Former guerrillas in Colombia have helped neuroscientists locate which parts of the brain are involved in literacy, according to a study published on Wednesday in the British journal Nature.
Language is an innate human ability that evolved after chimpanzees and hominids split from a common ancestral path around six million years ago.
Reading, though, is a learnt skill, acquired through intensive education and practice.
But which regions of the brain are harnessed to help us read — and how the brain changes as we acquire literacy — have until now been poorly understood.
One of the challenges has been to find appropriate sources for study.
Most people learn to read as children, when they are also learning social skills and other activities. It can be almost impossible to discern which of these learning influences can be traced specifically to reading as opposed, say, to learning a sport.
Studying adults also poses a problem, because in most advanced economies illiterate adults have typically suffered ill health or learning impairments. These too are potential “confounding factors” that can skew data.
Researchers from Spain, Colombia and Britain seized a golden chance to find out more, thanks to 20 former rebels in Colombia who took part in an adult literacy course to help them reintegrate society.
After the volunteers had become literate, magnetic resonance imaging (MRI) scans of their brains were compared with those from 22 illiterates who were matched for age and cultural background.
The new readers had a higher density of so-called grey matter, where information processing is carried out, in several areas of the left hemisphere of the brain, the investigators found.
Previous research has already determined that these areas are responsible for recognising the shapes of letters and translating the letters into speech sounds and deriving a meaning from them.
Reading also boosted neural connections, known as white matter, between the different regions of grey matter.
The team took the findings a step further by looking at the brains of people who mastered reading in childhood.
The big discovery is the role of part of the brain called the angular gyrus.
For almost a century and a half, the angular gyrus has been thought to recognise the shapes of visual words and then translate them into sounds and meanings.
But, according to the new paper, the angular gyrus plays an intermediary part, providing predictions of what the brain will see.
“The traditional view has been that the angular gyrus acts as a ‘dictionary’ that translates the letters of a word into a meaning,” said Cathy Price, a professor at University College London, in a press release.
“In fact, we have shown that its role is more in anticipating what our eye will see — more akin to the predictive texting function on a mobile phone.”
The investigation could unlock understanding into the causes of dyslexia, the researchers hope.
