Sunday, 12 December 2010

Retrograde Amnesia (Ency. Britannica)

Retrograde amnesia

Open Workspace Since retrograde amnesia relates to memory for events that took place when brain function was unimpaired, it clearly cannot be ascribed to failure of registration—with the exception, perhaps, of the very brief permanent amnesias following electroconvulsive shock or head injury. Retrograde amnesia otherwise would appear to be wholly due to a failure of retrieval, though this failure is evidently selective. That recent memories are generally harder to evoke than those more remote is usually explained on the basis of consolidation; i.e., progressive strengthening of memory traces with the passage of time. Yet, recency is not the only factor, and in some cases memory for a relatively recent event may still be preserved while that for one more remote is inaccessible. Much depends, too, on the method used to test retrieval; e.g., recognition may succeed when voluntary recall entirely fails. By and large, the availability of information in memory would seem to depend to a considerable extent on its relation to the person's current interests and preoccupations. When these are severely curtailed by an amnesic state, the links connecting present and past are severed, with a consequent failure of reproduction.

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