Theodor Meynert: foreshadowing modern concepts of neuropsychiatric pathophysiology.

Theodor Meynert's neuroanatomic studies contributed to the development of the nineteenth-century "brain psychiatry" movement. His speculations--that certain cognitive impairments resulted from an imbalance in blood flow between cortical and subcortical structures--parallel modern controversies concerning the role of these brain regions in the pathophysiology of dementia. Meynert described a subcortical nucleus in the basal forebrain, the nucleus basalis of Meynert, which has recently been shown to provide cholinergic innervation to the cortex. Loss of cells in this structure in Alzheimer's disease, a so-called "cortical" dementia, and in the dementia of Parkinson's disease, a so-called "subcortical" dementia, probably accounts for the loss of cortical cholinergic markers in these diseases. An understanding of Meynert's contributions may avoid unproductive speculation in attempts to study the interactions between cortical and subcortical structures in neuropsychiatric diseases.