi‚??s experiments demonstrate that in mouse mothers, specific sensory neurons exhibit increased plasticity in response to stimuli from mouse pups. This plasticity causes increased integration between sensory systems leading to hyper-vigilance in the mother. In the Mizrahi experiment, over 400 auditory neurons in new mouse mothers were tested for excitation in response to a variety of frequencies in the presence of (a) fresh air and (b) in the presence of their pups‚?? odor. Mizrahi‚??s findings demonstrate an overwhelming increase in the auditory neurons of new mothers in the presence of pup odor. In addition, the auditory neurons tested did not show the same increased responsiveness to neutral sounds. Instead increased activity in the neurons was triggered by the specific frequencies of mouse pup distress calls. This integrated response to pup calls and odors was not found in virgin female mice. But interestingly, the virgins did begin to show increased integration after prolonged exposure to mouse pups. This suggests that sensory integration plasticity in mice is not triggered by the actual act of birthing offspring, but may instead be linked to exposure to mouse pups. Maybe a similar phenomenon is responsible for the uncontrollable ‚??Awww!‚?? that pours from my mouth every time I see a picture of Jared Polis‚?? s new baby.