Interhemispheric communication in schizophrenia

Abstract

The corpus callosum (CC) is the brain's largest white matter tract, mostly composed by both myelinated and unmyelinated fibres, connecting the two cerebral hemispheres. The CC can be divided into different sections: rostrum, genu, body, isthmus and splenium (Aboitiz et al., 1992). Myelinated fibres predominate in the midbody and the splenium while unmyelinated fibres are more numerous in the rostrum and the genu. The callosal fiber disposition approximately reflects brain topography: the anterior sections connect the frontal lobes, the median sections connect temporal and parietal regions, and the posterior sections link occipital areas (Pandya et al., 1971). This traditional picture, however, which has been obtained mainly through studies in non-human primates has been partly modified by modern diffusion tensor imaging studies in humans (Hofer & Frahm, 2006). The CC matures after birth through adolescence and into early adulthood and is involved in different cognitive processes such as sensory-motor integration, attention, language, arousal and memory. Its size has been shown to be associated with handedness, sex (i.e., greater splenium in females and greater genu in males, Dubb et al., 2003) and cerebral laterality (i.e., inverse correlation between callosal connectivity and brain lateralization in males; Luders et al., 2003), and age (Ota et al., 2006) Specifically, age-related callosal degeneration has been detected by a diffusion tensor imaging (DTI) study (Ota et al., 2006) in the sub-regions that connect areas which are thought to be vulnerable to normal aging: the genu, rostral body, and isthmus. This result replicated post mortem findings of callosal degeneration in rostral body, anterior midbody and isthmus (Aboitiz et al., 1996).