Baby cries reveal cocaine exposure in pregnancy
The cries of babies whose mothers used cocaine during pregnancy have a high-pitched vibration — 'hyperphonation' — in their voices.
A study conducted by researchers at the University of North Carolina School of Medicine provides the first known evidence of how a particular characteristic in the cries of some infants may be the result of prenatal cocaine exposure having modified their developing nervous system.
"These findings are important because identifying prenatal drug exposure in humans has been limited by our inability to identify nervous system damage caused by either maternal depression, or poor prenatal care, and/or a mother's drug use.
"The discovery of similar spectral characteristics in rat pup vocalizations after exposure to prenatal cocaine has proved useful for detecting the effects of cocaine — or similar drugs — on human brain systems."
Sandy Zeskind PhD, Levine Children's Hospital, Carolinas Medical Center, Charlotte, North Carolina, professor of psychology and pediatrics, University of North Carolina (UNC).
The study was conducted as part of the Cocaine Affects Mother-Infant Dyads (CAMID) research initiative. CAMID's principal investigator, Josephine M. Johns PhD, professor of psychiatry and psychology at UNC, is senior author of the PLOS ONE paper. CAMID research has focused on how drug abuse affects mother-infant relationships on multiple levels.
Previous work by Zeskind and others has shown how a high-pitched spectral characteristic in an infant's cry — called "hyperphonation" — may show that a newborn has suffered nervous system damage due to prenatal drug exposure. This will be true even when a baby otherwise appears to be perfectly healthy by pediatric examination.
Hyperphonated cries are more urgent, excited, distressed and sick sounding than normal baby cries. They elicit a rise in heart rate in some or a heart rate decline in others. They also tend to induce sweat on the skin of the baby's care givers and generally impress all who hear with how "sick" the baby sounds. The variability in pitch of these cries may reflect an infant's inability to control of its' own voice and perhaps neural disorganization in general. (The Evolution of Emotional Communication; edited by Eckart Altenmüller, Sabine Schmidt, Elke Zimmermann)
Similar in pitch and structure to an infant's hyperphonation are the ultrasonic vocalizations of rat pups born with prenatal cocaine exposure. This experiment was one of the first to find drug exposure affecting humans and rodents in a similar way. It also highlights the goal of CAMID to join basic laboratory research with clinical research in order to quickly initiate clinical interventions for unhealthy infants.
Spectral and temporal features of human infant crying may detect neurobehavioral effects of prenatal cocaine exposure (PCE). Finding comparable measures of rodent ultrasonic vocalizations (USVs) would promote translational analyses by controlling the effects of correlated variables that confound human studies. To this end, two studies examined the sensitivity of similar acoustic structures in human infant and rat pup vocalizations to effects of PCE. In Study 1, cry sounds of 107 one month-old infants were spectrum analyzed to create a novel set of measures and to detect the presence of hyperphonation - a qualitative shift to an atypically high fundamental frequency (basic pitch) associated with neurobehavioral insult. Infants with PCE were compared to infants with prenatal polydrug-exposure (PPE) without cocaine and with infants in a standard comparison (SC) group with no prenatal drug exposure. In Study 2, USVs of 118 five day-old rat pups with either PCE, prenatal saline exposure or no prenatal exposures were spectrum analyzed to detect the presence of frequency shifts – acoustic features that have a frequency waveform similar to that of hyperphonation. Results of study 1 showed PCE had two sets of sex-dependent effects on human infants: PCE males had higher pitched cries with more dysphonation (turbulence); PCE females had longer pauses between fewer cry sounds that were of lower amplitude than comparison groups. PCE and PPE infants had more cries with hyperphonation than SC infants. In study 2, PCE pups had a greater percentage of USVs with shift in the acoustic structure than pups in the two control groups. As such, the novel measures of human infant crying and rat pup USVs were sensitive to effects of PCE. These studies provide the first known translational analysis of similar acoustic structures of vocalizations in two species to detect adverse effects of prenatal drug exposure.
This latest research is funded in part by the United States National Institute on Drug Abuse and National Institute of Mental Health.
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