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Friday, December 13, 2013
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Many more messages in baby’s cry
A newborn’s cry can signal more than whether she is hungry or tired.
Subtle differences in infant wailing can provide important clues to later developmental and neurological conditions, such as poor language acquisition. Cry characteristics may also give hospitals a way to assess pain when treating babies. Down the road, researchers hope cry analysis may help doctors detect conditions and start treatment earlier.
Researchers at Brown University and Women & Infants Hospital in Providence have devised a computer program to help analyse a baby’s cries. They hope to soon make it available to researchers world-wide looking to analyse crying patterns that can’t always be detected by the human ear.
The computer program breaks down cries into 12.5-millisecond frames and measures the pitch and volume, among other parameters. In total, it can evaluate 80 different parameters, which could help detect risk for conditions affecting a newborn baby’s health.
Because a cry is controlled by cranial nerves, it can be a window into the brain. While researchers haven’t reached the stage where they can link cry characteristics with specific conditions, they’ve found that, on a group level, an infant’s nervous system and therefore cry can be affected by prenatal exposure to alcohol, birth injuries, and even related to later diagnoses of autism.
Researchers aren’t at the stage where cries can pinpoint specific illness, although that is the ultimate goal. Today, a baby’s cry can be tapped for information on pain and the nervous system.
In the 1960s researchers began evaluating baby’s cries in relation to the disorder Cri du chat, French for the cry of the cat. Babies with the rare genetic disorder have a very distinct and high-pitched cry discernible to the human ear.
Pitch is number of times the vocal chords vibrate per second. A normal baby’s cry pitch is about 400 hertz (cycles per second). A baby with Cri du chat, on the other hand, would have one of 1,000 hertz or higher.
A new computer program devised by researchers in Providence, RI, breaks down a baby’s cries in myriad ways. The top panel shows a cry’s pitch, or frequency. The second plots additional frequency characteristics of the cry, called formants. The third shows how clear the cry sound is, a phenomenon known as “voicing” or “phonation.” The final panel is a measure of the energy or loudness of the cry.
While researchers have evaluated cries with more labour-intensive systems in the past, the Brown researchers say the automated analyser will result in a more detailed and faster process.
Philip Sanford Zeskind, director of neurodevelopmental research at Carolinas HealthCare System’s Levine Children’s Hospital in Charlotte, NC, said analysing a baby’s cry is especially pertinent during the first two to three months before a baby picks up on social cues (ie: cry and mommy will come running).
“We can start right at birth,” said Dr Zeskind. “The analysis of crying can tell you if there’s something wrong with the baby’s nervous system even in the absence of routine signs on physical and neurological exams.”
His research has found that even healthy babies born full-term and with normal neurological exams can have cries indicating something is wrong with the nervous system due to prenatal alcohol exposure. Those findings from a small study were published in a 1996 article in the journal Infant Behaviour and Development.
A cry’s pitch is controlled by the brain stem and a complex of cranial nerves that goes out of the brain stem and to the muscles associated with the larynx. “When listening to the pitch of a cry what you’re really doing is listening to the brain stem,” Dr Zeskind said.
A cry can communicate information on how a baby gets aroused and how much sensory stimulation affects him. “Babies with the high-pitched cries very frequently have other signs that their nervous system gets easily stressed or overstimulated,” he said.
Barry Lester, a professor of psychiatry and paediatrics at the Warren Alpert Medical School of Brown University, said any digital recorder with taped cries can be plugged into the computer system. The computer reads it and breaks it down and does a series of computations to analyse the cry in various ways.
Characteristics that can be measured include pitch variability, time between cries, and how long they last. Dr Lester developed the program with Stephen Sheinkopf, assistant professor of psychiatry and paediatrics at Brown, and Harvey Silverman, an engineering professor at Brown.
In a 2012 article in the journal Autism Research, Drs Sheinkopf and Lester and other researchers examined the acoustic characteristics of infant cries in babies at risk for autism compared with those that weren’t. Cry samples were obtained from 21 6-month-old infants at risk for autism spectrum disorder compared with 18 low-risk infants. They found that at-risk infants had higher pitched cries with a more variable frequency.
The researchers concluded that there was preliminary evidence that “disruptions in cry acoustics may be part of an atypical vocal signature of autism in early life.”
Determining pain in a newborn is another possible use, Dr Sheinkopf said. “One challenge for hospital staff is to actually measure and monitor pain,” he said. “Pain-related cries may be different than non-pain-related cries in a way that could be useful for doctors to monitor the status of babies” after procedures.
Pain cries usually have a considerably longer pause between the first and second utterance. The first utterance is also usually louder and longer because the baby has to let out so much air, so it can last four to five seconds or more, as opposed to two or three.
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