Putting Hemispheric Asymmetry to Use in Understanding Brain Diseases

Abstract

The time has come to use what we have learned over the past century and a half about hemispheric asymmetries to understand the bases of brain diseases. Left/right differences have been described for cognitive function, regional brain activation, neuronal connectivity, cortical thickness, structural volume, and neurotransmitter concentration in healthy individuals as well as for those with different forms of mental dysfunction. The missing element in research is to use these hemispheric differences to develop hypotheses to understand the underlying causes of the disorders. It is not enough, for example, to describe in schizophrenic patients language deficits which are attributable to the left hemisphere. Or suggest that impulsivity—a function controlled by the right hemisphere—is a problem for individuals with Attention Deficit Disorder or addiction. The question is whether there is anything about the neurobiology of the left and right hemispheres that we can use to give insight to the causes of these brain diseases. Today's technology to understand the brain at the cellular level can now be combined with what we know about cognitive behaviors to develop appropriate hypotheses.