Alzheimer's disease is associated with distinctive semantic feature loss

A central topic of discussion in the exploration of semantic disturbance in Alzheimer's disease (AD) concerns the relative contribution of semantic content (e.g., semantic features) and semantic process. Studies have suggested that semantic dysfunction in AD is the result of deficits to either semantic process, semantic content or both. Studies that have supported the loss of semantic content have been criticised for their use of verbal stimuli and cognitively challenging experimental tasks. The current study used a novel version of the yes-no recognition memory task to compare the processing of distinctive and non-distinctive features in participants with AD whilst controlling the cognitive demands of the task. The task involved five conditions which denoted the relationship between the items in the test and study phase. A 'non-distinctive' and a 'distinctive' condition were included where non-distinctive and distinctive semantic features were manipulated between study and test, respectively. Task accuracy of participants with AD decreased relative to control participants when distinctive features were manipulated between the study and test phase of the experiment. There was no significant difference between groups when non-distinctive features were manipulated. These findings provide evidence to support the loss of semantic content in AD.