Psychogenic amnesia.

Time- and content-based memory systems are briefly described so that their importance for a refined analysis of memory disturbances becomes evident. These memory systems are then related to their brain instantiation, emphasizing that there are limbic circuits for encoding different forms of memories, largely cortical networks for memory storage, and a combined temporofrontal network acting to trigger information retrieval. The terms functional amnesias and psychogenic amnesias are discussed and their symptomatology is compared to that of organic amnesias. The term "mnestic block syndrome" is introduced and defined as a syndrome of its own. Experimental data, obtained especially with functional imaging methods, are presented to elucidate changes in neural activation during functional amnesic states. It is concluded that functional amnesic states, confined to a patient's biography, can be triggered by environmentally induced stress and trauma, leading to lasting inability to retrieve autobiographical events. Such an impairment may be identified at the brain level using functional imaging techniques.