Analysis of error types in the Trail Making Test evidences an inhibitory deficit in dementia of the Alzheimer type

Several studies have reported low performances of patients with dementia of the Alzheimer Type (DAT) on the Trail Making Test (TMT), however, these studies were not designed to identify specific operations underlying this impairment. To better understand the attentional disorder in DAT, we analyzed the performances of patients with DAT and matched elderly adults on the TMT, with a detailed analysis of error types. The analysis showed that 67% of patients' errors were related to an inhibitory deficit versus only 24% in normal elderly adults. Therefore, it was suggested that inefficient inhibitory mechanisms are responsible, to a large extent, for the poor TMT performance of patients with DAT, supporting the hypothesis of an inhibitory dysfunction in DAT.