Executive function deficits in patients with dementia of the Alzheimer’s type: A study with a Tower of London task

A growing number of studies report a deterioration of the executive function (EF) in dementia of the Alzheimer type (DAT). To evaluate EFs in DAT, a new version of the Tower of London (TOL) task, originally developed by Shallice (1982), was adapted. The new version of the test was built up in its easiest possible feature in order to be administrable to early- or middle-stage demented patients. Seventeen DAT patients, and 17 controls matched for age and sex, were administered the TOL. The protocol followed a “hierarchical paradigm,” that is, simpler problems were embedded in more complex, subsequent problems. Results showed that DAT patients were impaired compared to controls. Both control and DAT groups showed a decrease in percentage of success rate in relation to the number of movements required by the task. On the more complex problems, the performance of DAT subjects was proportionally more impaired. Qualitative analysis revealed that rule breaking was a salient performance feature of the DAT group. These findings are consistent with the presence of an EF deficit in DAT.