[Subcortical dementia syndrome: semiology and physiopathology]

Among the dementia syndromes--that is, disorders of memory associated with a global alteration of cognitive functions sufficient to affect the subject's normal social behaviour--the current trend is to individualize a particular syndrome due to a primary dysfunction of the subcortical structures. The main characteristics of this syndrome are a slowing down of cognitive processes (bradyphrenia), a preferential disturbance of the fundamental processes (memory, motivation, attention, etc.) and a relative preservation of specific functions (speech, praxis, gnosis). Such a syndrome has been described not only in some cases of degeneration of the basal ganglia, but also in other brain diseases, notably vascular diseases, and in severe depressive states. Various recent clinical or fundamental studies have shed some light on the neuronal and neurochemical substrate of the syndrome, thus providing proof of the reality of the subcortical dementia concept which contributes to a better understanding of the relationship between brain and mental functions.