Relationship of frontal lobe dysfunction and aberrant motor behaviors in patients with Alzheimer's disease

Background: In order to address the neuropsychological pathogenesis of aberrant motor behaviors in Alzheimer's disease (AD), we used a cross-sectional study design to investigate the association between frontal lobe function, including executive function, and activity disturbances (wandering, purposeless activities and inappropriate activities). Methods: Among 75 consecutive outpatients with AD, 50 subjects with a Clinical Dementia Rating (CDR) score of 1 or 2 were selected and divided into two groups based on data obtained from interviews with their caregivers: an aberrant motor behaviors (AMB) group (n = 22), and a non-aberrant motor behaviors (NAMB) group (n = 28). Aberrant motor behavior was defined according to whether the "activity disturbance" score (ranging from 0 to 9) of the Behavioral Pathology in Alzheimer Disease (Behave-AD) scale was 0 or >= 1. The total and subtest scores of the Frontal Assessment Battery (FAB) were then compared between the two groups. Results: Significant differences were found between the FAB total (P < 0.05) and the subtest scores (lexical fluency, conflicting instructions; P < 0.05) in the two groups. The FAB score was significantly associated with the activity disturbance score (r = -0.49; P<0.001). A stepwise multiple regression analysis showed that only the FAB score significantly influenced the activity disturbance score (P < 0.001). Conclusions: This finding suggested that in addition to episodic memory disturbance, frontal lobe dysfunctions might lead patients with AD to develop aberrant motor behavior.