In the course of human evolution, our ability to read is a relatively newly acquired trait. Hence, it is highly unlikely that a region of the brain could have evolved specifically for reading, unlike much more ancient functions like seeing or hearing. But, how is it that we are capable of this unique feat that involves recognising words and interpreting their meaning? Reading requires the coordinated functions of several regions in the brain, particularly associated with visual sensory processing.
In a recent study, an international team of researchers investigated the effects of reading on the visual system in the brain. The study was led by Dr Falk Huettig and Dr Alexis Hervais-Adelman from the Max Planck Institute for Psycholinguistics and included researchers from the Centre of Biomedical Research, Lucknow, University of Hyderabad, Hyderabad, University of Allahabad, Prayagraj, and Iswar Saran Degree College, Prayagraj. It was published in the journal Science Advances.
The researchers observed brain activity in about 90 subjects from two villages near Lucknow, Uttar Pradesh. They used a method called functional Magnetic Resonance Imaging (fMRI) to detect regions in the brain with high activity due to the increased blood flow. The chosen people had varying degrees of literacy and included those who could not read, as well as skilled readers. Those who were illiterate underwent a six-month program to learn reading Hindi in the Devanagari script.
After six months, the researchers showed these subjects various visual stimuli, like photographs of people, houses and also words, while scanning their brain activity. They found that a region in the ventral brain, called the visual word form area, becomes sensitive to processing words when one learns to read.
"The visual word form area (VWFA) is a particular focus of interest in reading research because it seems to be specialised for processing text," says Dr Hervais-Adelman in an interview with Research Matters.
The researchers hypothesise that since writing is relatively new to humans, there are no evolutionary adaptations specifically for it.
"Instead, the capacity to read must be based on other visual abilities in combination with linguistic abilities. The VWFA is believed to provide this capacity. It exists in a region of the brain that seems particularly adept at developing category-selective responses for stimuli that are relevant to our everyday lives," explains Dr Hervais-Adelman. This area is very close to an area of the cortex that is sensitive to faces.
Interestingly, the fMRI scans revealed that learning to read altered the response of several brain regions engaged during reading. The visual word form area showed a better response to letters and words. Previous studies had suggested that learning to read in adulthood had negative impacts on other regions in the brain, like the face-sensitive cortex. So, do these differences in the brain's response support that belief?
"Our study shows that it is not necessarily the case that gaining one visual skill will be bad for another", points out Dr Hervais-Adelman.
The study further looked at the similarities between the brain activity-patterns in the VWFA of all the subjects in response to text and non-text visual stimuli. Analysis of brain scans revealed considerable overlap in brain activity in response to words and other non-text stimuli. Moreover, representation of these various visual stimuli in the brains of skilled readers were found to be more similar than in less skilled readers. The researchers conclude that VWFA in skilled readers' brains retains a responsiveness to other stimuli, despite the emergence of sensitivity for text. Indeed, being able to read seems to go along with increases in overall response to other visual stimuli.
The study demonstrates that learning to read improves the overall visual brain responses and has a positive effect on our visual system. Perhaps there is more to what Joseph Addison said—"Reading is to the mind what exercise is to the body".
This article has been run past the researchers, whose work is covered, to ensure accuracy.