Category-specific semantics in Alzheimer's dementia and normal aging?

Category-specific deficits represent the archetypal illustration of domain-specific cognitive processes. These deficits describe individuals who, following certain types of neurological damage show dissociations in their ability to recognise and name exemplars from within specific domains e.g. living or nonliving things. Cases described over the past 25 years have formed a pivotal foundation for the development of models describing the structure and organisation of lexical-semantic memory. In this chapter, we review the evidence on whether category deficits in AD are consistent with the loss of isolated categorical information, an artefact of confounding psycholinguistic variables (e.g. age of acquisition, word frequency, and familiarity) or an exaggeration of some pre-existing normal cognitive difference. Finally, we present emerging evidence that female AD patients show worse semantic memory impairment than male patients. In this context, we discuss a possible role for the apolipoprotein E (APOE) e{open}4 allele, which is associated with a greater probability for developing AD in women and impacts more on the cognitive performance of healthy women than men.