title: Behavioral Syndrome in Dementia: Neuroimaging Insights.
abstract: Noncognitive symptoms contribute prominently to the morbidity of demeting illnesses. CT, MRI, SPECT, and PET are powerful tools used to examine cerbral structure and function and can be utilized to help advance understanding of brain-behavior relationships. Recently, investigators have used neurimaging techniques to study the relationship between structural or functional cerebral deficits and noncognitive symptoms such as depressed mood, delusions, hallucinations, and agitated or disinhibited behaviors that occur in patients with dementia. Although the methodology and subsequent results of studies have varied, three tentative conclusions emerge: (1) Disinhibited and inappropriate social behaviors are most prominent among patients with neuorimaging evidence of frontal cortical dysfunction, across diagnostic categories of dementia syndromes; (2) Depressed mood, apathy, and blunted affect are associated with structural lesions in subcortical nuclei. Frontal cortical dysfunction may be crucial to the development of mood symptoms that result from subcortical lesions; (3) Delusions are associated with dysgunction of paralimbic or heteromodal association areas in the frontal or temporal cortex in patients wtih dementia. The collective neuroimaging evidence suggests that psychiatric and behavioral symptoms in dementia are not random consequences of diffuse brain illness, but are fundamental expressions of regional cerebral pathology. Further development of neuroimaging techniques, more focused neurimaging study designs, and corroboration with neuropathologic studies will help to clarify the pathophysiologic mechanisms involved in neuropsychiatric symptoms and will suggest opportunities for therapeutic intervention.