Memory and forgetfulness have been viewed since antiquity from perspectives of physical, emotional, and spiritual states of well-being, and conceptualized philosophically. Numerous discussions of memory loss, or case reports, existed, but a fundamental advance in conceptualization of memory loss as a pathological clinical phenomenon originated when Sauvages classified "amnesia" as a medical disorder, in 1763. Originally, amnesia was recognized as a weakening or dissolution of memory, according to a taxonomy that ascribed known causes to the disorder. Etiologic factors included neurological disorders of stroke, hemorrhage, and head injury, metabolic dysregulation, alcohol and substance abuse, toxicity, anoxia, and other acute or chronic (sometimes progressive) brain disorders. Clinical descriptions of amnesia appeared internationally in medical dictionaries and scientific encyclopedias in the early 19th century. The possibility that amnesia could be either idiopathic, or symptomatic of another illness, was proposed based on the wide range of recognized etiologies and associations. Debate ensued regarding the status of amnesia as an illness or a symptom, but regardless, amnesia was soon recognized as an independent disorder of memory, distinguishable from disorders of global intellect, or of consciousness, or of language. Distinctions of amnesia considered its temporal gradient, duration and natural course, nature of onset, severity or depth of memory loss, course, and prognosis. Concepts of retrograde (forgetting knowledge preceding onset) and anterograde (difficulty learning, recalling new information) further specified the nature of amnestic memory difficulty. Alcoholic amnesia in Korsakoff's syndrome generated much attention. Amnesia as a clinical feature was critical to the development of notions of dissociation of conscious from subconscious recall in hysteria, and differentiation of neurogenically-based from psychogenically-based amnesia became central to understanding post-traumatic states. Amnesia studied as a disorder of memory remains an avenue to enrich clinical understanding of a condition that continues to be powerfully challenging to this day.
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