Imperial College London scientists have created the world’s first non-invasive way to map how baby movements are generated on a neuronal level.
The research, carried out using a wearable cuff, provides a new method for monitoring movements in babies, and new insights into how babies’ reflexes – like kicking – develop. These insights and the cuff could also be used to spot early signs of motor disorders such as cerebral palsy.
This is a fundamental discovery of how foetuses and babies develop.
Professor Dario Farina, Department of Bioengineering
Babies start kicking as foetuses in the womb and continue to kick instinctively until they are around four months old. The kicks mainly involve spinal neurons, as do protective reflexes found in adults like swiftly removing a hand from heat. However, not much is known about how the movement is generated on a neuronal level because detailed analysis of individual nerve cells has previously not been possible without surgery.
Now, Imperial and Santa Lucia Foundation researchers have developed a non-invasive cuff that slips onto freely kicking babies’ legs to monitor neuronal activity without the need for surgery. The system decodes the electrical field potentials on the body surface and mathematically reverses their generation process, thus identifying the neural activity of the spinal cord.
|Fig.1. Spinal cord neurons, how the cuff attaches to the baby, and the synchronisation of neurons during kicking. Del Vecchio A, Sylos-Labini F. et al.|
Using the cuff the researchers found that, unlike fast leg movements in adults, babies’ kicks are generated by the neurons in the spinal cord firing at the exact same time. This ‘extreme synchronisation’, the researchers say, increases the force generated by muscles attached to the nerves – which explains why babies’ kicks can be relatively hard and fast even though their muscles are still weak and slow.
This is an exciting achievement that could help us monitor babies for signs of motor problems so that we can diagnose and treat them early. Professor Francesco Lacquaniti, Santa Lucia Foundation
The researchers say these results, which are published today in Science Advances, are crucially important for our understanding of the development of spinal neural networks.
Lead author Professor Dario Farina of Imperial’s Department of Bioengineering said: “This is a fundamental discovery of how foetuses and babies develop. The findings, and the new technology that helped us make the discovery, could help monitor development in babies and spot signs of motor disorders like cerebral palsy early on.”
Co-senior author Professor Francesco Lacquaniti of the University of Rome Tor Vergata and Santa Lucia Foundation added: “The new monitoring cuff is an exciting technological achievement that could help us monitor babies for signs of motor problems so that we can diagnose and treat them early.”
The cuff attaches to the lower leg and contains a neuromuscular interface which records the electrical signals on the skin. It then decodes these signals and their timings to work out which spinal cord neurons are firing, and how quickly.
They tested the cuff on four freely kicking healthy babies aged two to 14 days old, and on twelve adult men doing various movements.
They found that in babies, all neurons fire closely in time to generate a kick, whereas there was significantly less synchronisation in the adult individuals.
|Fig. 2 High-density EMG activity and motor unit discharge times in neonates. (A) Two grids of 64 electrodes (128 electrodes in total) covered most of the anterior lower leg of the neonates. The EMG grids were aligned with the direction of the tibia bone. The interelectrode distance was 4 mm. Photo credit: Alessandro Del Vecchio, Imperial College London. (B) Ten EMG channels showing common myoelectric activity during spontaneous movements. Vertical red lines indicate the time intervals when the RMS values were computed for each EMG channel. RMS was projected in 2D maps. (C) Four interpolated EMG-amplitude maps. The time windows correspond to the red lines in (B). These maps show distinct patterns of activation, resulting from activation of different muscles or distinct motor unit innervation zones. We then applied blind source separation on the EMG signals and identified the constituent motor unit action potentials. (D) Average EMG activity across all 128 channels with a 2-Hz low-pass filter (redline). (E) Raster plot of the discharges of six identified motor units. (F) The instantaneous discharge rate of these neurons displayed in a 10-s interval. Del Vecchio A, Sylos-Labini F. et al.|
Professor Farina said: “Generating fast movements is vital for human survival and health. Babies can already kick very fast just days after birth, and now we know that they do so using all spinal nerves at the same time.”
Baby kicks are thought to strengthen leg muscles and prepare the infant to roll over and eventually learn to walk. However, the researchers say their findings could suggest another advantage.
Perhaps babies developed such strong kicks through evolution to avoid potential dangers like predators. Dr Alessandro Del Vecchio, Department of Bioengineering
First author Dr Alessandro Del Vecchio from Professor Farina’s research group in the Department of Bioengineering said: “The strength and speed of the kicking, as well as the synchronisation of nerve activity, could suggest that kicking has a more immediate protective advantage for babies. Perhaps babies developed such strong kicks through evolution to avoid potential dangers like predators.”
The researchers are now looking into monitoring spinal neurons in babies with motor disorders like cerebral palsy. They hope their research could help to develop new clinical markers for the early diagnoses of these types of disorders.
|This work was funded by the European Research Council.|
Spinal motoneurons of the human newborn are highly synchronized during leg movements, Del Vecchio A, Sylos-Labini F, Mondì V, Paolillo P, Ivanenko Y, Lacquaniti F, Farina D. Sci Adv. 2020 Nov 20;6(47):eabc3916. doi: 10.1126/sciadv.abc3916. Full text
Functional imaging of the developing brain with wearable high-density diffuse optical tomography: A new benchmark for infant neuroimaging outside the scanner environment, Frijia EM, Billing A, Lloyd-Fox S, Vidal Rosas E, Collins-Jones L, Crespo-Llado MM, Amadó MP, Austin T, Edwards A, Dunne L, Smith G, Nixon-Hill R, Powell S, Everdell NL, Cooper RJ. Neuroimage. 2020 Oct 24:117490. doi: 10.1016/j.neuroimage.2020.117490. Epub ahead of print.
Wearable imaging cap provides a window into babies’ brains University College London