Abstract
Brain lesion rarely produces a simple deficit of a certain mental faculty. It more often produces a pattern of cognitive and behavioral changes reflecting a complex combination of deficits (negative symptom) and apparently irrelevant extra activities (positive symptom) . Since the normal brain which is a super-complex neuronal structure performs its function by realizing a dynamic balance among relatively autonomous multiple functional systems, its damage not only results in hypo-activity of one functional system but also in hyper-activity of others. Many neuropsychological symptom complexes can be understood as manifestation of disturbance of such a dynamic equilibrium.
Four representative dynamic mechanisms underlying some of the neuropsychological symptoms were discussed based on the author's personal experience.
These are (1) disturbance of the balance between higher and lower nervous functions, (2) disturbance of the integration and rivalry between the left and right cerebral hemispheres, (3) disturbance of the integration and rivalry between the frontal and parietal functions, and (4) disturbance of integrative activity underlying linguistic capacity.
