Callosal morphology in schizophrenia : what can shape tell us about function and illness ? {

The corpus callosum (Latin: ‘tough body’) is the human brain’s largest white matter tract, and its largest commissure. The callosum was first named by Galen of Pergamum in ancient Rome, at the beginning of the first century AD, among a range of other central nervous system structures. Up until the 16th century, it was generally felt to be a supporting or ‘scaffolding’ structure only. In 1543, Andreas Vesalius described its anatomy for the first time, recognising that it linked the two halves of the brain and was continuous with the white matter of the hemispheres. In the 1600s, La Peyronie, Professor of Surgery at Montpellier, selected it as the ‘seat of the soul’, as it seemed to be the most interconnected of brain structures. Our modern view of the corpus callosum recognises its crucial role in connecting the cerebral hemispheres. The callosum forms a high-bandwidth neural pathway between the two hemispheres, facilitating information transfer and unifying information that enters in a lateralised fashion into the hemispheric system. It contains in the region of 60 million axons, fibres that mediate sensory–motor coordination, and connect equivalent association cortical regions across hemispheres. The callosum has a critical role in attentional arousal, and the integration and communication of high-level motor, cognitive and sensory information. Given that fibres from most cortical regions traverse the callosum, it is seen as an attractive structure to study as regional brain changes can be reflected in regional shape changes in the callosum.