Background: The neurologic background of confabulations with reference to delusions or cognitive functions has not been clarified in Alzheimer disease (AD).
Methods: Confabulations of 41 AD patients and 12 healthy controls were studied using the Modified Confabulation Battery. The mini-mental state examination and Cognitive Abilities Screening Instrument were used for cognitive evaluations. Cerebral atrophy was assessed by voxel-based–morphometry of magnetic resonance imaging and the correlations with confabulations were analyzed by statistical parametric mapping 2. For the relations with delusion, the AD patients were divided into the delusion and nondelusion groups. The single photon emission computed tomography was performed to evaluate cerebral blood flow and the group difference was analyzed by statistical nonparametric mapping 3.
Results: The AD patients exhibited more confabulations on episodic memory questions compared with semantic questions. The semantic confabulation scores correlated with mini-mental state examination and most Cognitive Abilities Screening Instrument domains scores, and correlated with atrophy in the anterior cingulate, bilateral medial temporal, and right middle temporal gyrus. The delusion group exhibited more episodic confabulations and had lower prefrontal blood flow than the nondelusion group.
Conclusions: Different mechanisms are involved in confabulations between semantic and episodic memories in AD. Episodic confabulation is affected by delusion related to frontal dysfunction, and semantic confabulation is associated with cognitive dysfunction.