In the future, a nurse could determine whether a baby is likely to develop a reading disorder simply by attaching a few electrodes to its scalp and watching its brain waves respond to human speech. Such is the scenario suggested by a new study, which finds a potential biological indicator of how well preschool children perceive rhythm, an ability linked to language development.
“It’s really impressive to work with children this young, who are not often looked at,” says Aniruddh Patel, a cognitive neuroscientist at Tufts University in Medford, Massachusetts, who was not involved with the research.
Spoken language consists of sound waves occurring over multiple timescales. A syllable, for example, takes place over a quarter of a second, while a sentence unfolds over a few seconds. To make sense of this complex auditory information, humans use rhythmic cues such as stress and pause to discern words and syllables. Adults and school-aged children with reading disorders, however, struggle to pick up on these rhythmic patterns.
Scientists estimate that dyslexia and other reading disabilities plague about 5% to 10% of the population. Detecting such impairments early could lead to more effective intervention, but observing telltale signs in younger children who have not learned to read has proven a challenge.
So biologist Nina Kraus of Northwestern University in Evanston, Illinois, and her colleagues looked for automatic brain responses that can track language development in preschoolers, who have not learned to read. Researchers could measure such brain responses without requiring the kids to pay conscious attention to sounds, an advantage when it comes to working with young children. First, they asked 35 children between 3 and 4 years old to play a drum and synchronize their beats to that of a researcher’s, at speeds approximating the rate of stressed syllables in speech. Based on how well the kids kept time with the drumming, the researchers divided them into “synchronizers” and “nonsynchronizers.” The two groups did not differ in performances on intelligence and vocabulary tests.
Next, the team played syllable sounds like “ba” and “da” to the children and immediately recorded their brain waves responding to the sounds with electrodes pasted to their heads. The researchers also played a “da” sound mixed with background noise of babbling from six people to test how well the children can discriminate the syllables despite the noise. All the testing was done in one ear, while the children had the other ear free to listen to cartoons they brought—a measure designed to keep them engaged. The brain wave signals corresponding to the syllable sounds showed a clear pattern tracking the sound waves, which the researchers recorded down to the microsecond.
The results revealed that synchronizers’ brains processed syllable sounds with greater precision than nonsynchronizers, the team reports online today in the Proceedings of the National Academy of Sciences. In particular, they fared better at distinguishing syllables played in background noise. Within the synchronizers, those who followed the beat patterns more consistently also processed the syllable sounds more precisely.
The synchronizers performed better than nonsynchronizers on multiple tests of language abilities that pave the way for reading, such as identifying rhyming words. Four-year-old synchronizers performed more like 5-year-olds on these tests, while their nonsynchronizer counterparts performed more like 3-year-olds, Kraus says, and the synchronizers were better at discriminating melodies and rhythms in music.
Taken together, the results indicate that a preschooler’s ability to follow a beat predicts how advanced she is in developing language skills that support reading later on, Kraus says. Rhythmic ability also corresponds to how precisely a child’s brain processes speech syllables, she adds.
The research is only the beginning of a 5-year study that will track the same children across time to conclude whether neurological encoding of speech in children can indeed predict reading disorders, Kraus says. If the results bear out, future doctors may be able to assess whether newborns are at risk of developing reading disabilities even before the babies utter their first words, she says.
Detection this early could lead to intervention strategies such as music games to improve at-risk children’s rhythmic perception when their brains are most malleable, says neurologist Gottfried Schlaug of Harvard Medical School in Boston. “In general, earlier is better.”