Uniting Kraepelin and Bleuler: the psychology of schizophrenia and the biology of temporal lobe abnormalities.

Bleuler and Kraepelin are described as icons of the aggressively psychological and aggressively biologic approaches to schizophrenia. We suggest that methodologic advances in studying the function and structure of the brain now allow a reconciliation of these seemingly dissimilar approaches, particularly in the temporal lobe. We begin with a brief historic overview of these different approaches to schizophrenia and then describe structural (magnetic resonance imaging [MRI]), functional (event-related potential [ERP]), and neuropsychological studies in this disorder, including a summary of work conducted in our own laboratory. Recent MRI investigations agree on the presence of volume reductions in schizophrenia in the medial temporal lobe structures of the hippocampus-amygdala complex and of the para-hippocampal gyrus. Furthermore, two recent studies also indicate volume reductions in the superior temporal gyrus (STG). These volume reductions are most prominent in male patients and in the left hemisphere of right-handed patients with schizophrenia. Along with structural studies, there has been a burgeoning interest in MRI-clinical correlations, with volume reductions in the anterior STG being associated with hallucinations and those in the posterior STG being associated with thought disorder. Functional ERP studies also implicate the importance of the temporal lobe in schizophrenia; in addition, ERP abnormalities have been directly associated with a left greater than right MRI volume reduction of the posterior STG. Neuropsychological studies in nonpsychiatric patients are also consistent with a pattern of functional deficits shown to arise from temporal lobe abnormalities, whereas direct MRI-neuropsychological correlations in schizophrenic patients show that decreased performance on tests of verbal memory, abstraction, and categorization correlates with reduced MRI volume of left and right temporal lobe structures. Integration of these findings with those from basic neuroscience suggests a possible role of excitatory amino acid neurotransmission dysregulation and excitotoxicity in the pathology of schizophrenia. A data-based pathophysiologic characterization of schizophrenia is now becoming a reality, and the next few years should see a further unification of the Kraepelinian and Bleulerian approaches to this disorder.