Verbal memory decline in Alzheimer's disease: a multiple-processes deficit.
Memory dysfunction is a primary diagnostic criterion and one of the earliest clinical manifestations of dementia of the Alzheimer type (DAT). The profile of progression of this memory deficit is assumed to represent a unitary decline. We studied the profile of verbal memory decline using an immediate free recall learning task in 18 DAT patients judged to be at 3 different stages of severity (mildly, moderately, and severely affected), using the serial-position function as the dependent measure. Results showed that the pattern of performance of DAT patients depended upon the severity of the disease. With mild dementia, the U-shaped curve was qualitatively similar to that observed in normals (presence of primacy and recency effects). With increasing severity of dementia, there was a consistent modification of the serial-position function with, in moderately affected subjects, a progression toward a unimodal curve devoid of a primacy effect and, later on, a decrease of the recency effect. These findings suggest that the serial-position function shows dynamic changes across stages of DAT. These dynamic changes may imply distinct disturbances of 2 or more learning-memory processes in this condition. The processes involved presumably reflect the temporal nature of the pathologic involvement of distinct neural systems, both structural and neurochemical.
Pepin
E P
EP
Neurology Service, University of Montreal, Hôtel-Dieu de Montréal, Canada.
Eslinger
P J
PJ
D000544:Alzheimer Disease / Q000523:psychology*; D006801:Humans; D008568:Memory / Q000502:physiology; D011939:Mental Recall / Q000502:physiology; D012720:Severity of Illness Index; D014706:Verbal Learning / Q000502:physiology