A specially adapted medical scanner for infants has revealed for the first time how brain wiring develops in the first few months of life.
Magnetic resonance imaging (MRI) has become a vital part of medical research and diagnosis in adults, but it is technically difficult to perform in children and infants. Subjects must be completely still and it can be an intimidating, noisy and claustrophobic experience even for adults.
Dr Sean Deoni, lead researcher of the project at King’s College London, explained how they overcame these hurdles.
‘The babies come in with their families around an hour before we hope to scan and we put them into a private room where they can relax. When the baby finally falls asleep after feeding we gently move them in to the scanning room.
‘In terms of the scanner itself we’ve put a soundproofing insulator inside the bore, this allows us to absorb some sound giving a couple of decibels reduction and we use some special noise attenuating headphones that go around their ears.’
But the crucial modification was slowing down the actual process of acquiring the image, because the faster the data capture the louder the scanner is. This allowed them to get noise levels down to around 60 decibels, equivalent to a normal human conversation, which infants can easily sleep through. The down-side is that scan time goes up dramatically by a factor of two, but Deoni said this can be offset by being more selective about what data to capture.
With the technique established, the team set to work on a biological question – how nerves develop their insulating layer of myelin, which makes transmission of signals quicker.
‘Myelinated white matter is really just the highways of your brain, and as you myelinate you basically go from a single lane road, to a dual carriageway, up to an interstate, so just getting faster and more efficient.
‘The other thing that happens is your metabolic need drops dramatically, so it doesn’t take as much energy to send a pulse between two brain areas – if we didn’t have myelinated white matter our brain would have to be about five times as big.
Scanning 14 healthy babies between the ages of three and 11 months the researchers found that by nine months myelination was visible in all brain areas and in some regions had developed to a near-adult level. This suggests that abnormalities in myelination may have profound consequences in terms of disability and mental disorders.
Indeed, multiple sclerosis is caused by a localised loss of myelin leading to vision, speech and motor problems.
Deoni now plans to conduct follow-up studies, one potentially interesting area being autism.
‘Even though you can’t definitively diagnose it until about two or three years of age, parents of autistic children generally notice that something is…not quite right at about six, seven or eight months of age and that’s really when a lot of areas [of the brain] are beginning to myelinate.’