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.
All Science Journal Classification (ASJC) codes
- Clinical Neurology