keep watching tv! What is the impact of technology on the developing brain? The coming of smartphones, Ipads, portable DVDs, and such has recently made this question a more pressing issue. More disturbingly, the age at which infants start watching TV has dropped from around 4 years to as early as 5 months. This has been accompanied by an increasing number of TV shows that target infants/children and an increase in time kids spend watching TV. Moreover, in contrast to how real life unfolds, these shows are usually rapidly paced and surreally sequenced. But how does this early sensory stimulation affect brain development? Is there a relationship between watching too much TV or overstimulation during infancy and later life behavioral and/or cognitive problems? To answer this question, Christakis et al (2012) developed a rodent model of overstimulation during early development. As depicted above, the researchers created an overstimulation chamber, which consisted of a standard mouse cage with mounted speakers and colored light sources at all four walls (first figure above). In order to mimic TV viewing, the scientists played audio clips from the Cartoon Channel and used a photorhythmic stimulator to chance colors and intensities in concordance with the audio for 6 hours a day, over 42 days. 10 days after the end of the overstimulation procedure, the researchers conducted a battery of behavioral tests on these animals and found that excessive audiovisual stimulation decreased anxiety-like behavior, increased risk-taking behavior, resulted in poorer short-term memory and impaired learning. Two of these parameters are shown above: the first being the elevated plus maze (EPM), which measures anxiety induced by open spaces as well as height, and the light-dark latency test (also called light-dark emergence test), a measure of risk taking and anxiety based on rodents’ innate aversion to brightly illuminated areas but also their competing exploratory interest. Compared to controls, overstimulated mice showed an increase in time spent in the open arms of the EPM, which is interpreted as them being less anxious, as well as increased time spent in the light chamber and reduced latency to enter the light chamber, which is interpreted as increased risk taking and exploratory behavior. Other findings not shown above include: *Increased time spent in the center of an open field (another test of anxiety and hyperactivity, as rodents prefer to move along the sides of a wall rather than be exposed out in the open) *Less time spent exploring a novel object *Less time on finding the escape hole on a Barnes maze, but increased errors trying to find the hole 3 days later, suggesting impaired learning and memory While the results of this study are captivating and informative, the project has limitations. For example, the researchers did not assess maternal behavior during this procedure so it is not possible to tease apart the contributions of maternal care and the overstimulation procedure on the later life behavioral and cognitive effects. Given that these animals were stimulated (as a litter) for 6 hours a day for over a month, it is conceivable that this procedure may have stressed the mother, which might have influenced the maternal care that the animals received. We also don’t know what behavior of the pups was like during this period of time. Also, the other grad student in our lab (shout out to Ro!) suggested that because lab rodents are typically NEVER exposed to excessive audiovisual stimulation, the results of this procedure in mice is likely to exert augmented effects than it would in humans.
Posted on: Fri, 23 Aug 2013 21:56:01 +0000
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