Different patterns of recollection impairment in confabulation reveal different disorders of consciousness: A multiple case study.

Recollection is used to refer to the active process of setting up retrieval cues, evaluating the outcome, and systematically working toward a representation of a past experience that we find acceptable. In this study we report on three patients showing different patterns of confabulation affecting recollection and consciousness differentially. All patients confabulated in the episodic past domain. However, whereas in one patient confabulation affected only recollection of events concerning his personal past, present and future, in another patient confabulation also affected recollection of impersonal knowledge. The third patient showed an intermediate pattern of confabulation, which affected selectively the retrieval of past information, both personal and impersonal. We suggest that our results are in favor of a fractionation of processes involved in recollection underling different disorders of consciousness.

Confabulation in Alzheimer's disease and amnesia: a qualitative account and a new taxonomy.

Clinical and experimental observation have shown that patients who confabulate, especially but not exclusively when provoked by specific questions, retrieve personal habits, repeated events or over-learned information and mistake them for actually experienced, specific, unique events. Accordingly, the aim of this study is to characterize and quantify the relative contribution of this type of confabulation, which we refer to as Habits Confabulation (HC), to confabulations produced by 10 mild Alzheimer's disease (AD) patients and 8 confabulating amnesics (CA) of various etiologies. On the Confabulation Battery (Dalla Barba, 1993a, Dalla Barba & Decaix, 2009), a set of questions involving the retrieval of various kinds of semantic and episodic information, patients produced a total of 424 confabulation. HC accounted for 42% and 62% of confabulations in AD patients and CA, respectively. This result indicates that, regardless the clinical diagnosis, the brain pathology or their lesion's site, confabulation largely reflects the individuals' tendency to consider habits, routines, and over-learned information as unique episodes. These results are discussed in the framework of the Memory Consciousness and Temporality Theory (Dalla Barba, 2002).

Confabulators mistake multiplicity for uniqueness.

Some patients with organic amnesia show confabulation, the production of statements and actions unintentionally incongruous to the subject's history, present and future situation. It has been shown that confabulators tend to report as unique and specific personal memories, events or actions that belong to their habits and routines (Habits Confabulations). We consider that habits and routines can be characterized by multiplicity, as opposed to uniqueness. This paper examines this phenomenon whereby confabulators mistake multiplicity, i.e., repeated events, for uniqueness, i.e., events that occurred in a unique and specific temporo-spatial context. In order to measure the ability to discriminate unique from repeated events we used four runs of a recognition memory task, in which some items were seen only once at study, whereas others were seen four times. Confabulators, but not non-confabulating amnesiacs (NCA), considered repeated items as unique, thus mistaking multiplicity for uniqueness. This phenomenon has been observed clinically but our study is the first to demonstrate it experimentally. We suggest that a crucial mechanism involved in the production of confabulations is thus the confusion between unique and repeated events.