The SQK: a semantic knowledge questionnaire to specify the severity of semantic deterioration in Alzheimer's disease patients

Abstract

Lexico-semantic difficulties are common in Alzheimer's disease (AD). The bottom-up process theory is today well accepted: superordinate attributes tend to decline slower than subordinate ones. However, a specific issue in semantic memory investigation in AD is to determine the severity of the semantic impairment. Given that the regularity of the semantic disorder in early AD is uncertain, we argue that the constitution of experimental AD groups must consider the semantic deterioration stage. We thus propose a specific semantic knowledge questionnaire (SKQ), based on Laiacona et al.'s work (1993). SKQ was proposed to 49 AD patients and 33 healthy old people. Three experimental AD groups were created, based on the global cognitive deterioration. In a second study, we explore the possibility for early AD to display different semantic deterioration profile. Our results show a significant group effect, a significant type of question effect (superordinate vs subordinate) and a significant interaction effect. Moreover, a significant correlation between the total errors at the SKQ and the MMSE score is observed. Finally, we observe that early AD patients can show different semantic alteration, with mild or very mild semantic deterioration without any differences in the global cognitive alteration. The SKQ seems adapted to highlight the semantic deterioration and the bottom-up process in AD: superordinate information are better preserved than subordinate information. It can also distinguish different semantic deterioration in early AD. Our result clearly show that research on semantic deterioration in early stage of AD must take into account the severity of the semantic alteration.