Summary

Using computerized neuropsychological tests of nonverbal visual recognition memory and attention/planning (which require intact temporal and fronto-striatal circuitry respectively), we have obtained evidence to support the view that senile dementias of Alzheimer's (SDAT) and Lewy body (SDLT) type can be distinguished from each other. The main conclusions reviewed here are that while both SDAT and SDLT patients suffer severe mnemonic deficiencies, which reflect degeneration of temporal lobe structures, SDLT patients have, in addition, attentional impairments which could arise from damage to dopaminergic frontostriatal mechanisms. In this latter respect, the cognitive aspects of the SDLT disorder resemble those seen in Parkinson's disease (PD) patients and others with frontal lobe dysfunctions.

Introduction

This review does not need to begin with a description of Lewy body dementia; the numerous reports in this book bear testimony to growing research interest in this disease. The aim is to provide a neuropsychological contribution to these efforts. But what can neuropsychology offer? By studying alterations in specific cognitive abilities under controlled conditions in a large group of subjects, we can obtain a precise idea of the nature of cognitive decline in the disorder and contrast it with related diseases such as senile dementia of the Alzheimer type. Moreover, experimental studies – usually on animal subjects – have, over many years, provided us with a great deal of evidence as to which neural pathways mediate what cognitive processes. Thus, neuropsychological studies can help pinpoint the neuroanatomical focus of a given cognitive dysfunction.