Cognitive mechanisms of confabulations in Alzheimer's Disease

BackgroundAlzheimers disease (AD) patients are characterized by an early decline of episodic memory due to hippocampal damage. Nonetheless, besides the classical negative symptoms related to episodic memory deficits, i.e. failure to retrieve information, it has been shown that AD patients can also suffer from positives symptoms, i.e. confabulations. Some theoretical accounts have been proposed to explain the cognitive mechanisms underlying confabulation. Yet, even if most of these models have lead to some research trying to validate cognitive deficits in some cognitive domains, in particular executive functions, to our knowledge, none has yet tried to determine the specific cognitive profile of confabulatory patients. In the present study the main aim is to characterize the specific cognitive profile of confabulatory patients. Thus, given that AD patients cognitive profile is well known and documented, we compare mild to moderate AD patients with and without confabulations. Methods37 healthy control (HC) and 35 individuals with mild to moderate AD were recruited at the Pitie Salpetriere University Hospital. All participants were evaluated on Dalla Barbas Confabulation Battery to determine their tendency to produce provoked confabulations. Thus, among AD patients, we distinguish between those who produced confabulations in episodic memory questions, and those who did not. Accordingly 27 AD patients were considered free of confabulations (ADC-), and 8 as confabulators (ADC+) (none HC met the criteria). All participants were assessed on a comprehensive neuropsychological battery. ResultsStatistical analyses showed a significant difference between HC participants and the two groups of AD patients, in almost all cognitive domains assessed. However, when comparing the two AD groups, they did not show distinct profiles. Moreover, regarding the type of confabulations, ADC+ produced significantly more confabulations to the Episodic questions (both concerning past and future). ConclusionsBy not demonstrating cognitive differences between patients with and without confabulations, our results cast doubts on some confabulation models, which assume a unique and sufficient cognitive (e.g. executive) deficit underlying the onset of confabulations. HighlightsO_LIAlzheimers disease patients with or without confabulations do not have otherwise distinct cognitive profiles. C_LIO_LIThe emergence of a confabulatory syndrome does not seem to be the result of a necessary and sufficient executive deficit C_LIO_LIAlzheimers disease patients mainly produce episodic memory confabulations, which involve both the past and the future dimension. C_LI