Metabolic correlate of memory-deficit awareness in dementia with Lewy bodies: Implication in cortical midline structure

The neural substrate of memory-deficit awareness has been studied in mild cognitive impairment and Alzheimer's disease (AD). However, little is known about that in dementia with Lewy bodies (DLB). To determine the neural substrates of memory-deficit awareness in DLB, we investigated the relationship between awareness of memory-deficit and glucose metabolism in DLB. Thirty-four patients with DLB were assessed by 18F-FDG-PET and dopamine transporter (DAT)-SPECT. The awareness was evaluated using an awareness index that represents the discrepancy between objective and subjective memory scores. The association between awareness index and FDG uptake was analyzed using SPM12. Awareness index was significantly lower in DLB than in individuals with normal cognition and was associated with glucose metabolism in the bilateral posterior cingulate cortex and right orbitofrontal cortex. Moreover, the awareness index positively correlated with the cingulate island sign ratio but not with striatal DAT density. The findings suggested that the awareness of memory-deficit in DLB was to some extent impaired and its neural substrate was located in cortical midline structure. The concomitant AD-type pathology might have influenced memory-deficit awareness in DLB.