The mechanisms of spontaneous and provoked confabulations

Summary Confabulation is a mysterious adjunct of amnesia. It remains unexplained why some patients invent untrue stories in response to questions (provoked confabulations) or even spontaneously with no apparent motivation (spontaneous confabulations). Hypothesized mechanisms range from a desire to fill gaps in memory to a loss of the temporal context in memory. We examined the mechanisms of confabulations in 16 amnesic patients. Patients were classified as spontaneous confabulators if they ever acted according to their confabulations. Provoked confabulations were measured as the number of intrusions in a verbal learning test. We found a double dissociation between the two types of confabulations, indicating that they represent different disorders rather than different degrees of the same disorder. Confabulating patients did not show an increased tendency to fill gaps in memory as measured by the number of fake questions concerning non existent items that they answered. Neither type of confabulation correlated with a failure to store new information as gauged with recognition tasks; pure information storage was even found to be normal in some patients. However, we found a positive correlation between several measures of verbal learning and verbal fluency with provoked, but not spontaneous, confabulations. In contrast, spontaneous, but not provoked, confabulations were associated with an inability to recognize the temporal order of stored information as measured by the comparison of two runs of a continuous recognition task. We suggest that provoked confabulations depend on an amnesic subject's search in his deficient memory and are the trade-off for increased item recollection. Spontaneous confabulations appear to be based on a failure to recognize the temporal order of stored information, resulting in erroneous recollection of elements of memory that do not belong togethe

Confabulation: damage to a specific inferior medial prefrontal system

Confabulation, the pathological production of false memories, occurs following a variety of aetiologies involving the frontal lobes, and is frequently held to be underpinned by combined memory and executive deficits. However, the critical frontal regions and specific cognitive deficits involved are unclear. Studies in amnesic patients have associated confabulation with damage to the orbital and ventromedial prefrontal cortex. However neuroimaging studies have associated memory control processes which are assumed to underlie confabulation with the right lateral prefrontal cortex. We used a confabulation battery to investigate the occurrence and localisation of confabulation in an unselected series of 38 patients with focal frontal lesions. 12 patients with posterior lesions and 50 healthy controls were included for comparison. Significantly higher levels of confabulation were found in the Frontal group, confirming previous reports. More detailed grouping according to lesion location within the frontal lobe revealed that patients with orbital, medial and left lateral damage confabulated in response to questions probing personal episodic memory. Patients with orbital, medial and right lateral damage confabulated in response to questions probing orientation to time. Performance-led analysis revealed that all patients who produced a total number of confabulations outside the normal range had a lesion affecting either the orbital region or inferior portion of the anterior cingulate. These data provide striking evidence that the critical deficit for confabulation has its anatomical location in the inferior medial frontal lobe. Performance on tests of memory and executive functioning showed considerable variability. Although a degree of memory impairment does seem necessary, performance on traditional executive tests is less helpful in explaining confabulation

Confabulations after Bilateral Consecutive Strokes of the Lenticulostriate Arteries

We describe the case of a 75-year-old woman who manifested persistent confabulations after two consecutive strokes encompassing the area of the lenticulostriate arteries territory on both hemispheres. Findings reported on this rare clinical syndrome suggest that fantastic confabulations and delusional thoughts may arise after bilateral damage of subcortical nonthalamic structures

Behaviorally spontaneous confabulation in limbic encephalitis: The roles of reality filtering and strategic monitoring

Behaviorally spontaneous confabulation is characterized by a confusion of reality evident in currently inappropriate acts that patients justify with confabulations and in disorientation. Here, we describe a 38-year-old woman lawyer hospitalized because of non-herpetic, presumably autoimmune, limbic encephalitis. For months, she considered herself at work and desperately tried to respect her falsely believed professional obligations. In contrast to a completely erroneous concept of reality, she did not confabulate about her remote personal past. In tasks proposed to test strategic retrieval monitoring, she produced no confabulations. As expected, she failed in tasks of reality filtering, previously shown to have high sensitivity and specificity for behaviorally spontaneous confabulation and disorientation: she failed to suppress the interference of currently irrelevant memories and she had deficient extinction capacity. The observation underscores the special status of behaviorally spontaneous confabulation among confabulatory phenomena and of reality filtering as a thought control mechanism. We suggest that different processes may underlie the generation of false memories and their verbal expression. We also emphasize the need to present theories of confabulation together with experimental tasks that allow one to empirically verify the theories and to explore underlying physiological mechanisms. (JINS, 2010, 16, 995-1005.

Fake or Fantasy: Rapid Dissociation between Strategic Content Monitoring and Reality Filtering in Human Memory

Memory verification is crucial for meaningful behavior. Orbitofrontal damage may impair verification and induce confabulation and inappropriate acts. The strategic retrieval account explains this state by deficient monitoring of memories' precise content, whereas the reality filter hypothesis explains it by a failure of an orbitofrontal mechanism suppressing the interference of memories that do not pertain to reality. The distinctiveness of these mechanisms has recently been questioned. Here, we juxtaposed these 2 mechanisms using high-resolution evoked potentials in healthy subjects who performed 2 runs of a continuous recognition task which contained pictures that precisely matched or only resembled previous pictures. We found behavioral and electrophysiological dissociation: Strategic content monitoring was maximally challenged by stimuli resembling previous ones, whereas reality filtering was maximally challenged by identical stimuli. Evoked potentials dissociated at 200-300 ms: Strategic monitoring induced a strong frontal negativity and a distinct cortical map configuration, which were particularly weakly expressed in reality filtering. Recognition of real repetitions was expressed at 300-400 ms, associated with ventromedial prefrontal activation. Thus, verification of a memory's concordance with the past (its content) dissociates from the verification of its concordance with the present. The role of these memory control mechanisms in the generation of confabulations and disorientation is discusse

Human Processing of Behaviorally Relevant and Irrelevant Absence of Expected Rewards: A High-Resolution ERP Study

Acute lesions of the posterior medial orbitofrontal cortex (OFC) in humans may induce a state of reality confusion marked by confabulation, disorientation, and currently inappropriate actions. This clinical state is strongly associated with an inability to abandon previously valid anticipations, that is, extinction capacity. In healthy subjects, the filtering of memories according to their relation with ongoing reality is associated with activity in posterior medial OFC (area 13) and electrophysiologically expressed at 220–300 ms. These observations indicate that the human OFC also functions as a generic reality monitoring system. For this function, it is presumably more important for the OFC to evaluate the current behavioral appropriateness of anticipations rather than their hedonic value. In the present study, we put this hypothesis to the test. Participants performed a reversal learning task with intermittent absence of reward delivery. High-density evoked potential analysis showed that the omission of expected reward induced a specific electrocortical response in trials signaling the necessity to abandon the hitherto reward predicting choice, but not when omission of reward had no such connotation. This processing difference occurred at 200–300 ms. Source estimation using inverse solution analysis indicated that it emanated from the posterior medial OFC. We suggest that the human brain uses this signal from the OFC to keep thought and behavior in phase with reality

Effectiveness of a neuropsychological treatment for confabulations after brain injury: A clinical trial with theoretical implications

The study is part of a doctoral dissertation by Estrella Ródenas, supervised by the other three authors.Confabulators consistently generate false memories without intention to deceive and with great feelings of rightness. However, to our knowledge, there is currently no known effective treatment for them. In order to fill this gap, our aim was to design a neuropsychological treatment based on current theoretical models and test it experimentally in 20 confabulators sequentially allocated to two groups: an experimental and a control group. The experimental group received nine sessions of treatment for three weeks (three sessions per week). The sessions consisted of some brief material that participants had to learn and recall at both immediate and delayed time points. After this, patients were given feedback about their performance (errors and correct responses). Pre- and post-treatment measurements were recorded. Confabulators in the control group were included in a waiting list for three weeks, performed the pre- and post- measurements without treatment, and only then received the treatment, after which a post-treatment measurement was recorded. This applied to only half of the participants; the other half quit the study prematurely. Results showed a significant decrease in confabulations and a significant increase in correct responses in the experimental group; by contrast, patients in the control group did not improve during the waiting list period. Only control group patients who subsequently received the treatment after serving as controls improved. The effects of the treatment were generalized to patients’ everyday lives, as reported by relatives, and persisted over time. This treatment seems to be effective and easy to implement and consequently of clinical interest. Moreover, it also has theoretical implications regarding the processes related to the genesis and/or maintenance of confabulations. In particular, results point to a deficit in early stages of memory retrieval with the preservation of later strategic monitoring processes. Specifically, some of the processes involved may include selective attention or early conflict detection deficits. Future research should test these hypotheses.This research was carried out in San Rafael University Hospital in Granada, Spain, and was supported by the research grants from the Spanish Ministry of Science and Education to Juan Lupiáñez (PSI2011-22416 and PSI2014-52764-P) and to María Jesús Funes (PSI2012-34158), the research grant from the Regional Government of Andalusia to María Jesús Funes (SEJ-6351), and the research grant from the Progress and Health Foundation of the Regional Government of Andalusia to Mónica Triviño (PI-0361-2014)

When Rey-Osterrieth's Complex Figure Becomes a Church: Prevalence and Correlates of Graphic Confabulations in Dementia

Verbal confabulation (VC) has been described in several pathological conditions characterized by amnesia and has been defined as ‘statements that involve distortion of memories’. Here we describe another kind of confabulation (graphic confabulation, GC), evident at the recall of the Rey-Osterrieth complex figure (ROCF). In a retrospective study of 267 patients with mild-to-moderate dementia, 14 patients (4.9 %) recalled the abstract ROCF as drawings with recognizable semantic meaning. VC was evident at the story recall test in 19.8% of the study participants. VC and GC were homogeneously distributed among the different types of dementia. VC has been proposed to originate from complex interactions of amnesia, motivational deficit and dysfunction of monitoring systems. On the contrary, GC seems to be the result of a deficit in visual memory replaced by the semantic translation of isolated parts of the ROCF along with a source monitoring deficit