Effect of illiteracy on neuropsychological tests and glucose metabolism of brain in later life

Background and purpose: The acquisition of literacy during childhood may affect the functional organization of the brain. We studied the effects of illiteracy on neuropsychological tests and brain glucose metabolism in later life. Methods: We recruited 12 illiterate elderly farmers who never attended school and acquired no knowledge of reading or writing. These illiterate subjects were compared with literate subjects in terms of neuropsychological performance and brain glucose metabolism. All subjects were over 65 years and had same socioeconomic environment and normal activities of daily living. Results: Neuropsychological tests indicated that the performance of illiterate subjects was worse than that of literate subjects in all cognitive domains with the exception of forward digit span, tool-use and tool-free gestures, and verbal generation of grocery items. The SPM analysis showed that illiterate subjects had reduced FDG-uptake relative to literate subjects, predominantly in the rostral part of the left superior frontal gyrus and less strikingly in the left rectal gyrus, right cerebellar declive, and right cerebellar tonsil. In contrast, hypermetabolism was found only in the left precuneus. Conclusion: These results suggest that reading and writing during childhood is associated with activation of the frontal pole that may play a critical role in complex aspects of human cognition.