Targeting regions of interest for the study of the illiterate brain

This paper reviews a work project that uses illiteracy as a tool to understand the way the brain adapts to information. The project follows the exploration of certain targets that can be identified with the functions of reading and writing, both from the functional and from the anatomical points of view. Results concerning visual processing, cross-modal operations (audiovisual and visuotactile), and interhemispheric crossing of information are reported. Studies with magnetoencephalography, with positron emission tomography, and with functional magnetic resonance provided evidence that the absence of school attendance at the usual age constitutes a handicap for the development of certain biological processes that serve behavioural functioning. Differences between groups of literate and illiterate subjects were found in several areas: while dealing with phonology a complex pattern of brain activation was only present in literate subjects; the corpus callosum in the segment where the parietal lobe fibres cross was thinner in the illiterate group; the parietal lobe processing of both hemispheres was different between groups; and the occipital lobe processed information more slowly in cases that learned to read as adults compared to those that learned at the usual age. Some behavioural studies suggest that there are other operations that can be explored from the image point of view.