Apraxia profiles predict general cognitive deficits in patients with biomarker-verified Alzheimer's pathology

Apraxia represents a core feature of Alzheimer's disease, a neurodegenerative disorder associated with increased β-amyloid plaques and tau deposition. However, descriptions of apraxic deficits in AD patients are still scarce. Here, we comprehensively investigate apraxia profiles and their impact on general cognitive deficits in patients with biomarker-verified Alzheimer's pathology. We characterized the frequency and patterns of apraxic deficits in patients with biomarker-verified Alzheimer's pathology (n=45) using a battery of standardized apraxia tests. Demographic variables and apraxia scores were related to patients' general cognitive impairment using hierarchical regression analyses. Apraxic deficits were found in 78% of patients with biomarker-verified Alzheimer's pathology. AD patients were more impaired in imitating finger gestures (than hand gestures: 76.6% vs. 87.8%, p < 0.001), and imitating complex hand movements (than single hand movements: 76.3% vs. 96.7%, p < 0.001), even when controlling for general cognitive impairment. Apraxia assessments explained about 60% of the variance related to the severity of general cognitive deficits, with deficits in pantomiming object use (beta coefficient: 0.55, p = 0.017) and imitating finger gestures (beta coefficient: -0.51, p < 0.001) being significant predictors of general cognitive impairment. These findings underline the relevance of apraxia in patients with biomarker- verified Alzheimer's pathology. Data revealed distinct apraxia profiles independent of patients' general cognitive status and showed that praxis performance, especially apraxic deficits in pantomiming the use of objects and imitating finger gestures, predicts general cognitive functioning in Alzheimer's disease.