Forms of confabulation: Dissociations and associations

Confabulation denotes the emergence of memories of experiences and events which never took place. Whether there are distinct forms with distinct mechanisms is still debated. In this study, we explored 4 forms of confabulation and their mechanisms in 29 amnesic patients. Patients performed tests of explicit memory, executive functions, and two test of orbitofrontal reality filtering (memory selection and extinction capacity in a reversal learning task) previously shown to be strongly associated with confabulations that patients act upon and disorientation. Results indicated the following associations: (1) Intrusions in a verbal memory test (simple provoked confabulations) dissociated from all other forms of confabulation and were not associated with any specific cognitive measure. (2) Momentary confabulations, defined as confabulatory responses to questions and measured with a confabulation questionnaire, were associated with impaired mental flexibility, a tendency to fill gaps in memory, and with one measure of reality filtering. Momentary confabulations, therefore, may emanate from diverse causes. (3) Behaviourally spontaneous confabulation, characterized by confabulations that the patients act upon and disorientation, was strongly associated with failure in the two reality filtering tasks. Behaviourally spontaneous confabulation may be seen as a specific instance of momentary confabulations with a distinct mechanism. (4) A patient producing fantastic confabulations with nonsensical, illogical content had wide-spread cognitive dysfunction and failed in the reality filtering tasks. The results support the presence of truly or partially dissociable types of confabulation with different mechanisms.     

Disturbance of time orientation,attention, and verbal memory in amnesic patients with confabulation

Confabulation is often observed in amnesic patients after brain damage. However, evidence regarding the relationship between confabulation and other neuropsychological functions is scarce. In addition, previous studies have proposed two possibilities of the relationship between confabulation and false memory, in which patients with confabulation are likely to retrieve false memories, or confabulations are relatively independent of false memories. The present study investigated how confabulation is related to various cognitive functions, including orientation, attention, frontal lobe function, memory, and mental status, and to false memories, as assessed by the Deese–Roediger–Mcdermott (DRM) paradigm. Patients with organic amnesia participated, and confabulations were evaluated using the Confabulation Battery. Amnestic patients were classified into two groups: confabulating (CP) and nonconfabulating patients (NCP). The CP group was significantly impaired in time orientation, attention, and verbal memory, compared to the NCP group and age-matched healthy controls (HC). Results of the DRM paradigm revealed no significant difference in false memory retrieval induced by critical lures across CP, NCP, and HC groups. Confabulating responses in organic amnesia could be in part induced by disturbance of time consciousness and attention control in severe impairment of verbal memories, and confabulation and false memory could be modulated by different cognitive systems.     

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.     

Diagnosis-specific effect of familial loading on verbal working memory in schizophrenia

Background  Working memory disturbances are a frequently replicated finding in schizophrenia and less consistent also in schizoaffective disorder. Working memory dysfunctions have been shown to be heritable and have been proposed to represent a promising endophenotype of schizophrenic psychoses. Methods   In the present study, we investigated the effects of familial loading on performance rates in circuit-specific verbal and visuospatial working memory tasks in matched samples of schizophrenic patients (from multiply affected or uniaffected families), schizoaffective patients (from multiply affected or uniaffected families), and healthy subjects. Results  We found a significant interaction effect between familial loading and diagnosis in terms of a diagnosis-specific detrimental effect of familial loading on the performance of schizophrenic (but not schizoaffective) patients in the articulatory rehearsal task. Conclusion  This finding of a circuit-specific verbal working memory deficit in schizophrenic patients with additional familial loading is consistent with prior studies, which provided evidence for the existence of specific subgroups of schizophrenic patients with selective working memory impairments and for diagnosis-specific dysfunctions of the articulatory rehearsal mechanism in schizophrenic, but not in schizoaffective patients. Together, these findings suggest that the genetic risk for (a subtype of) schizophrenia may be associated with dysfunctions of the brain system, which underlies the articulatory rehearsal mechanism, the probably phylogenetically youngest part of human working memory.     

Memory performance of geriatric and nongeriatric chronic schizophrenic patients: a cross-sectional study.

Memory functioning has been studied extensively in nongeriatric schizophrenic patients, leading to the suggestion that schizophrenic patients manifest a "subcortical" pattern of memory deficits. Few previous studies examined very poor outcome patients with a chronic course of hospitalization. This study examined the association of age and global cognitive dysfunction with verbal and spatial learning and delayed recall, as well as examining differential impairments in delayed recall as compared to delayed recognition memory. Sixty-six chronic schizophrenic patients were studied, with 30 of these patients over the age of 65. Verbal (California Verbal Learning Test) and spatial (Biber Figure Learning Test) serial learning and delayed memory tests were administered. All aspects of memory functioning were correlated with estimates of global cognitive status. When global cognitive status was controlled, age effects were still found for the majority of the memory measures. Delayed recognition memory was not spared, being performed as poorly as delayed recall. In contrast to previous studies of better-outcome patients with schizophrenia, geriatric patients with chronic schizophrenia performed more poorly than nongeriatric patients. The lack of sparing of delayed recognition memory suggests that previous findings of specific recall memory deficit and a subcortical profile of memory impairments may apply to schizophrenic patients with less severe global cognitive impairments. These data suggest that poor-outcome patients may have a pattern of memory impairments that has some features in common with cortical dementia.     

An analysis of the specificity and the syndromal correlates of verbal memory impairments in schizophrenia

It was investigated whether schizophrenic and depressive patients show a distinguishable mnestic profile. A further aim was to explore the psychopathological correlates of memory malperfomance in schizophrenic patients. For the present study, schizophrenic, depressive and healthy samples (n=25 each) were compared regarding their performance in the Rey Auditory Verbal Learning Test. Subjects' sociodemographic background variables were comparable except for age (entered as a covariate). Depressive and schizophrenic patients performed significantly worse than healthy controls regarding both short-term and long-term free recall as well as recognition. No differences occurred for two parameters reflecting proneness to interference. Negative schizophrenic symptomatology was strongly correlated with memory dysfunction before and after controlling for distractibility. The study supports previous research suggesting that memory impairments in schizophrenia are not an epiphenomenon of deficits in verbal fluency or an attentional impairment. The major deficit in both schizophrenic and depressive patients is inferred to be the capability to learn.     

Effects of anticholinergic drug withdrawal on memory, regional cerebral blood flow and extrapyramidal side effects in schizophrenic patients

It has been suggested that anticholinergic drugs impair immediate memory and working memory in patients with schizophrenia. Opinions remain divided as to the influence of anticholinergic drug withdrawal on the psychopathology and extrapyramidal side effects (EPS) in these patients. In our previous study, regional cerebral blood flow (rCBF) was reduced in all regions of patients taking anticholinergic drugs. Anticholinergic drugs were withdrawn in 21 schizophrenic inpatients. Immediate and verbal working memory, rCBF, psychopathology, and EPS were investigated before and after anticholinergic withdrawal. There was improvement in immediate memory, verbal working memory, and psychopathology, as well as an increase in rCBF after withdrawal from anticholinergic drugs. EPS showed no significant changes. Factors that may predict the improvement of immediate memory after withdrawal of anticholinergic drugs are more severe baseline psychopathology and use of a higher anticholinergic drug dose at baseline. Improvement of working memory may be predicted by a higher baseline rCBF in the left anterior cerebral artery region. Withdrawal from anticholinergics should be considered in schizophrenic patients, and it is important to taper these drugs over at least four weeks.     

Schizophrenia and Crime: How Predictable Are Charges,Convictions and Violence?

The schizophrenia-crime relationship was studied in 151 research participants meeting DSM-IV criteria for schizophrenia or schizoaffective disorder and with histories positive or negative for criminal charges, convictions and offences involving violence. These crime-related variables were regressed on a block of nine predictors reflecting non-specific illness context (e.g. demographic, social) and a block of 14 predictors reflecting specific illness content (e.g. symptoms). Context variables predicted charges, with unique contributions from employment status, education and substance use. Further significant validity was provided by content-related predictors including symptoms (paranoia, depression, low energy), but not cognitive performance (verbal and non-verbal ability, working memory, processing speed, verbal memory, word fluency, inhibition, practical cognition). In contrast, neither convictions nor violence were predicted by illness context or content variables. These results suggest that specific contextual and intrinsic aspects of schizophrenic illness make interaction with law enforcement and therefore criminal charges more likely.     

Memory in functional psychosis.

Acute schizophrenic, chronic schizophrenic, and depressive patients (20 of each) were compared with normal subjects and six groups of patients with organic brain disease. They were given tests of verbal learning (left hemisphere type function) and pattern recognition memory (right hemisphere type function). All functional psychotics showed impaired memory. Acute schizophrenics were, however, only impaired on the verbal task, suggesting left hemisphere dysfunction, while chronic schizophrenics and depressives were impaired on both tasks, suggesting bilateral dysfunction.     

Verbal recall and recognition in twins discordant for schizophrenia

The nature, neural underpinnings, and etiology of deficits in verbal declarative memory in patients with schizophrenia remain unclear. To examine the contributions of genes and environment to verbal recall and recognition performance in this disorder, the California Verbal Learning Test was administered to a large population-based Finnish twin sample, which included schizophrenic and schizoaffective patients, their non-ill monozygotic (MZ) and dizygotic (DZ) co-twins, and healthy control twins. Compared with controls, patients and their co-twins showed relatively greater performance deficits on free recall compared with recognition. Intra-pair differences between patients and their non-ill co-twins in hippocampal volume and memory performance were highly positively correlated. These findings are consistent with the view that genetic influences are associated with reduced verbal recall in schizophrenia, but that non-genetic influences further compromise these abnormalities in patients who manifest the full-blown schizophrenia phenotype, with this additional degree of disease-related declarative memory deficit mediated in part by hippocampal pathology.     

The continuous performance test, identical pairs version: II. Contrasting attentional profiles in schizophrenic and depressed patients

The Continuous Performance Test-Identical Pairs version was administered to 14 schizophrenic patients, 17 depressed patients, and 28 normal controls. The task was divided into verbal and spatial stimuli, as well as no-distraction and distraction (verbal and auditory) conditions. Both patient groups displayed attentional impairments compared to normal subjects, but they differed from each other in specific profiles. Schizophrenic patients were characterized by a global impairment and a particular inability to focus on the critical stimuli, whether verbal or spatial. They also made an excess of random responses throughout the task but showed no evidence that attention declined from its initial level over time. Depressed patients did not display a global attentional deficit but did show a specific inability to attend to spatial as compared to verbal stimuli and, in particular, a confusion when the spatial stimuli were only slightly different. Performance on a secondary task in response to a change in expectation improved dramatically for depressed but not schizophrenic patients, suggesting a more efficient allocation strategy, a greater reserve of processing capacity, or more dependence on motivational factors in depressed patients. Schizophrenic and depressed patients were alike in extent of distractibility. Whereas normal controls improved with the onset of external distraction, schizophrenic and depressed patients deteriorated to an equal extent. Distractibility was thus concluded to be a correlate of acute psychiatric illness and not specific for schizophrenia.     

Amygdala-hippocampal volume and verbal memory in first-degree relatives of schizophrenic patients

Verbal memory deficits have been related to reduced volume of medial temporal structures in several neurological and psychiatric populations, including schizophrenic patients. Impairments in verbal memory have been proposed to be a marker of risk for schizophrenia. Recently, relatives of schizophrenic patients have been reported to have reduced volume of the amygdala-hippocampal complex. In this study, we evaluate the possibility that amygdala-hippocampal volume reductions may constitute one neural substrate of verbal memory deficits in first-degree relatives. Subjects were 20 healthy first-degree relatives of schizophrenic patients and 14 demographically similar controls. Verbal memory was assessed with the Logical Memory Test. Subjects were scanned with high-resolution MRI and the images were transformed into Talairach space. Volumes of interest were amygdala-anterior hippocampus and posterior hippocampus. Relatives of schizophrenic patients had intact immediate verbal memory but significantly poorer delayed verbal memory than controls. Relatives also had significantly reduced amygdala-anterior hippocampus volumes. Across all subjects, delayed verbal memory was significantly correlated with amygdala-anterior hippocampus volume. The magnitude of the correlation did not differ between the groups. These data provide an empirical link between memory performance and volumetric abnormalities in the amygdala-hippocampal complex in the relatives of schizophrenic patients.     

A comparison of verbal fluency tasks in schizophrenic patients and normal controls

Previous studies have reported significant impairment on verbal fluency tasks (semantic and letter) among schizophrenic subjects. However, the possibility of specific categorical deficits has not been adequately investigated. Nor have the effects of task duration, the stability between testing sessions, and the relationship between intelligence and performance on fluency been thoroughly studied. We performed a series of 3 min fluency tasks (semantic/syntactic and letter) to determine whether duration specific or category-specific differences exist between schizophrenic subjects and normal controls. Each subject was tested at three different times as a means of estimating word pool and assessing the stability of fluency output. Subjects were asked to generate exemplars from each of four semantic/syntactic categories (animals, tools, common nouns and verbs) and three letters (G, E and T). Data from 13 schizophrenic subjects and 15 sex-, age- and pre-morbid-IQ-matched control subjects revealed that patients' overall performance on both the semantic and letter fluency tasks was impaired. While differential impairment on specific semantic categories was noted between groups, no differential effects relating to task duration or testing session were present. Further, by comparing the number of novel words produced in the three testing sessions, we found the groups to be equivalent, a finding we take to suggest that schizophrenic patients' lexicon is intact. Covarying current IQ eliminated the group difference robustly for letter fluency, while only marginally for semantic fluency. Our data revealed the presence of impairment in semantic and letter fluency tasks in schizophrenic patients consistent with previous reports, and also that patients were differentially impaired on semantic categories.     

Confabulation of denial in senile dementia. An experimental study.

Some forms of confabulation ('confabulation of denial') seem due to the need to deny demential dissolution by replacing information pointing to illness with expressions suggesting normal health and efficiency. Seventy-six unselected patients affected by senile dementia were investigated in order to study the relationships between confabulation of denial and (a) stage attained by the demential process; (b) degree of memory loss, and (c) personality features and cultural models of the patients. Confabulations of denial were absent in the initial and the most advanced stages of dementia, whereas they frequently occurred in the stages of state and of evolution of illness. Memory loss did not seem to be directly responsible of the symptom, while personality features and social cultural models seemed to have a definite valence in the development of confabulation of denial. Some implications of these findings are discussed.     

Relationships between medication treatments and neuropsychological test performance in schizophrenia.

Few investigations have assessed the neuropsychological effects of psychotropic medications on schizophrenic patients. In this study, 44 clinically stable schizophrenic inpatients were administered a battery of neuropsychological tests, and their performance was correlated with dosage of neuroleptic medication and benztropine. Neuroleptic dose was correlated with poorer performance on tests of psychomotor speed and attention, and with the number of perserverative errors on the Wisconsin Card Sort. Anticholinergic dose was associated with poorer verbal learning, verbal fluency, and motor speed. Both medication dosages were associated with poorer verbal recognition memory, but this association was strongly influenced by the performance of individuals on the highest medication doses. The findings, which were independent of clinical state and intelligence, indicate that higher doses of neuroleptic and anticholinergic medications are associated with poorer neuropsychological functioning in schizophrenia.     

Confabulation: motivated reality monitoring

The study addressed the hypothesis that the content of confabulation is emotionally biased. Confabulating amnesic patients were compared with amnesic non-confabulating patients in a memory recognition experiment that manipulated the valence (pleasant, unpleasant), temporal source (past, present, future) and selection agent (self, other) of the to-be-recognised memories. The results revealed that confabulating patients were more likely than amnesic non-confabulating patients to incorrectly recognise past autobiographical events or thoughts as currently relevant memories, and this was more pronounced for pleasant compared to unpleasant events. These findings suggest that motivational factors, along with defective reality and temporality monitoring, contribute to confabulation.     

The need to relate cognitive deficits to specific behavioral referents of schizophrenia

The implicit rationale for many cognitive studies of schizophrenia hinges on the recognition that verbal communication generated by patients with this disorder is often elusive or difficult to comprehend. This observation has led to the inference that a cognitive dysfunction, which mediates the production of discourse failure, is characteristic of schizophrenia. Unfortunately, most investigators have chosen to examine this type of hypothesis by comparing heterogeneous groups of schizophrenic patients (without regard to whether they exhibit verbal communication impairment) with various control samples; they have not studied the association between cognitive processes and specific schizophrenic symptoms. Data are presented from two studies indicating that such relationships, even when highly plausible, cannot simply be presumed. In both studies, one with adults suffering from schizophrenia and the other with children at risk, a laboratory measure of referential communication failed to be strongly related to language disorder. These data suggest that future investigators should specify the features of schizophrenia that are expected to correlate with their laboratory measures and empirically evaluate these relations.     

Clustering and switching strategies in verbal fluency tasks: comparison between schizophrenics and healthy adults.

Verbal fluency tasks are frequently used in clinical neuropsychology. Clustering (the production of words within semantic subcategories) and switching (the ability to shift between clusters) have been described as 2 components underlying fluency performance. We compared the use of clustering and switching in schizophrenic patients and healthy subjects. Seventy-eight schizophrenic subjects (DSM-IV criteria) and 64 control participants matched for age and educational level were recruited. Negative, disorganized, and productive clinical dimensions were evaluated using the SANS and SAPS scales. The number of words generated per semantic-phonemic cluster and the number of switches were evaluated during 2 verbal fluency tasks (phonemic and semantic). In the healthy controls switching and clustering were closely related to the total number of words generated in the verbal fluency tests. The role of the 2 components was partly dependent on the specific task. Switching was prevalent in formal fluency, while both switching and clustering contributed to semantic fluency. In comparison to the healthy controls, the overall group of schizophrenic patients showed a significant impairment of switching in the formal fluency task and of both switching and clustering in the semantic fluency task, and both the negative and disorganized dimensions correlated with verbal fluency performance, the number of swtiches during the phonemic fluency task, and the clustering during semantic fluency task.     

Verbal learning and memory in schizophrenic and Parkinson's disease patients

The purpose of this study was to investigate the neurofunctional substrate of verbal learning and memory impairments in schizophrenic patients. In this pilot study, our aim was to compare the memory disturbance of schizophrenic patients to the subcortico-frontal memory profile of Parkinson's disease (PD) patients. The California Verbal Learning Test, a verbal episodic memory test, was administered to 60 subjects, 20 patients with schizophrenia, 20 patients with PD and 20 healthy control subjects. All subjects were aged between 50 and 70 years and all patients were in a stable phase. Like the Parkinson patients, the schizophrenic patients showed a major deficit of retrieval characterized by deficit of recalls but contrarily to PD patients, schizophrenic patients' encoding scores were altered. These impairments in episodic memory could suggest a dysfunction of the subcortico-frontal circuits in schizophrenic patients. However, they demonstrated an additional encoding deficit associated with probable frontal in situ alteration.     

Learning and memory impairment in cocaine-dependent and comorbid schizophrenic patients

Impairments in verbal learning and memory functioning have been found to be cardinal features among individuals with schizophrenia as well as among non-schizophrenic cocaine abusers. Cognitive deficits in these areas, moreover, have been associated with poor treatment response and short-term outcome. Little is known, however, about the acute effects of cocaine abuse on schizophrenic patients' learning and memory functioning. Consequently, a potentially reversible and treatable source of cognitive impairment has been virtually ignored. The present study examined the extent of verbal learning and memory impairment in a group of cocaine-dependent schizophrenic patients (n=42) and a group of non-schizophrenic cocaine-dependent patients (n=21) within 72 h of the last cocaine use using the California Verbal Learning Test (CVLT). Schizophrenic patients (n=34) without any substance-use disorders were also tested in an identical time frame and served as a comparison group. Results revealed that all groups demonstrated significant learning and memory impairment relative to CVLT published age and gender corrected norms. Both cocaine-dependent and non-substance abusing schizophrenic groups presented a very similar pattern of impaired learning and recall performance across all CVLT task domains. Comorbid patients, in contrast, presented with marked deficits in their ability to learn and recall verbal information relative to either schizophrenic or cocaine-only groups. Moreover, the cocaine-abusing schizophrenic patients showed significant forgetfulness of the information that they did acquire during delayed recall conditions. The performance deficits exhibited by cocaine-abusing schizophrenic patients differed not only in relative severity of impairment, but also qualitatively in their increased rates of forgetfulness of acquired information. These results are interpreted in terms of the neurobiological substrates of learning and memory and the neurobiological impact of cocaine on schizophrenic patients' cognition during the early phase of inpatient hospitalization. These results suggest that comorbid patients should be targeted for specialized remediation efforts at the beginning phases of inpatient treatment.