Researchers Hear Mouse 'Songs'
Everyone knows that mice squeak and squeal, but few realize that mice also communicate in the ultrasound range, at frequencies far higher than the human ear can detect.
Now scientists conducting the first detailed analyses of those vocalizations have concluded that these sounds are much more than a high-pitched version of the simple hisses and grunts produced by many other animals. Rather they are complex patterns of chirplike syllables that meet the scientific definition of "song."
Indeed, conclude Timothy Holy and Zhongsheng Guo of Washington University School of Medicine in St. Louis, reporting in the December issue of the journal PLoS Biology: "The richness and complexity of mouse song appear to approach that of many songbirds."
If confirmed, the work means mice are members of an elite club that includes only three other mammals: humans, whales and bats.
The two researchers recorded the inaudible sounds with a high-frequency microphone. After filtering out unwanted noises -- including persistent squeaks and gnawing sounds -- they used a computer program to bring the calls down to the range of human hearing.
The syllables and sweeping arcs of pitch, which sound very much like bird songs, fulfill commonly accepted definitions of "song," which require that multiple syllable types be strung into phrases of recognizable sequences or motifs.
(They can be heard at http://biology.plosjournals.org/archive/1545-7885/3/12/supinfo/10.1371_journal.pbio.0030386.sa002.wav)
Comparative studies indicated that -- as with birds, which develop personal styles close to those of the mentors who taught them -- individual mice sing their own versions of songs. But it remains unclear whether mice learn to sing or are born with the talent.
The team also found preliminary evidence that mice can produce two sounds simultaneously from separate parts of the larynx, perhaps explaining how they produce overlapping tonal transitions.
So far, only the mice know why they are singing. Ongoing experiments aim to see whether males sing differently around the scent of females, which might point to courtship as a motivation.
The team speculates that generations of inbreeding and captivity may have reduced the richness of mouse song. If so, they write, wild mice may have even more interesting repertoires.
-- Rick Weiss
No Adverse Effects in Peyote Use
Repeated use of the hallucinogenic drug peyote produces no psychological problems or adverse effects among Navajos who use it in religious rituals, according to an unusual study partly funded by the National Institute on Drug Abuse.
Those who ingested the peyote cactus in fact had better moods and a greater sense of psychological well-being than nonusers, although those benefits probably were the result of being part of a close-knit religious community rather than a result of the hallucinogen, researchers who conducted the study found.
The scientists cautioned that it is unclear whether people who use hallucinogens illegally would show similar benefits. Navajo users are allowed to ingest the drug as part of a religious ceremony, and its use is carefully circumscribed and guided. The active ingredient in peyote is the drug mescaline.
"Something being used responsibly in a religious setting in a ceremony that is more than a century old is different than an illicit user taking something on the street," said Harrison Pope, one of the study's authors. "We cannot generalize from these findings."
Previous studies had suggested that hallucinogens caused lasting psychological problems, but Pope, a professor of psychiatry at Harvard Medical School, said the new study is the first to study users who were not simultaneously abusing other drugs. The Navajo peyote users are forbidden from using drugs outside the religious ceremonies.
"In the '60s and '70s, there was negative commentary about hallucinogens, with statements saying these were toxic drugs that could cause people to become insane," said Pope, whose paper was published last week in the journal Biological Psychiatry.
"The Navajos had told us they had not noticed any problems," he added. "They had seen numerous members of the church [use peyote and] it was not something anyone had observed to be a problem."
The researchers compared Navajos who had ingested peyote at least once a month over a long period with Navajos who were not taking any drugs. A series of tests involving spatial skills and strategic reasoning showed no difference between the groups.
-- Shankar Vedantam