Relevance of the serial position effect in the differential diagnosis of mild cognitive impairment, Alzheimer-type dementia, and normal ageing

Abstract

Serial position effects are observed when a person memorises a series of words exceeding his or her attention span. Cognitively normal individuals recall words at the beginning and end of the list more frequently than those in the middle, which reflects the way that short- and long-term episodic memory works. ObjectiveTo study the serial position effect in patients with mild cognitive impairment (MCI) compared to subjects with Alzheimer-type dementia (AD) or normal ageing (NA). Methods30 AD, 25 MCI and 20 NA subjects underwent neurological and neuropsychological assessment. The Rey Auditory Verbal Learning Test (RAVLT) was used to study primacy, middle, and recency effects and delayed recall for each group. ResultsThe general memory pattern of MCI subjects was very similar to that of AD subjects, and was characterised by reduced learning capacity, rapid forgetfulness and clear recency effect in learning. With regard to delayed recall, however, there were differences in performance; MCI subjects’ ability to recall words at the beginning and middle of the list was similar to that of normal subjects, while their memory of words at the end of the list was poor, as in AD subjects. ConclusionsRAVLT is a tool permitting us to distinguish between MCI and NA subjects. The recency index for the delayed recall task is a valid indicator for distinguishing between MCI patients and patients with normal ageing.