New learning and remote memory in atypical Alzheimer's disease.

This paper presents the case of BB, an individual with an atypical posterior cortical presentation of Alzheimer's disease (AD). The severity of BB's visuo-spatial impairment far outweighed impairment of other cognitive functions. BB's case is also unusual in that despite a long history of progressive impairment, his cognitive symptoms remain relatively circumscribed. More specifically, BB's pattern of memory impairment was striking, since his impairment on formal psychometric tests of memory contrasted with his performance at clinical interview, where he talked lucidly about events in his past, and displayed remarkably well-preserved general semantic knowledge. On the basis of BB's clinical profile, it was hypothesised that his pattern of cognitive performance reflected an impairment of anterograde memory in the context of relative preservation of remote memory. Further investigations revealed that while BB's anterograde memory function was comparable to that of other AD patients, his remote memory was well preserved relative to other AD 'controls'. These findings are discussed in terms of typical and atypical presentations of Alzheimer's disease, and in terms of the possible fractionation of different aspects of long-term memory. The implications of these findings for our understanding of the neural bases of different types of retrograde memory (i.e. 'old' versus 'recent') are considered, with particular reference to the contrasting theoretical frameworks that have recently been advanced by Squire and Moscovitch.