New Scientist | 轻柔抚触对早产儿大脑有神奇作用​

小白老师说：今天的文章选自 New Scientist。New Scientist 是世界第一的科技新闻杂志，经常报道许多高端的科学项目，宣传科技活动，刊登专家公开演讲等。该杂志是英美国家的大学理工科学生必备杂志，也是全国医学博士英语考试阅读理解的重要题源。

文章关键词：

• premature 早产的
• premature baby 早产儿
• infant 婴儿
• respond 应答

Premature babies’ brains respond differently to gentle touching

By Linda Geddes

A gentle touch can make all the difference. Premature babies – who miss out on the sensory experiences of late gestation – show different brain responses to gentle touch from babies that stay inside the uterus until term. This could affect later physical and emotional development, but regular skin-to-skin contact from parents and hospital staff seem to counteract it.

Infants who are born early experience dramatic events at a time when babies that aren’t born until 40 weeks are still developing in the amniotic fluid. Premature babies are often separated from their parents for long periods, undergo painful procedures like operations and ventilation, and they experience bigger effects of gravity on the skin and muscles.

“There is substantial evidence that pain exposure during early life can cause long-term alterations in infant brain development,” says Rebeccah Slater at the University of Oxford.

But it has been less clear how gentle touches shape the brains of babies, mainly because the brain’s response to light touch is about a hundredth of that it has to pain, so it’s harder to study.

Gentle puff

Nathalie Maitre of the Nationwide Children’s Hospital in Columbus, Ohio, and her colleagues have gently stretched soft nets of 128 electrodes over the heads of 125 preterm and full-term babies, shortly before they were discharged from hospital. These were used to record how their brains responded to a gentle puff of air on the skin.

At the time of testing, the full-term babies were aged an average of 40 weeks – including both gestation and days post-birth – while the premature babies were tested at an average of 36 weeks.

The measurements revealed that babies born between 24 and 36 weeks of gestation were more likely to have reduced brain responses to gentle touch, compared with those born between 38 and 42 weeks. “Just because the receptors on the skin get activated doesn’t mean that the brain is processing a response,” Maitre says.

The more painful medical procedures a premature baby had endured, the less their brain responded to gentle touch later on – even though they had been given pain relief during such procedures.

However, brain responses to gentle touch were stronger among premature babies that had spent more time in physical contact with parents or hospital staff during their stay on the neonatal intensive care unit (NICU).

“These differences are to be expected to some extent,” says Francis McGlone at Liverpool John Moores University, UK. “We know that there are sensitive periods during early infancy, where what comes next in the development of the brain depends on what’s happened before.”

Beginnings of communication

It’s unclear whether the responses of preterm and full-term babies become more similar later on, or if they have an influence on how infants develop physically and socially. Touch and hearing are the first senses to develop, so much of how babies learn to communicate during their early months is through those senses.

“These experiences are the beginnings of communication and reciprocity,” says Maitre. “To have that be altered in any way is worrisome.”

While many premature babies experience pain, McGlone thinks that it is exposure to gentle touch that really matters. There’s mounting evidence that a set of nerves called c-tactile fibres are activated by soft caresses, and might provide a scaffold for the developing social brain. “These preterm infants have a highly developed c-tactile system, and I believe that the way the brain wires up its sense of self is critically dependent on this system feeding information in,” McGlone says.

A lack of gentle touches has been show to affect rat behaviour. Pups that aren’t licked grow up to be more aggressive and stressed. There’s also some evidence that people with autism process touch differently, and may struggle to understand the social significance of touch.

One recent study found that more than 25 per cent of babies born before 27 weeks of gestation develop autism, compared with 1 per cent of full-term babies – although prematurity exposes babies to many stressors besides just an altered experience of touch.

“The most interesting finding is that supportive touch – and here I only counted skin-to-skin touch, not holding or rocking – really seemed to make a difference,” Maitre says. “That’s extremely encouraging because if you’re a parent in the NICU, you feel incredibly out of control. It’s important to know that you are making a tremendous difference every time you touch your baby.”

Gentle contact with premature babies is likely to have other benefits too. A technique called “kangaroo care”, which involves skin-to-skin contact, has been linked to better weight gain in premature babies, and an improved ability to regulate their heart rate.

Journal reference: Current Biology, DOI: 10.1016/j.cub.2017.02.036