A 'touching sight': How babies' brains process touch builds foundations for learning

January 16, 2018 by Kim Eckart, University of Washington
These images illustrate two views of the left hemisphere of the brain. Image A shows the location where infants in the experiment processed a touch to the hand; image B shows where, in the brain, they processed a touch to the foot. Credit: UW Institute for Learning & Brain Sciences

Touch is the first of the five senses to develop, yet scientists know far less about the baby's brain response to touch than to, say, the sight of mom's face, or the sound of her voice.

Now, through the use of safe, new brain imaging techniques, University of Washington researchers provide one of the first looks inside the infant's brain to show where the sense of touch is processed—not just when a baby feels a touch to the or foot, but when the baby sees an adult's hand or foot being touched, as well.

The evidence of activity in the somatosensory cortex for both "felt touch" and "observed touch" shows that 7-month-old have already made a basic connection between "self" and "other," which researchers say lays the groundwork for imitating and learning from the behavior of other people, and for empathizing with them.

The findings by the UW Institute for Learning & Brain Sciences (I-LABS) are published this week in Developmental Science.

"Long before babies acquire spoken language, touch is a crucial channel of communication between caregivers and babies," said the study's primary author, Andrew Meltzoff, UW psychology professor and co-director of I-LABS. "Now we have the tools to see how the baby's body is represented in the baby's brain. This allows us to catch the first glimpse of a primitive sense of self that provides a building block for social learning."

Past studies investigated how infants' brains respond to touch, generally. The authors believe this is the first experiment to measure the specific networks of the brain where this processing occurs, and to illuminate how babies' brains respond to seeing another person being touched, in the absence of being touched themselves.

For the study, researchers used the I-LABS Magnetoencephalography (MEG) machine to capture images of brain activity in 7-month-old infants as they were touched on the hand and foot, and as they watched videos of an adult hand and foot being touched.

Researchers were particularly interested in the brain's somatosensory cortex, a region generally described as a strip of tissue in the brain that runs between the ears, over the top of the head. It is in this region, in separate places and at different levels of strength, that the brain processes touch to different parts of the body. A touch to the hand, for example, is a stronger sensation - and is processed in a different location along the somatosensory cortex - than a touch to the foot.

In the first experiment, each infant was seated in the MEG to measure brain activity as they received light touches. A small, inflatable balloon-like device was placed on the top of the baby's hand, and when it expanded and contracted according to a computer-controlled timetable, it produced light taps on the baby's skin. The same procedure was followed for the top of the baby's foot.

The data showed that, when the hand was touched, the hand area of the somatosensory cortex was activated in all 14 infants tested; when the foot was touched, activation occurred in the foot area of the brains of all of the infants but one.

A different group of infants provided data for the "observed touch" experiment, in which they also were seated in the MEG but watched separate videos of an adult hand and an adult foot being touched by a small rod. Researchers discovered that the infants' own somatosensory cortex (the "touch center" in the baby brain) also became activated when the babies simply observed someone else being touched.

There was a weaker response to "observed touch" than to "felt touch," which was expected, Meltzoff said. The same is true of adults: A touch to your own hand is going to generate greater in the than merely seeing the touch to someone else's hand.

The key, Meltzoff pointed out, is that the same part of the infant's brain registered both kinds of touch, indicating a baby's capacity for recognizing the similarity between their own body parts and those they see in other people.

This new evidence for shared neural regions processing touch to self and to others makes sense, Meltzoff said. As parents know, babies watch and imitate what adults do. Imitation is a powerful learning mechanism for infants, but in order to imitate, infants have to perceive how body parts correspond. In other words, they need to reproduce the same movement with the same part when they imitate what their parent is doing. Scientists have wondered how infants make this connection. "Before they have words for the , babies recognize that their hand is like your hand, and their foot is like your . The neural body map helps connect to other people: The recognition that another person is 'like me' may be one of the baby's first social insights," Meltzoff explained.

With development, this "like-me" recognition eventually flowers into feeling empathy for someone else. If you see someone accidentally hit their thumb with a hammer, you rapidly, if perhaps imperceptibly, recoil by moving your hand. This is where a shared neural body map that connects self to other comes into play.

Further research could use the MEG to investigate how infants develop more sophisticated body awareness as they grow older, the paper notes.

"The idea of using science to study how and when humans first feel a sense of connectedness with others is important and fascinating," Meltzoff said. "We can now look under the hood and see what's happening when a baby watches and connects to others. It's a touching sight."

Explore further: Baby brains are tuned to the specific actions of others

More information: Andrew N. Meltzoff et al, Infant brain responses to felt and observed touch of hands and feet: an MEG study, Developmental Science (2018). DOI: 10.1111/desc.12651

Related Stories

Baby brains are tuned to the specific actions of others

October 30, 2013
Imitation may be the sincerest form of flattery for adults, but for babies it's their foremost tool for learning. As renowned people-watchers, babies often observe others demonstrate how to do things and then copy those body ...

Researchers pioneering research on 'body maps' in babies' brains

September 8, 2015
For more than half a century, scientists have studied how the surface of the body is mapped in parts of the brain associated with touch.

A prescription for touch: Early experiences shape preterm babies' brains

March 16, 2017
Newborn babies experience the world through touch. Now, researchers who have measured the brain responses of 125 infants—including babies who were born prematurely and others who went full-term—show that a baby's earliest ...

Touch influences how infants learn language

April 23, 2014
(Medical Xpress)—Tickling a baby's toes may be cute but it's also possible that those touches could help babies learn the words in their language. Research from Purdue University shows that a caregiver's touch could help ...

Touching helps build the sexual brain

September 21, 2017
Hormones or sexual experience? Which of these is crucial for the onset of puberty? It seems that when rats are touched on their genitals, their brain changes and puberty accelerates. In a new study publishing September 21 ...

A mother's touch may help to bond with unborn babies

May 15, 2017
Babies may be able to recognise their mother's touch while still in the womb, helping them to bond even before birth, according to new research carried out at the University of Dundee.

Recommended for you

How the brain makes rapid, fine adjustments in motor activity

October 18, 2018
Short-term motor learning appears not to require physical change in the brain Brain's premotor cortex may use a 'neural scratch pad' to calculate fine adjustments Brain can try different things in simulation without 'screwing ...

Weight loss success linked with active self-control regions of the brain

October 18, 2018
New research suggests that higher-level brain functions have a major role in losing weight. In a study among 24 participants at a weight-loss clinic, those who achieved greatest success in terms of weight loss demonstrated ...

Scientists uncover how rare gene mutation affects brain development and memory

October 18, 2018
Researchers from the University of California, Irvine School of Medicine, have found that a rare gene mutation alters brain development in mice, impairing memory and disrupting the communication between nerve cells. They ...

Electrical properties of dendrites help explain our brain's unique computing power

October 18, 2018
Neurons in the human brain receive electrical signals from thousands of other cells, and long neural extensions called dendrites play a critical role in incorporating all of that information so the cells can respond appropriately.

Brain cells called astrocytes have unexpected role in brain 'plasticity'

October 18, 2018
When we're born, our brains have a great deal of flexibility. Having this flexibility to grow and change gives the immature brain the ability to adapt to new experiences and organize its interconnecting web of neural circuits. ...

Study pinpoints what makes human neurons unique

October 18, 2018
Human neurons are much larger than those of model organisms mice and rats, so it's been unclear whether it's size that makes a difference in our brain's computational power. Now, in a study appearing October 18 in the journal ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.