Apathy and Attentional Biases in Alzheimer's Disease

Background: Apathy, one of the most prevalent neuropsychiatric symptoms in Alzheimer's disease (AD), can be difficult to assess as cognition deteriorates. There is a need for more objective assessments that do not rely on patient insight, communicative capacities, or caregiver observation. Objective: We measured visual scanning behavior, using an eye-tracker, to explore attentional bias in the presence of competing stimuli to assess apathy in AD patients. Methods: Mild-to-moderate AD patients (Standardized Mini-Mental Status Examination, sMMSE > 10) were assessed for apathy (Neuropsychiatric Inventory [NPI] apathy, Apathy Evaluation Scale [AES]). Participants were presented with 16 slides, each containing 4 images of different emotional themes (2 neutral, 1 social, 1 dysphoric). The duration of time spent, and fixation frequency on images were measured. Results: Of the 36 AD patients (14 females, age = 78.2 +/- 7.8, sMMSE= 22.4 +/- 3.5) included, 17 had significant apathy (based on NPI apathy = 4) and 19 did not. These groups had comparable age and sMMSE. Repeated-measures analysis of covariance models, controlling for total NPI, showed group (apathetic versus non-apathetic) by image (social versus dysphoric) interactions for duration (F-1,F-32 = 4.31, p = 0.046) and fixation frequency (F-1,F-32 = 11.34, p = 0.002). Apathetic patients demonstrated reduced duration and fixation frequency on social images compared with non-apathetic patients. Additionally, linear regression models suggest that more severe apathy predicted decreasing fixation frequency on social images (R-2 = 0.26, Adjusted R-2 = 0.19, F-3,F-32 = 3.65, p = 0.023). Conclusion: These results suggest that diminished attentional bias toward social-themed stimuli is a marker of apathy in AD. Measurements of visual scanning behavior may have the potential to predict and monitor treatment response in apathy.