Frontal dysfunction and memory deficits in the alcoholic Korsakoff syndrome and Alzheimer-type dementia

This study investigated the intercorrelation of 8 'frontal' tests in 32 patients with Korsakoff's syndrome and Alzheimer's disease, and examined the relationship of frontal dysfunction to impaired release from proactive interference and impoverished retrieval from retrograde memory. Amongst the frontal tests, there were statistically significant intercorrelations between 3 'fluency' tests and 3 'card-sorting' tests, although the degree of shared variance was relatively low. The relationship of another test--picture arrangement errors--was more equivocal; performance for 'cognitive estimates' was unrelated to performance in the other frontal tests, possibly because it may reflect pathology at a different frontal site. There was no evidence in this study that variability in release from proactive interference was related to measures of frontal function in either patient group, and the conditions under which these patient groups fail to show 'normal' release appear to be tightly constrained. On the other hand, the defective retrieval of retrograde memories was correlated with frontal dysfunction in both patient groups. There was a suggestion of a double dissociation with a measure of nonverbal short-term forgetting, impairment at which was related to the degree of general cortical atrophy rather than frontal dysfunction. A stepwise regression equation based on 3 frontal tests could account for 64% of the variability in retrograde memory performance within the total patient group, 68.5% in the Korsakoff group and 57% in the Alzheimer group. By comparison, the severity of anterograde memory impairment predicted only 21% of the variance in retrograde memory performance. It is concluded that frontal dysfunction produces a disorganization of retrieval processes which contributes to the temporally-extensive retrograde amnesia of these two disorders.