According to the scientists, the young rats used in their study were exposed to constant white noise that is relevant to the increasing, random noise encountered by humans in today's environment. They theorize that their findings could aid in explaining the increase in language-impairment developmental disorders over the last few decades.
The researchers, which included Howard Hughes Medical Institute medical student fellow Edward Chang and otolaryngology professor Michael Merzenich at the University of California at San Francisco, published their findings in the April 18, 2003, issue of the journal Science.
"While the rat is not a perfect model of human auditory development, it does allow us to investigate the fundamental role of early sensory experience in mammalian auditory development," said Chang. "For example, we do know that exposing infant rats to specific sound stimuli can induce long-standing representational changes in the brain. Other researchers have shown that there are striking parallels in humans and other animals."
Although past experiments have demonstrated the important effects that visual experience can have on brain development in animals and humans, Chang said very few comparable experiments have been reported that explore the effects of patterned early auditory experience on cortical development.
"Auditory experience is clearly an important factor in humans for learning language," he said. "We learn to speak and read through our sensitivities to speech sounds that are heard during early life."
Thus, Chang and Merzenich designed experiments in which they reared rat pups in an environment of moderate continuous background noise, which, while not injurious to their per
Contact: Cindy Fox Aisen
Howard Hughes Medical Institute