Heterogeneity of semantic and visuospatial deficits in early Alzheimer's disease

Staging of visuospatial and semantic deficits in patients with dementia of the Alzheimer type (DAT) was examined. The authors hypothesized that semant ic ability would be more impaired in these patients, reflecting predominant temporal pathology early in the disease. However, in the Ist study (n = 26 ), 3 patients (11.5%) had marked visual but no semantic impairment. This fi nding was extended in a 2nd study with a 2nd patient sample (n = 21) and mo re specific tasks. Two patients (9.5%) again had visual but no semantic imp airment. These studies confirm that, in patients with DAT presenting with r elatively focal deficits, visual deficits sometimes occur before semantic p roblems. The findings are discussed with regard to the cognitive demands an d neuroanatomical underpinning of the tests used and point to the necessity of using cognitively specific tests to enable accurate analysis of deficit s in the context of the neuroanatomical basis of impairment.