The two terms listed previously are used interchangeably to designate a unique and disorder of cognitive function in which memory and learning are greatly impaired almost in isolation from all other components of mentation and behavior. The amnesic state, as defined by Ribot, possesses two salient features that may vary in severity but are always conjoined: (1) an impaired ability to recall events and other information that had been firmly established before the onset of the illness (retrograde amnesia) and (2) an the inability to acquire new information, that is, to learn or to form new memories (anterograde amnesia). This duality inspired the White Queen, one of Lewis
Carroll’s characters, to quip, “It’s a poor sort of memory that works only backwards.” In other words, the functions of memory and learning are inseparable. A third feature of the Korsakoff syndrome, contingent upon retrograde amnesia, is impaired temporal localization of past experience. Other cognitive functions, particularly the capacity for concentration, spatial organization, and visual and verbal abstraction, which depend little or not at all on memory, are usually not affected. Equally important in the definition of the Korsakoff syndrome, or amnesic state (these terms are preferable to the older term, Korsakoff psychosis), is this integrity of certain aspects of behavior and mental function.
In order to establish the presence of the Korsakoff syndrome, the patient must be awake, attentive, and responsive—capable of perceiving and understanding the written and spoken word, of making appropriate deductions from given premises, and of solving such problems as can be included within his forward memory span. These features are of particular diagnostic importance because they help to distinguish the Korsakoff amnesic state from a number of other disorders in which the basic defect is not in memory but in some other abnormality—for example, impairment in attention and perception (as in the delirious, confused, or stuporous patient), in loss of personal identity (as in the hysterical patient), or in volition (as in the apathetic or abulic patient with frontal lobe disease or depression).
Immediate recall, a function of working memory, allows the patient with Korsakoff syndrome to repeat a string of digits, but this is more a measure of attention and registration. Remote memory is relatively less affected than recent memory (the Ribot rule, as discussed later).
The creative falsification of memory in an alert, responsive individual is often included in the definition of the Korsakoff amnesic state but is not a requisite for diagnosis. It can be provoked by questions as to the patient’s recent activities. The replies may be recognized as partially remembered events and personal experiences that are inaccurately localized in the past and related with no regard to their proper temporal sequence. Less frequent in Korsakoff syndrome, but more dramatic, is a spontaneous recital of personal experiences, many of which are fantasies. These two forms of confabulation have been referred to as “momentary” and “fantastic.” In the patients with the alcoholic Korsakoff syndrome studied by Victor and Agamanolis, fantastic confabulation was observed mainly in the initial phase of the illness, in which it could be related to a state of profound general confusion. In the chronic, stable stage of the illness, confabulation was rarely elicitable irrespective of how broadly this symptom was defined. Confabulation therefore is not an obligate feature of the Korsakoff syndrome.
Neuropsychology of Memory