Contributions of neuropathology to understanding schizophrenia in late life.

The neurobiological basis of cognitive and functional deterioration commonly observed in elderly persons with schizophrenia is unclear. Despite superficial similarities in the clinical and neuropsychological profiles of schizophrenia in late life with neurodegenerative dementias, extensive neuropathological investigations have failed to find any evidence of neurodegeneration or neural injury beyond what is typically observed in brains of individuals without neuropsychiatric illness. In contrast, growing neuropathological data indicate aberrant brain development and connectivity in schizophrenia (including abnormalities in cytoarchitecture, innervation, and synaptic integrity) and abnormal molecular signaling pathways important in the formation of the nervous system and ongoing plasticity in maturity. These developmental abnormalities may represent a state of decreased cerebral reserve that causes persons with schizophrenia to be more vulnerable to the toxic effects of even "normal" accumulations of age-related neurodegenerative lesions.