Brain Organization Volume 6, Number 6, 2000THE NEUROSCIENTIST REVIEW n Neurobiological Substrates of Illiteracy ALEXANDRE CASTRO-CALDAS and ALEXANDRA REIS Lisbon Center for Neurosciences Lisbon, Portugal Comparable subjects except for the knowledge of orthography and school attendance in the proper age provided the case material for a series of studies that are reviewed. The results suggest that the acquisition of orthographic skills provides a basis for changes in the pattern of activation of the brain. NEUROSCIENTIST 6(6):475–482, 2000 KEY WORDS Illiteracy, Language, Reading, Writing, Learning, Brain organization The brain can be understood as an organ that adapts to several types of internal and external influences. The in- teraction of these complex concurrent stimuli along life shapes the highly differentiated biologic arrangement of the brain and its consequent physiology, at any given time. The past years have seen a significant development of the knowledge about the neural substrate of language in its oral and written forms. This is, in part, the result of understanding acquired oral and written language disor- ders (see, for example, the reviews of Neville and Bavelier [1], Patterson and Ralph [2], and Price [3]), of studies on the influence of sensory deprivation on the harmony of the so-called normal development (4), and of functional brain scanning of normal subjects while they perform tasks related to these skills (5, 6). This brief review is based on the assumption that the neurobiology of oral and written language is generally understood as the result of the interaction of the follow- ing structures and mechanisms: 1. auditory cortex and cortical and subcortical motor mechanisms responsible for modulating phonology; 2. auditory cortex and multisensory integrative cor- tex responsible for the lexicon-semantic components; 3. visual cortex, and its connections to mechanisms 1 and 2, responsible for reading; 4. parietal cortex and the dorsal visual connection responsible for visually guided movement that is the origin of writing; and 5. connections among all of these mechanisms. Learning to Read There is considerable evidence that the mastering of the written component of language entails the action of many more areas of the brain than those simply respon- sible for the mechanisms of oral production (as repre- sented in the cartoon in Fig. 1). Learning orthography can be considered as involving the adding at least of a visuo-spatial component to a previous existing au- dio-temporal mechanism. The adaptation to the new type of information con- cerns not only the recruitment of new mechanisms and therefore new regions of the brain but also a change in the proper oral-language-supporting mechanism. In the case of reading, bringing the implicit processing of pho- nology to a declarative conscious level is the main change of this acquisition (7, 8) because awareness of segmentation of word components is crucial for letter- by-letter reading (2). In his pioneer work, Morais et al. (9) demonstrated that illiterate subjects failed in performing a number of tasks that require phonological awareness. This biofunctional model can thus predict the changes that are introduced in the system following the formal learning of orthography at school. The Illiterate Population In certain regions of the world, as was the case in Portu- gal in the past, illiteracy due to social reasons is a com- mon finding. Indeed some 40 years ago, the first-born girl in a family was kept at home at the age of 6 instead of going to school. She was charged with being a care- taker for the other siblings, generally in large families. On the other hand, younger children, when reaching the age of 6 or 7, were sent to school because they were considered a nuisance for the normal functioning of the house. They spent all day at school and were fed there, which represented an economy for the meager budget of the family. We have studied a community that includes a significant number of illiterate people. In this commu- nity, mobility to other parts of the country is not com- mon because the main source of economy derives from the sea and life revolves around fishing activities. Thirty percent of the population older than 55 is totally illiter- ate in Portugal due to socioeconomic reasons. This fig- ure is higher in small rural or fishing communities such as the one where most of the subjects were selected. This is a small town, now composed of old and new THE NEUROSCIENTIST 475 Volume 6, Number 6, 2000 Copyright © 2000 Sage Publications, Inc. ISSN 1073-8584 Address correspondence to: Alexandre Castro-Caldas, University Department of Neurology, Hospital de Santa Maria, 1649-035 Lisboa Portugal (e-mail: ccneurol@esoterica.pt).