Confabulations in remembering past and planning future are associated with psychiatric symptoms in Alzheimer''s disease

Psychiatric symptoms such as delusions and aggression are frequently observed in patients with Alzheimer's disease (AD), but few studies examined the association of these symptoms with confabulations. We studied 32 AD patients and 10 age- and education-matched healthy older adults. The AD patients were divided into delusion/aggression and non-delusion/non-aggression groups based on their behavioral pathology in AD frequency-weighted severity scale score. Confabulations were assessed using questions about temporality (personal past, orientation, and future planning), and cognitive functions were determined using the mini-mental state examination and the cognitive abilities screening instrument. The AD patients showed confabulations on all types of questions, and their confabulation scores for the past and future were strongly correlated. Cognitive functions were not significantly correlated with confabulation scores for any type of questions. The delusion/aggression group had significantly more confabulations on past and future questions compared to the non-delusion/non-aggression group. These findings suggested that confabulations in remembering the past and planning the future were affected by psychiatric symptoms such as delusion and aggression.     

When true memory availability promotes false memory: evidence from confabulating patients

We explored the extent to which confabulators are susceptible to false recall and false recognition, and whether false recognition is reduced when memory for studied items is experimentally enhanced. Five confabulating patients, nine non-confabulating amnesics--including patients with (F amnesics) and without frontal-lobe dysfunction (NF amnesics)--and 14 control subjects underwent the DRM paradigm [Roediger, H. L., & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory and Cognition, 21, 803-814.] in two experimental conditions. In both conditions participants studied eight lists of semantic associates, and free recall was tested after the presentation of each list. In the Standard condition recognition was tested after the presentation of all the lists, whereas in the Proximal condition patients were administered a six-item recognition task after the presentation of each list. Participants also provided remember or know judgements, and described the content of their recollections. All groups of patients recalled a lower proportion of targets and critical lures than did control subjects, but confabulators recalled more words unrelated to the studied lists than did NF amnesics and controls. All groups of participants improved true recognition across conditions. However, whereas normal controls suppressed false recognition to critical lures in the Proximal compared to the Standard condition, and non-confabulating amnesics showed comparable gist-based false recognition, confabulators showed increased levels of false recognition to critical lures across conditions. Furthermore, NF amnesics significantly reduced false recognition to unrelated lures in the Proximal compared to the Standard condition, whereas confabulators were unable to suppress false recognition to unrelated lures across conditions. Analysis of the phenomenological experience showed that, unlike non-confabulating amnesics, confabulators characterized true and false memories with irrelevant information related to test items. Results are interpreted in light of confabulators' monitoring deficits.     

Intrusions and provoked and spontaneous confabulations on memory tests in Korsakoff’s syndrome

Introduction: Intrusions on verbal memory tests have been used as an index for clinical confabulation. Severe memory impairments in combination with executive dysfunction have been suggested to be the underlying mechanism of confabulation, but to date, this relation is unclear. The aim of this study was (a) to examine the relation between (different types of) intrusions and confabulations in a large sample of confabulating patients with Korsakoff’s syndrome (KS) and (b) to investigate whether different measures of executive functioning and memory performance are related to provoked and spontaneous confabulation. Method: The Dutch version of the California Verbal Learning Test (CVLT) and various executive function and memory tests were administered to a group of 51 confabulating patients with KS. Professional caregivers rated the severity of provoked and spontaneous confabulation behavior of the patients using the Nijmegen–Venray Confabulation List–20 (NVCL–20). Results: The total number of intrusions on the CVLT was not related to either provoked or spontaneous confabulation scores. None of the CVLT intrusion scores correlated significantly with any of the confabulation scores, but we did find small-to-medium, positive correlations between unrelated intrusions and both provoked confabulations and spontaneous confabulation. Provoked confabulation behavior was associated with executive dysfunction and poorer memory performances. Spontaneous confabulation was not related to performance on measures of executive function and memory. Conclusions: The total number of intrusions on verbal memory tests and clinical confabulations appear to be different phenomena. Only unrelated intrusions produced on the CVLT might possibly be related to confabulations. The production of provoked, but not spontaneous, confabulation is associated with executive dysfunction and memory deficits.     

"Do you remember what you did on March 13, 1985?" A case study of confabulatory hypermnesia

We report on a patient, LM, with a Korsakoff's syndrome who showed the unusual tendency to consistently provide a confabulatory answer to episodic memory questions for which the predicted and most frequently observed response in normal subjects and in confabulators is "I don't know". LM's pattern of confabulation, which we refer to as confabulatory hypermnesia, cannot be traced back to any more basic and specific cognitive deficit and is not associated with any particularly unusual pattern of brain damage. Making reference to the Memory, Consciousness and Temporality Theory - MCTT (Dalla Barba, 2002), we propose that LM shows an expanded Temporal Consciousness - TC, which overflows the limits of time ("Do you remember what you did on March 13, 1985?") and of details ("Do you remember what you were wearing on the first day of summer in 1979?") that are usually respected in normal subjects and in confabulating patients.     

Self-serving confabulation in prose recall

Recent studies suggest that the content of confabulation is mainly positive and self-enhancing. In this group study, we aimed to investigate whether this positive bias is specific to self-referent information. Confabulating amnesic patients, amnesic non-confabulating patients and healthy controls were asked to reproduce a series of short stories. We manipulated the emotional valence of the material by including positive, negative and neutral story plots. We also manipulated the self-reference of the material by including self-referent versus other-referent encoding instructions.

Confabulating patients were as impaired as a group of amnesic patients in the amount of information they recalled, both groups being worse than healthy controls. Importantly, confabulating patients showed a selective bias in the negative self-referent condition, in that they recalled such information in a manner which portrayed a more positive image of themselves. This positive bias was not present in stories that were not encoded in a self-referent manner and it was not significantly correlated to patients’ self-reported mood. We propose that both confabulation and its motivated content result from a deficit in the control and regulation of memory retrieval, which allows motivational factors to acquire a greater role than usual in determining which memories are selected for retrieval. To this extent, the self-enhancing content of confabulation could be explained as a neurogenic exaggeration of normal self-serving memory distortion.     

Distinct roles for lateral and medial rostral prefrontal cortex in source monitoring of perceived and imagined events

Rostral prefrontal cortex (PFC) is known to be involved in source memory, the ability to recollect contextual information about an event. However it is unclear whether subregions of rostral PFC may be differentially engaged during the recollection of different kinds of source detail. We used event related functional MRI to contrast two forms of source recollection: (1) recollection of whether stimuli had previously been perceived or imagined, and (2) recollection of which of two temporally distinct lists those stimuli had been presented in. Lateral regions of rostral PFC were activated in both tasks. However medial regions of rostral PFC were activated only when participants were required to recollect source information for self-generated, “imagined” stimuli, indicating a specific role in self-referential processing. In addition, reduced activity in a region of medial ventro-caudal PFC/basal forebrain was associated with making “imagined-to-perceived” confabulation errors. These results suggest that whilst the processing resources supported by some regions of lateral rostral PFC play a general role in source recollection, those supported by medial rostral PFC structures may be more specialised in their contributions.     

Susceptibility to false memories in patients with ACoA aneurysm

We examined ACoA patients regarding their susceptibility to a range of false memory phenomena. We targeted provoked confabulation, false recall and false recognition in the Deese-Roediger-McDermott-paradigm (DRM-paradigm) as well as false recognition in a mirror reading task. ACoA patients produced more provoked confabulations and more false recognition in mirror reading than comparison subjects. Conversely, false recall/false recognition in the DRM-paradigm were similar in patients and controls. Whereas the former two indices of false memories were correlated, no relationship was revealed with the DRM-paradigm. Our results suggest that rupture of ACoA aneurysm leads to an increased susceptibility to a subset of false memories types.     

Spontaneous confabulation, reality monitoring, and the limbic system — a review

Patients with anterior limbic damage may present a distinct syndrome, spontaneous confabulation: they fail in common memory tests, act on the basis of previous habits rather than currently relevant memories, produce confabulations composed of elements of past true events, are disorientated, and are absolutely convinced about the veracity of their perceived reality. Spontaneous confabulation is independent of other false memories, such as, provoked confabulations or illusory recognition. Studies showed that spontaneous confabulators fail to suppress (inactivate) evoked memories that do not pertain to ongoing reality. Rehabilitation differs from other memory failures. Prognosis depends on the lesion site, but recovery is always associated with recovery of this suppression capacity. Lesions typically involve the posterior medial orbitofrontal cortex or its connections in the basal forebrain. Imaging and evoked potential studies in healthy subjects support the idea that the anterior limbic system provides a reality monitoring mechanism which selects memories of current relevance by suppressing (inactivating) currently irrelevant memories. This mechanism appears to adjust the cortical representation of activated memories before their content is recognised and consolidated. Comparison with animal studies suggests that human reality monitoring is a property of the brain’s reward system.