Individual Differences in the Anatomy of the Corpus Callosum: Sex, Hand Preference, Schizophrenia and Hemisphere Specialization

Recent studies of the gross anatomy of the corpus callosum show that there is marked variation in its size and shape, but also considerable consistency in these variations across very diverse studies. One study to date has reported a larger callosum, particularly in the mid and anterior regions, in mixed and left handers compared to consistent right banders. Several reports have examined possible sex differences in callosal anatomy and have produced apparently inconsistent results. The evidence clearly does not support a larger posterior splenial region in absolute size in females. However, a minority of the studies suggest that the posterior region, proportional to the size of the total callosum, may be larger in females than in males. Further clarification is needed. The early studies of callosal anatomy in schizophrenia suggested a thicker callosum in schizophrenics. Subsequent studies do not support this finding and may be confounded by variables such as chronological age, body size, brain size, and type of control group. Any anatomical differences between schizophrenic and normal individuals may involve some interaction of callosal region, sex and hand preference. These results are discussed in relation to individual differences in hemisphere specialization and brain function.