Structural and functional reorganization of working memory system during the first decade in schizophrenia. A cross-sectional study.

INTRODUCTION: Progressive atrophy occurs in brain regions involved in the working memory network along the schizophrenia's course, but without parallel evolution of working memory impairment. We investigated the functional organization inside this network at different stages of the disease. METHODS: Twenty-eight patients with schizophrenia (16 with long disease duration (>60 months) and 12 with short disease duration (<60 months)) and eleven healthy controls underwent structural and functional MRI during an n-back task to determine atrophy and activation patterns. RESULTS: At similar n-back performances and relative to short disease duration patients, long disease duration patients activated more frontal temporal parietal and frontal network during 0-back and 1-back tasks respectively. n-back scores were correlated to atrophy in the frontal-temporal areas. DISCUSSION: Functional reorganization in the working memory network may play a compensatory role during the first ten years of schizophrenia.

Dyslexia: cultural diversity and biological unity.

The recognition of dyslexia as a neurodevelopmental disorder has been hampered by the belief that it is not a specific diagnostic entity because it has variable and culture-specific manifestations. In line with this belief, we found that Italian dyslexics, using a shallow orthography which facilitates reading, performed better on reading tasks than did English and French dyslexics. However, all dyslexics were equally impaired relative to their controls on reading and phonological tasks. Positron emission tomography scans during explicit and implicit reading showed the same reduced activity in a region of the left hemisphere in dyslexics from all three countries, with the maximum peak in the middle temporal gyrus and additional peaks in the inferior and superior temporal gyri and middle occipital gyrus. We conclude that there is a universal neurocognitive basis for dyslexia and that differences in reading performance among dyslexics of different countries are due to different orthographies.

Optic aphasia with pure alexia: a mild form of visual associative agnosia? A case study.

A single-case study is reported of a naming disorder selective to the visual modality. The patient showed intact access to structural knowledge of objects and letters, but impaired access to complete semantic knowledge of objects and alphabetical knowledge of letters from visual input. The impairment was most striking when the patient had to discriminate between semantically similar objects or within a given symbolic repertoire, i.e. letters. The co-occurrence of a partial deficit of visual recognition for objects and for letters indicated features of optic aphasia and pure alexia. This symmetric performance between object and letter processing may also constitute a mild form of visual associative agnosia.