Numerous studies have found category-specific semantic deficits in Alzheimers disease (AD). Thus far, however, only asmall number of studies have investigated how semantic categories lexicalized by verbs are represented, and how thesecategories might be impaired in AD. We investigated the representation and breakdown of verb knowledge employingdifferent syntactic and semantic classes of verbs in a group of probable AD patients (N=10) and matched controls. Inour main task, we employed movies of events and states depicting verbs belonging to three different classes: causatives,perception/psychological, and movement verbs. These verbs differ with regards to their argument structure, the thematicroles they assign, and their hypothetical semantic templates. Patients had more difficult employing verbs of the percep-tion/psychological class. We suggest that thematic roles play the most important role in verb semantic representations. Wefurther suggest that verbs are not represented by decompositional semantic templates.

Objective

To identify the pathophysiologic mechanisms and clinical significance of anosognosia for cognitive decline in mild cognitive impairment.

Methods

We stratified 468 patients with amnestic mild cognitive impairment into intact and impaired awareness groups, determined by the discrepancy between the patient and the informant score on the Everyday Cognition questionnaire. Voxel-based linear regression models evaluated the associations between self-awareness status and baseline β-amyloid load, measured by [¹⁸F]florbetapir, and the relationships between awareness status and regional brain glucose metabolism measured by [¹⁸F]fluorodeoxyglucose at baseline and at 24-month follow-up. Multivariate logistic regression tested the association of awareness status with conversion from amnestic mild cognitive impairment to dementia.

Results

We found that participants with impaired awareness had lower [¹⁸F]fluorodeoxyglucose uptake and increased [¹⁸F]florbetapir uptake in the posterior cingulate cortex at baseline. In addition, impaired awareness in mild cognitive impairment predicted [¹⁸F]fluorodeoxyglucose hypometabolism in the posterior cingulate cortex, left basal forebrain, bilateral medial temporal lobes, and right lateral temporal lobe over 24 months. Furthermore, participants with impaired awareness had a nearly 3-fold increase in likelihood of conversion to dementia within a 2-year time frame.

Conclusions

Our results suggest that anosognosia is linked to Alzheimer disease pathophysiology in vulnerable structures, and predicts subsequent hypometabolism in the default mode network, accompanied by an increased risk of progression to dementia. This highlights the importance of assessing awareness of cognitive decline in the clinical evaluation and management of individuals with amnestic mild cognitive impairment.