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Do mice succumb to Mozart?
March 25,
2006
Special to World Science
The idea is at least as controversial today as it was when an
attention-grabbing 1993 study suggested it: listening to Mozart makes you smarter, at least temporarily.
Some researchers say the notion is outright debunked by now, though that hasn’t
shut down a booming industry in Mozart CDs marketed as brain-boosters.
Into this mess, a set of even more startling findings has crashed through the door.
Few if any people would claim rodents appreciate classical music, yet studies from three laboratories have found this much: Mozart does something for them.
The research found that a Mozart sonata improves maze performance in
rats and mice. Some findings also pointed to accompanying biochemical changes.
The studies have given a confidence boost to longtime proponents of the so-called “Mozart effect,”
who say the agreement of three “independent” studies starts to approach something that could be called rock-solid evidence. But with skeptics continuing to dispute the results, the only certainty is that the debate isn’t over.
Doubters point out that among other problems, rats and mice can’t even hear much of Mozart’s music. The pitches are too low for them.
“It’s important to approach these studies with a critical eye and not be dazzled by the big claims being made,” wrote Harvard University’s Christopher Chabris
in an email.
The 1993 study with humans reported that listening to 10 minutes of Mozart
boosted college students’ “spatial reasoning” abilities on tests for the next 10 to 15 minutes.
Attempts to replicate the finding gave mixed results. Chabris analyzed 16 studies and in 1999 concluded there was no “Mozart effect,” except possibly an improvement on one test involving ability to transform visual images, with even that result falling short of statistical significance.
Chabris attributed any effect to “enjoyment arousal” in his analysis, published in the Aug. 26, 1999 issue of
Nature, the same research journal that published the original finding. His work led to responses and counter-responses, along with contentions that the “Mozart effect” might last longer than originally reported.
As the debate raged, seeds of an even stranger finding had begun to sprout.
In the July 1998 issue of the journal Neurological Research, Frances Rauscher of the University of Wisconsin, Oshkosh, and colleagues reported a study in which rats were exposed to Mozart while in the womb and for 60 days after birth.
The rats completed a maze faster and with fewer errors than rats exposed instead to simpler music, silence, or a static-like noise, according to Rauscher, who had led the original study in humans.
Chabris and others disputed that report, too. But two more studies with similar results have appeared in scientific journals in recent months: one in the December 2005
Neurological Research and the other in the latest issue of Behavioural Brain
Research, dated May 15.
Both were designed to replicate Rauscher’s findings, with some key differences. The first omitted the in-uterus music exposure. The second studied mice instead of rats. Both found that the Mozart-exposed rodents made fewer errors on
mazes than others, though only the first study found that they also completed the
mazes faster.
“Continuous exposure to music during the perinatal [before-and-after
birth] period enhances learning performance in mice as adults,”
concluded the authors of the second, Sachiko Chikahisa and colleagues at Tokushima University in Tokushima, Japan.
They found the improvement was associated in increased levels of a molecule associated with “neural plasticity”—a
sort of flexibility in brain circuit wiring, believed to facilitate learning. The molecule, a protein, is called TrkB.
Thus, “at this time I would say there are two independent replications of my original” finding, wrote Rauscher in an email.
But Kenneth M. Steele of Appalachian State University in Boone, N.C., a past critic of
Mozart-effect findings, said the new studies also appear flawed. He said Chikahisa’s paper exhibits some wrong statistical techniques and some of the numbers presented suggest possible selective use of data.
Also, the data show the Mozart mice were on average “a little heavier than the other groups. This may indicate greater maturity,” Steele wrote in an email. Moreover, “this study suffers from the same flaw as the Rauscher
et al. study: lack of random assignment. The mothers were randomly assigned to a group. But the assignment of the offspring was determined by their mother.”
While Steele said he hadn’t yet read the study in Neurological Research in
full, he suggested its authors might not have been objective, having supported the Mozart effect
previously.
A major problem, he said, is that rats can’t even hear most of the notes in the Mozart music played in the studies, and mice
may hear none of them. Both animals’ hearing range only covers much higher pitches than human hearing does. Mice and rats are also born deaf, Steele added.
But Chikahisa and colleagues argued that mice can hear some of the higher pitches in the
music. Also, they wrote, “there are some studies that music influences behavior, brain function, immunity and blood pressure in rodents.”
Tokushima University’s Hiroyoshi Sei, one of the co-authors, said in an interview that mice
might feel vibrations of music without hearing notes.
Peter Aoun and colleagues at the MIND Institute of Costa Mesa, Calif., authors of the
Neurological Research study, wrote that rodents needn’t enjoy the music for it to have an effect. Some researchers have argued that certain music may
produce benefits simply by stimulating natural patterns of brain activity.
Sei said that to clarify such questions, he’s testing the effect of music on totally deaf mice.
He’s not sure, he added, what about the music may have influenced the rodents. But “it definitely something affects something in their behavior,” he said.
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