FUNCTIONAL NEUROIMAGES IN NEUROPHYSIOLOGY AND DEVELOPMENTAL NEUROPATHOLOGY

Key words: Neurophysiology, Developmental neuropathology, Myelinisation, Wernicke’s area, Gilles de la Tourette syndrome

he development of the cerebral cortex, mainly linked to gyration, especially in the prefrontal and visual areas, is the most distinctive phenomenon of the Homo species. From birth onwards, brain growth is mainly due to the numeric increase in the glia cells, whose ratio with the neurons goes from 1.7 at birth to 10 when the development is over, and to the growth and myelinisation of dendrites and axons (white substance). The maturation of each area occurs through an increase in the local ratio between white and grey substance. Numerous little differences distinguish male from female brain, being the male brain characterized by a major hemispheric asymmetry, minor diameter of the corpus callosum; major size of the amygdala, minor dimensions of the hippocampus; major dimension of the striatum and minor dimensions of the caudatum. At least some of these differences are due to the effect of testosterone, which is probably also responsible for the major incidence in males of a few disorders: hyperactivity (disorder of the right pre-frontal striated area, inhibiting system at the level of the base ganglions and cerebellum), dyslexia (Wernicke’s area) and autism (microstructural anomalies in rhomebencephalon, mesencephalon and in cerebellum, but also in the hemispheric cortex). Morpho-functional alterations can be observed in Gilles de la Tourette syndrome and in the compulsive obsessive disorder. Dorsolateral-frontal and prefrontal perfusion and metabolic defects, as well as an increase in the size of the hypophysis, can be observed in depression. A similar increase occurs also in nervous anorexia, accompanied by a (reversible) decrease in the cerebral substance thickness. Very small hyperdense focuses can be seen in the tension/tiredness syndrome.