Brain Advance Access originally published online on October 1, 2008
Brain 2009 132(1):204-212; doi:10.1093/brain/awn241
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Confabulation in Alzheimer's disease: poor encoding and retrieval of over-learned information
1 INSERM Unit 610, Paris 2 Université Pierre et Marie Curie-Paris 6, Paris 3 AP-HP, Hôpital de la Salpêtrière, Fédération de Neurologie, Paris 4 AP-HP, Hôpital Henri Mondor, Service de Neurologie, Créteil, France 5 Dipartimento di Psicologia, Università degli Studi di Trieste, Trieste, Italy
Correspondence to: Gianfranco Dalla Barba, MD, PhD, INSERM Unit 610, Pavillon Claude Bernard, Hôpital de la Salpêtrière, 47, bd de l'Hôpital, 75013 Paris, France E-mail: dallabarba{at}chups.jussieu.fr
Patients who confabulate retrieve personal habits, repeated events or over-learned information and mistake them for actually experienced, specific unique events. Although some hypotheses favour a disruption of frontal/executive functions operating at retrieval, the respective involvement of encoding and retrieval processes in confabulation is still controversial. The present study sought to investigate experimentally the involvement of encoding and retrieval processes and the interference of over-learned information in the confabulation of Alzheimer's disease patients. Twenty Alzheimer's disease patients and 20 normal controls encoded and retrieved unknown stories, well-known fairy tales (e.g. Snow White) and modified well-known fairy tales (e.g. Little Red Riding Hood is not eaten by the wolf) under three experimental conditions: (i) full attention at encoding and at retrieval; (ii) divided attention at encoding (i.e. performing an attention demanding secondary task) and full attention at retrieval; (iii) full attention at encoding and divided attention at retrieval. We found that confabulations in Alzheimer's disease patients were more frequent for the modified well-known fairy tales and when encoding was weakened by a concurrent secondary task (61%), compared with the other types of stories and experimental conditions. Confabulations in the modified fairy tales always consisted of elements of the original version of the fairy tale (e.g. Little Red Riding Hood is eaten by the wolf). This is the first experimental evidence showing that poor encoding and over-learned information are involved in confabulation in Alzheimer's disease.
Key Words: Alzheimer's disease; confabulation; memory; encoding; retrieval
Abbreviations: DA, divided attention; FA, full attention; NC, normal control; RT, reaction time
Received June 13, 2008. Revised August 29, 2008. Accepted September 5, 2008.