Perirhinal cortex is associated with fine-grained discrimination of conceptually confusable objects in Alzheimer’s disease

The perirhinal cortex (PrC) stands among the first brain areas to deteriorate in Alzheimer’s disease (AD). Many efforts have been made to understand its role in different cognitive functions, to eventually identify early cognitive markers of AD. Based on recent research, the present paper tests to what extent the PrC is involved in representing and discriminating confusable objects based on the conjunction of their perceptual and conceptual features. To this aim, AD patients and control counterparts performed three tasks: a naming task, a recognition memory task, and a conceptual matching task, where we manipulated conceptual confusability and, in the recognition memory task, perceptual confusability. In addition, a high-resolution structural MRI of the antero-lateral parahippocampal subregions was obtained for each participant. The main results were that the sensibility to conceptual confusability was associated with the left PrC volume in both AD patients and control participants for the recognition memory task, while it was specifically associated with the volume of the left PrC in AD patients for the conceptual matching task. This suggests that a decreased volume of the PrC is related to the ability to disambiguate conceptually confusable items. Therefore, testing recognition memory or conceptual matching of easily conceptually confusable items can provide a potential cognitive marker of PrC atrophy.