All learning and mental activity affects the brain in some way, to form memories and initiate responses to stimuli. That there could be visible changes that could be seen by inspection, through an X ray or a scan, was not accepted so far. When Sigmund Freud was a young doctor, the brains of the deceased, insane or schizophrenics were cut open to see if their condition was because of physical brain features. That no such features were found was a factor that spurred Freud to look elsewhere for therapy of persons with behaviour problems.

In the years since then, studies have shown that specific mental experience does bring about development of specific parts of the brain and modern methods of investigation have helped attain greater precision. A paper by Manuel Carrieras and others, in the journal Nature, reports that literacy acquired late in life is found to bring about visible changes in the brain anatomy.

Linguistic ability, of which sophisticated instances are seen even in children growing in intellectually less developed environments, is not even an exclusive human quality. Language is seen to develop in dolphins, birds, insects and is considered that certain basic grammar is inevitable in the communication processes.

But this is not true of reading and writing, exclusively human and develops only after years of training and practice. Whether this ability physically affects the brain, however, could not be studied, because literacy is usually developed early in life, in childhood, when there are many other experiential and developmental changes taking place.  

Tests on Colombian guerillas

Carreiras and colleagues found an opportunity to study the exclusive effect of literacy through the Columbian government’s programme to rehabilitate erstwhile guerillas, who have spent the first part of their lives fighting in the Columbian jungle. This population is of illiterate adults, with no formal education, now being put through training for reading and writing – and the structure of their brains can be compared with the brains of carefully matched persons who are yet to start learning.

Voxel based morphology 

The first studies were based on this method, which statistically analyses and maps the brain into small, 3 D cells called voxels. The word, voxel, is formed out of ‘volume’ and ‘pixel’ and represents a value on a regular 3 D grid, just like the pixel is an element of brightness on a 2 D grid drawn on the computer screen. In traditional size and volume studies of the brain, it was the dimensions of the whole brain or parts that were worked out. This was not only time consuming but also left out smaller differences. Voxel based morphology is a statistical method, where each cell represents a statistical average, irons out large anatomical differences and allows sensitive comparison of brain volumes at each voxel.

The first VBM studies that became well known were of the hippocampus region in the brains of London taxi drivers. The hippocampus is known to be associated with spatial skills, which taxi drivers in a busy city would need to possess. The study did show that the London cabbies had larger back part of the hippocampus than control subjects, an early instance of a mental ability related to physical difference in the brain.   

What MRI scans said...

The MRI scans taken of the brains of 42 right-handed, healthy adults – 20 of them the late-literate ex-guerillas and the remaining 22, a set of illiterates who had not started the programme, carefully matched in age and cultural background.

It was found that the ones who had become literate had markedly more grey matter, as opposed to white matter, in five areas of the brain known to get activated while reading. Grey matter is the brain component that contains neural cells and is responsible for information processing. White matter, in contrast, is the inter-neuron communication channel – passing information between areas of grey matter.

It was also found that the ability to read increases the white matter in the passage of communication between the two hemispheres of the brain. Damage to this area is often seen in cases of alexia, where a person has good language skills, but is simply not able to read. So, where there is no damage to this area, learning to read is found to increase its strength, with more white matter.

Similar brain structure differences were also seen in other persons, who were scanned and matched according to variations in cognitive ability. The same changes are also seen in children, upon gaining new skills. The conclusion is that the differences observed in the ex-guerillas are very likely the consequences of reading ability.

The group has carried out more experiments with different age and training groups to isolate structural differences in the brain, associated with specific learning experience. The group sees the late-literate subject, ie the Columbian guerillas, as an appropriate population with which more studies need to be done to minutely ‘tease apart’ specific components of literacy training led to differences in brain structure.