Several observational studies have suggested a possible link between children’s “screen time” in front of electronic media and the likelihood of developing attention deficit problems later in life. Unfortunately, there are practical and ethical problems with testing this correlation in a carefully controlled experiment with humans.
A new study in rodents, published February 17 in Scientific Reports, now provides new evidence that early stimuli similar to that provided by television and smart phones may lead to adult “distractibility.” The research team behind the Nature study was led by Abraham Zangen of Ben Gurion University of the Negev and included David Feifel, M.D., Ph.D., of UC San Diego, a 1995 and 1999 Young Investigator and 2004 Independent Investigator at UC San Diego.
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In their experiments, the researchers exposed one group of juvenile rats to a daily hour of interesting, changing odors (thought to be similar to the dynamic visual stimuli experienced by young children using electronic media), while other young rats were exposed to a non-changing mix of the same odors. This daily dose was delivered for five weeks—the equivalent in mouse-time of pre-puberty and adolescence in humans.
The scientists then tested the rats as adults, to see how well they performed on a common attention task. Adult rats exposed to the dynamic smell set as juveniles performed dramatically worse on the test when a distracting noise was added to the task, compared to animals that were exposed to the stable set of smells.
The dynamically-stimulated juvenile rats also had elevated levels of the growth factor protein BDNF in a the dorsal striatum, suggesting that there were neural changes in that part of the brain. Problems with cognition associated with attention deficits (specifically attention-deficit hyperactivity disorder, or ADHD) have been traced to that part of the brain in humans, the researchers say.
Dr. Feifel and his colleagues note that other studies of multisensory stimulation in young rodents seem to enhance rather than detract from brain development. They say more research is needed to discover what kinds of stimulation might be beneficial for the brain at an early age, information that might help to guide the development of electronic media for children.
Takeaway: Young rats exposed to a changing set of smells are more distractible as adults, according to a study that may have implications for whether children overexposed to electronic media develop adult attention deficits.