Short-term memory impairments in Alzheimer-type dementia: evidence for separable impairments of articulatory rehearsal and long-term memory.
Two experiments are described which investigate the short-term memory deficits found in Alzheimer-type dementia. In the first experiment memory span for words of differing spoken duration is related to speech rate. Memory span was lower in subjects suffering from Alzheimer-type dementia than for normal elderly controls but in both cases a linear function related recall to speech rate for items of differing spoken durations. The function for Alzheimer subjects had an equivalent slope (interpreted as reflecting a contribution from a sub-vocal rehearsal process) but a lower intercept (interpreted as reflecting a contribution from a long-term memory component). The second experiment investigated the effects of repeating supra-span lists of items in a serial recall task. As predicted the control subjects showed substantial increases in recall across trials associated with elevations of the speech rate/recall functions while the Alzheimer subjects showed very little benefit from repetition of the lists. We conclude that the verbal short-term memory deficit found in Alzheimer-type dementia has two components: a deficit in the rate of rehearsal and an impairment in the long-term memory component of short-term recall.
Hulme
C
C
Department of Psychology, University of York, U.K.
Lee
G
G
Brown
G D
GD
D000368:Aged; D000544:Alzheimer Disease / Q000523:psychology*; D003071:Cognition / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008569:Memory Disorders / Q000523:psychology*; D008570:Memory, Short-Term / Q000502:physiology*; D012691:Serial Learning / Q000502:physiology; D013060:Speech / Q000502:physiology*