Scientists have long wondered when the sense of rhythm first takes shape in the developing brain.
It’s been a difficult question to answer not least because studying this in foetuses is almost impossible. But when instead scientists turned to premature newborns, whose brains are at roughly the same stage as foetuses in the final weeks of gestation, they found a surprise.
According to a new study in iScience, when these preterm infants hear rhythmic sounds, their brains light up not only in areas that process hearing but also in regions involved in movement — hinting that the connection between sound and motion begins earlier than anyone had confirmed before.
“Auditory rhythm processing begins very early in development,” the study’s corresponding author Sahar Moghimi, a researcher at the University of Picardy Jules Verne in France, said. “Even before the third trimester, the auditory system becomes functional and starts encoding external sounds.”
The results suggest that the sense of beat, long thought to emerge after birth, may already be shaping early connections between song and dance.
Beats before birth
The researchers used a noninvasive imaging method called functional near-infrared spectroscopy (fNIRS) to record brain activity in premature infants while they slept. The babies were around 36 weeks of gestational age — still several weeks from their due date while already undergoing rapid brain development.
They were exposed to sequences of rhythmic and irregular sounds. The rhythmic patterns produced a steady beat while the irregular ones didn’t induce a predictable pulse. The team confirmed that rhythmic sounds activated not only the brain’s hearing area but also those areas that plan and control movement. The irregular patterns produced weaker, more limited activity, suggesting the developing brain could already organise sounds into regular patterns in time, as if anticipating a beat.
“The brain is already responding to rhythm, much before birth — the same ability that later helps shape language and social communication,” Dr. Moghimi said.
Rhythmic sounds also activated more of the brain than expected. The areas that plan and control movement responded more strongly to regular beats, suggesting the brain had also started linking sound and movement internally and was preparing for the synchrony that researchers know emerges only months later.
Even without the beats, the foetus in a womb is already immersed in rhythm — from the steady pulse of the mother’s heartbeat to the cadence of her voice. The study’s authors reasoned that this exposure may be helping wire the foetus’s auditory system to detect a steady beat and build the brain’s sense of timing.
“Exposure to auditory rhythms may be important for the development of other brain regions beyond hearing areas,” Dr. Moghimi said.
Although a preterm infant’s motor cortex is still immature, its early responsiveness to rhythm suggests that links between hearing and movement begin forming early, laying the groundwork for later milestones in perception and coordination.
An early partnership
“The observation is truly exciting,” said Simone Dalla Bella, who studies audition and motor abilities at the University of Montreal in Canada.
He said research has already shown that newborns only weeks old can detect complex rhythmic patterns and that infants a few months later are able to sense the differences between beats such as a march or a waltz when gently moved to music.
What makes the new study distinctive, he continued, is that it captures this coordination before birth, when the motor system is only beginning to mature.
“This study confirms that rhythm plays a critical role very early in life,” Dr. Dalla Bella said. “It suggests that the brain’s ability to pick out steady patterns in sound and link them to movement may be at least partly hard-wired.”
He added that the work reinforces a key idea in rhythm research: that the motor system isn’t just something that moves after we learn to hear but an active partner in shaping perception from the ‘very beginning’.
While Dr. Dalla Bella also highlighted how early rhythm coordination could shape development, other researchers are asking what enables such synchronisation inside the brain.
Edward Large, who studies auditory neuroscience at the University of Connecticut in the USA, said the findings strengthen evidence that the brain’s rhythm circuits are active long before voluntary movement appears.
“Auditory responses alone cannot explain the brain activity seen here,” he said.
However, Dr. Large also said the imaging method used in the study, fNIRS, is too slow to track the rapid brain waves that underlie rhythm perception. The scans showed that motor regions are active but they can’t reveal whether those responses are themselves rhythmic.
“We may guess, based on earlier EEG studies, that they are,” he said.
Even so, he added, the results fit with a growing view that rhythm perception arises from self-organising neural oscillations linking hearing and movement areas — a kind of built-in resonance that may help the brain learn and coordinate from its earliest stages.
The brain’s first music
For neonatologists, the finding that rhythmic sound engages motor regions even before term offers a window into how early brain connections form.
“Rhythmic sounds may help stimulate both hearing and motor regions, supporting early synaptic growth in the developing brain,” Surendra Singh Bisht, who heads paediatrics and neonatology at the Swami Dayanand Hospital, New Delhi, said.
Dr. Bisht explained that in foetuses and newborns, smooth, symmetrical general movements — the spontaneous motions newborns make — are among the most reliable signs of healthy brain connections.
“These general movements are closely linked to how well brain cells connect and communicate,” he said.
Infants with smoother movements tend to have better neural coordination and are less likely to develop cerebral palsy later in life.
“It’s a direct clinical clue to how the brain’s motor networks are wiring themselves,” Dr. Bisht said.
To be sure, the findings don’t mean preterm infants can recognise a tune or pulse, only that their brains are already preparing to do so. Long before babies sway to a lullaby or match their mother’s speech rhythms, their brains appear to be linking sound and movement in preparation for both.
To Dr. Moghimi, this early sensitivity underlines rhythm’s role as a foundation for learning.
“The presence of elaborated neural capacities for processing rhythm so early in life highlights its importance as a building block for learning from regularities in the world,” she said.
In that sense, rhythm may be the brain’s first music — an internal pattern that helps the mind make sense of the world before life has even begun.
Anirban Mukhopadhyay is a geneticist by training and science communicator from New Delhi.
