THE FRAGILITY OF REMEMBERING – DATA FROM CLINICAL CASES

Abstract

"False memories, memory distortions, confabulations, and other forms of memory aberrations and deficits occur in everyday life and – more frequently – in neurological and psychiatric patients. We studied such changes of memories in 42 patients with alcoholic Korsakoff’s syndrome, 18 with clipped or ruptured aneurysms of the anterior communicating artery [ACoA], 41 with a diagnosis of dissociative amnesia, and 52 healthy control individuals. All three patient groups had severe memory deficits. The neurological patients had deficits both with respect to acquiring new semantic and episodic memories, while the psychiatric patients were unable to retrieve episodic memories only. Both the neurological and the psychiatric patients had major problems in retrieving old episodic memories. However, the groups differed in that way, that the neurological patients tried to compensate their deficits by showing numerous confabulations (especially patients from the Korsakoff’s group), while the group with ruptures and repairs of their ACoAs showed a considerably tendency towards producing false memories. The psychiatric patients, on the hand, demonstrated a total lack of retrieving episodic memories from their past and showed no efforts to invent or generate alternative memories. It is concluded that especially the prefrontal cortex (frontal lobes) and its associated structures (mediodorsal thalamus, which is regularly degenerated in patients with Korsakoff’s syndrome) are relevant in controlling proper and accurate retrieval of information. This statement also seems to be confirmed from functional imaging results in patients with dissociative amnesia who show a reduced prefrontal metabolism. For normal individuals, states which reduce alertness (e.g., fatigue, sleep deprivation) and consequently dampen prefrontal control functions, similarly can lead to a heightened degree of fragile memory retrieval."