Source-monitoring deficits for self-generated stimuli in schizophrenia: multinomial modeling of data from three sources

Impaired verbal source monitoring in schizophrenia: an intermediate trait vulnerability marker?

Patients with schizophrenia, particularly those with positive symptoms show impaired verbal source monitoring. Specific cognitive deficits have been observed during both active and remission phases of the illness as well as in groups of unaffected first degree relatives of patients with schizophrenia. This type of schizophrenia vulnerability marker may precede the onset of frank psychotic symptoms and contribute to their developments. The aim of this study was first to determine if unaffected siblings were impaired in discriminate internal vs. external generated events when compared to their remitted schizophrenics relatives and healthy subjects. Performances of healthy subjects were then compared with results from previous studies with acute hallucinating patients, acute non-hallucinating patients and patients with resistant auditory verbal hallucinations. Compared with healthy subjects, unaffected siblings are impaired (effect size, ES=0.7), remitted or acute non-hallucinating patients are more impaired than siblings (ES=1.4); patients with verbal auditory hallucinations (acute or resistant) are even more impaired than non-hallucinating patients (ES=2.1). Our results suggest that a source monitoring deficit could be considered as an intermediate vulnerability marker of schizophrenia.

Associative memory encoding and recognition in schizophrenia: an event-related fMRI study

BACKGROUND

We used an event-related functional Magnetic Resonance Imaging (fMRI) approach to examine the neural basis of the selective associative memory deficit in schizophrenia.

METHODS

Fifteen people with schizophrenia and 18 controls were scanned during a pair and item memory encoding and recognition task. During encoding, subjects studied items and pairs of visual objects. In a subsequent retrieval task, participants performed an item recognition memory test (old/new decisions) and an associative recognition test (intact/rearranged decisions). The fMRI analysis of the recognition data was restricted to correct items only and a random effects model was used.

RESULTS

At the behavioral level, both groups performed equally well on item recognition, whereas people with schizophrenia demonstrated lower performance on associative recognition relative to the control group. At the brain level, the comparison between associative and item encoding revealed greater activity in the control group in the left prefrontal cortex and cingulate gyrus relative to the schizophrenia group. During recognition, greater left dorsolateral prefrontal and right inferior prefrontal activations were observed in the control group relative to the schizophrenia group.

CONCLUSION

This fMRI study implicates the prefrontal cortex among other brain regions as the basis for the selective associative memory encoding and recognition deficit seen in schizophrenia.

The perceptual characteristics of voice-hallucinations in deaf people: insights into the nature of subvocal thought and sensory feedback loops

The study of voice-hallucinations in deaf individuals, who exploit the visuomotor rather than auditory modality for communication, provides rare insight into the relationship between sensory experience and how "voices" are perceived. Relatively little is known about the perceptual characteristics of voice-hallucinations in congenitally deaf people who use lip-reading or sign language as their preferred means of communication. The existing literature on hallucinations in deaf people is reviewed, alongside consideration of how such phenomena may fit into explanatory subvocal articulation hypotheses proposed for auditory verbal hallucinations in hearing people. It is suggested that a failure in subvocal articulation processes may account for voice-hallucinations in both hearing and deaf people but that the distinct way in which hallucinations are experienced may be due to differences in a sensory feedback component, which is influenced by both auditory deprivation and language modality. This article highlights how the study of deaf people may inform wider understanding of auditory verbal hallucinations and subvocal processes generally.

Functional magnetic resonance imaging of internal source monitoring in schizophrenia: recognition with and without recollection

Patients with schizophrenia tend to have impaired source monitoring and intact item recognition, suggesting an over-reliance of familiarity effects. We previously demonstrated that providing patients with a levels-of-processing (LOP) semantic encoding strategy normalized source monitoring. The current blood-oxygen-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) study tests the hypothesis that patients will have abnormally increased fronto-temporal activation despite intact performance. fMRI was measured in 13 patients and 13 demographically matched healthy controls during a LOP source monitoring paradigm. SPM2 was used for standard pre-processing and statistical analyses, with a corrected significance threshold of p<.05. Examination of accuracy and speed measures did not reveal any group differences in task performance. Regardless of source retrieval success both groups activated expected prefrontal and parietal regions, with no areas of relatively greater control versus patient activation. In support of the hypothesis, patients showed abnormally increased activation in temporolimbic areas including middle and superior temporal gyrus, thalamus, and parahippocampal gyrus. Activation in these areas was associated with worse positive and negative symptoms, but did not correlate with performance, suggesting inefficient rather than compensatory activation.

A neuropsychiatric model of biological and psychological processes in the remission of delusions and auditory hallucinations

This selective review combines cognitive models and biological models of psychosis into a tentative integrated neuropsychiatric model. The aim of the model is to understand better, how pharmacotherapy and cognitive-behavior therapy come forward as partners in the treatment of psychosis and play complementary and mutually reinforcing roles. The article reviews the dominant models in literature. The focus in this review is on one hand on neural circuits that are involved in cognitive models and on the other hand on cognitive processes and experiences involved in biological models. In this way, a 4-component neuropsychiatric model is tentatively constructed: (1) a biological component that leads to aberrant perceptions and salience of stimuli, (2) a cognitive component that attempts to explain the psychic abnormal events, (3) a mediating component with psychological biases which influences the reasoning process in the direction of the formation of (secondary) delusions, and (4) a component of psychological processes that maintains delusions and prevents the falsification of delusional ideas. Remission consists actually of 2 processes. Biological remission consists of the dampening of mesolimbic dopamine releases with antipsychotic medication and decreases the continuous salient experiences. Psychological remission consists of the reappraisal of primary psychotic experiences. Both forms of remission are partially independent. We expect that a full remission including biological and psychological remission could prevent relapse.

A First Step Toward Cognitive Remediation of Voices: a Case Study

Several studies have shown that source-monitoring errors are related to verbal hallucinations in schizophrenia. An exploratory pilot study has been carried out to investigate the possibility of training patients in how to avoid errors in source-monitoring. One patient with paranoid schizophrenia and persistent thought insertions was trained for 6 hours to use mnemonic techniques to compensate specific deficits in source-monitoring. Results show that the patient was able to improve his performance and maintain the acquired progress at a 1-month follow-up assessment. These preliminary results are interesting for developing a larger controlled study of cognitive remediation of source-monitoring deficits.

Discriminating imagined from perceived information engages brain areas implicated in schizophrenia

Some of the symptoms of schizophrenia may reflect a difficulty discriminating between information that was perceived from the outside world and information that was imagined. This study used fMRI to examine the brain regions associated with this reality monitoring ability in healthy volunteers, who recollected whether information had previously been perceived or imagined, or whether information had been presented on the left or right of a monitor screen. Recent studies have suggested that schizophrenia may be associated particularly with dysfunction in medial anterior prefrontal cortex, thalamus, and cerebellum. In our data, activation in all three of these regions of interest was significantly greater during recollection of whether stimuli had been perceived or imagined versus recollection of stimulus position. In addition, reduced prefrontal activation was associated with the same misattribution error that has been observed in schizophrenia. These results indicate a possible link between the brain areas implicated in schizophrenia and the regions supporting the ability to discriminate between perceived and imagined information.

Levels-of-processing effect on internal source monitoring in schizophrenia

BACKGROUND

Recognition can be normalized in schizophrenia by providing patients with semantic organizational strategies through a levels-of-processing (LOP) framework. However, patients may rely primarily on familiarity effects, making recognition less sensitive than source monitoring to the strength of the episodic memory trace. The current study investigates whether providing semantic organizational strategies can also normalize patients' internal source-monitoring performance.

METHOD

Sixteen clinically stable medicated patients with schizophrenia and 15 demographically matched healthy controls were asked to identify the source of remembered words following an LOP-encoding paradigm in which they alternated between processing words on a 'shallow' perceptual versus a 'deep' semantic level. A multinomial analysis provided orthogonal measures of item recognition and source discrimination, and bootstrapping generated variance to allow for parametric analyses. LOP and group effects were tested by contrasting recognition and source-monitoring parameters for words that had been encoded during deep versus shallow processing conditions.

RESULTS

As in a previous study there were no group differences in LOP effects on recognition performance, with patients and controls benefiting equally from deep versus shallow processing. Although there were no group differences in internal source monitoring, only controls had significantly better performance for words processed during the deep encoding condition. Patient performance did not correlate with clinical symptoms or medication dose.

CONCLUSIONS

Providing a deep processing semantic encoding strategy significantly improved patients' recognition performance only. The lack of a significant LOP effect on internal source monitoring in patients may reflect subtle problems in the relational binding of semantic information that are independent of strategic memory processes.

The effects of a subpsychotic dose of ketamine on recognition and source memory for agency: implications for pharmacological modelling of core symptoms of schizophrenia

Ketamine is increasingly used to model the cognitive deficits and symptoms of schizophrenia. We investigated the extent to which ketamine administration in healthy volunteers reproduces the deficits in episodic recognition memory and agency source monitoring reported in schizophrenia. Intravenous infusions of placebo or 100 ng/ml ketamine were administered to 12 healthy volunteers in a double-blind, placebo-controlled, randomized, within-subjects study. In response to presented words, the subject or experimenter performed a deep or shallow encoding task, providing a 2(drug) x 2(depth of processing) x 2(agency) factorial design. At test, subjects discriminated old/new words, and recalled the sources (task and agent). Data were analyzed using multinomial modelling to identify item recognition, source memory for agency and task, and guessing biases. Under ketamine, item recognition and cued recall of deeply encoded items were impaired, replicating previous findings. In contrast to schizophrenia, there was a reduced tendency to externalize agency source guessing biases under ketamine. While the recognition memory deficit observed with ketamine is consistent with previous work and with schizophrenia, the changes in source memory differ from those reported in schizophrenic patients. This difference may account for the pattern of psychopathology induced by ketamine.

Low frequency repetitive transcranial magnetic stimulation improves source monitoring deficit in hallucinating patients with schizophrenia

Auditory hallucinations have been associated with a disruption in monitoring one's own speech suggesting an autonoetic agnosia in schizophrenia. This deficit can be measured by a source monitoring task. Low frequency transcranial magnetic stimulations (rTMS) applied to the left temporoparietal cortex can inhibit cortical areas involved both in autonoetic agnosia (which means 'the inability to identify self-generated mental events') and in auditory hallucinations (AH) phenomena. Although improvements in AH have been repeatedly reported following rTMS treatment, effects on autonoetic agnosia measured by source monitoring have never been investigated. We aimed to investigate the relation between improvements in AH and source monitoring performance after rTMS treatment. Twenty four right-handed refractory schizophrenic patients with hallucinations randomly received sham or active 10.0001-Hz rTMS to the left temporoparietal cortex and performed 2 source monitoring tasks requiring discrimination between silent- and overt-reading words before and after rTMS sessions. Compared to sham, active rTMS significantly improved AH. Source monitoring performances and the improvements tended to correlate, which would support a specific relation between autonoetic agnosia and auditory hallucinations.

Increased hindsight bias in schizophrenia

An underlying theme common to prominent theoretical accounts of cognition in schizophrenia is that information processing is disproportionately influenced by recently/currently encountered information relative to the influence of previously learned information. In this study, the authors tested this account by using the hindsight bias or knew-it-all-along (KIA) paradigm, which demonstrates that newly acquired knowledge influences recall of past events. In line with the account that patients with schizophrenia display a disproportionately strong influence of recently encountered information relative to the influence of previously learned information, patients displayed a KIA effect that was significantly greater than in controls. This result is discussed in the context of the cognitive underpinnings of the KIA effect and delusion formation.

The contribution of metamemory deficits to schizophrenia

A number of recent studies have demonstrated that individuals with schizophrenia display knowledge corruption; that is, they hold false information with strong conviction. This aberration in metamemory is thought to stem from poor memory accuracy in conjunction with impaired discrimination of correct and incorrect judgments in terms of confidence. Thirty-one participants with schizophrenia, along with 61 healthy control participants and 48 control participants with other psychiatric conditions, participated in a computerized source memory task. Whereas no differences in memory accuracy were observed between the group with schizophrenia and the group with other psychiatric diagnoses, knowledge corruption was specifically impaired in those with schizophrenia. Schizophrenia participants showed a significantly decreased confidence gap: They were more confident in errors and less confident in correct responses relative to those in the control groups. Knowledge corruption is theorized to be a potential risk factor for the emergence of delusions.

Associative interference does not affect recognition memory in schizophrenia

Studies of schizophrenia suggest a specific impairment in binding different parts of a memory event into a cohesive whole, a finding that may account for the reported preferential deficits in associative recognition memory relative to item recognition. As a further test of this hypothesis and to exert greater control over task differences, we used a recognition memory interference test in which participants encoded landscape pictures that had each been divided into three segments. During encoding, subjects were presented with one segment from each of the landscapes. Then, an interference generating task followed consisting of the presentation of the second segment from half of the landscapes. Finally, a forced-choice recognition memory test consisted of the presentation of each encoding picture stimulus concurrently with the related third segment that had never been presented before. Thus, for half of the stimuli, additional related information was encoded and this is known to interfere with recognition memory. However, an impaired ability to bind this related information should reduce the interfering effect of associated stimuli. Thirty-five schizophrenia patients and 37 healthy controls were administered this memory interference task. A significant interaction between groups and recognition conditions was found with a significant interference effect observed for controls (performance dropping from 76% to 62%) but not for patients (performance remaining unchanged from 66% to 68%). These results provide further support for faulty associative memory processing in schizophrenia.

Impairment of specific episodic memory processes by sub-psychotic doses of ketamine: the effects of levels of processing at encoding and of the subsequent retrieval task

RATIONALE

The precise nature of the impact of the N-methyl-D-aspartate antagonist, ketamine, upon human episodic memory, has yet to be elucidated fully.

OBJECTIVES

This study sought to assess the effects of ketamine on the sub-processes facilitating memory encoding and retrieval.

METHODS

We evaluated the effects of the drug on a series of memory performance measures depending upon whether it was administered at the encoding or retrieval stage and on the nature of the encoding task used. Twelve healthy volunteers participated in a double-blind, placebo-controlled, randomized, within-subjects study. Intravenous infusions of placebo, 50 ng/ml ketamine or 100 ng/ml ketamine were administered. We investigated the effects of ketamine on three key aspects of episodic memory: encoding vs retrieval processes, source memory, and depth of processing. Data were analysed using both multinomial modelling and standard measures of item discrimination and response bias.

RESULTS

Deleterious effects of ketamine on episodic memory were primarily attributable to its effects on encoding, rather than retrieval processes. Recognition memory was impaired for items encoded at an intermediate level of processing, but preserved for shallowly and deeply encoded items. Increased source guessing bias was also observed when encoding took place under ketamine.

CONCLUSIONS

The effects of ketamine upon episodic memory seem, therefore, to predominate at encoding. Furthermore, our results are also consistent with a specific impairment of encoding processes that result in subsequent recollective, as opposed to familiarity-based, retrieval. The observed effects are compatible with memory deficits seen in schizophrenia and thus provide some support for the ketamine model of the disease.

A source-monitoring account of auditory verbal hallucinations in patients with schizophrenia

Auditory verbal hallucinations are a common and distressing symptom experienced by patients with schizophrenia. They can be understood as arising from an impairment in reality monitoring-the process by which internally and externally generated events are distinguished. This impairment might arise through primary abnormalities in the reality-monitoring mechanism or through secondary mechanisms (abnormalities in the perceptual characteristics of internally generated events or in the perception of externally generated events). This article examines evidence for and against an association between abnormalities in reality monitoring and auditory verbal hallucinations in schizophrenia. A comprehensive review of the psychological literature suggests that there is little evidence for an association between auditory verbal hallucinations and secondary mechanisms leading to abnormalities in reality monitoring. There is some evidence suggesting that hallucinators show a primary reality-monitoring abnormality that is most apparent when patients are required to distinguish self from other in real time. To draw firmer conclusions, however, it is imperative that future studies select patient populations precisely, match control groups, and use consistent criteria for defining hallucinators.

Cognition in schizophrenia: impairments, determinants, and functional importance

Recent findings support and add to earlier findings of cognitive dysfunction in schizophrenia. Deficits across neurocognitive domains such as attention, working memory, language skills, and executive functioning tend to be moderate, with the most pronounced deficits found in verbal learning and memory. All these neurocognitive domains are related to adaptive and social skills, with executive functions and verbal learning and memory showing more variance across more domains than other neuro-cognitive variables. Negative symptoms and neurocognitive domains, although correlated, are distinct and have differential pathways of change with treatment. General psychopathology symptoms, such as depression and anxiety, may become important treatment targets as strategies are developed for translating cognitive enhancement to real-world functional performance.

The effect of cognitive behavioral treatment on the positive symptoms of schizophrenia spectrum disorders: a meta-analysis

BACKGROUND

Despite the effectiveness of anti-psychotic pharmacotherapy, residual hallucinations and delusions do not completely resolve in some medicated patients. Additional cognitive behavioral therapy (CBT) seems to improve the management of positive symptoms. Despite promising results, the efficacy of CBT is still unclear. The present study addresses this issue taking into account a number of newly published controlled studies.

METHOD

Fourteen studies including 1484 patients, published between 1990 and 2004 were identified and a meta-analysis of their results performed.

RESULTS

Compared to other adjunctive measures, CBT showed significant reduction in positive symptoms and there was a higher benefit of CBT for patients suffering an acute psychotic episode versus the chronic condition (effect size of 0.57 vs. 0.27).

DISCUSSION

CBT is a promising adjunctive treatment for positive symptoms in schizophrenia spectrum disorders. However, a number of potentially modifying variables have not yet been examined, such as therapeutic alliance and neuropsychological deficits.

Cognitive and clinical moderators of recognition memory in schizophrenia: a meta-analysis

Recognition memory performance in schizophrenia has been shown to vary greatly across studies. To identify the conditions under which recognition memory is significantly impaired, we used a meta-analytic strategy to quantify the moderating effects of several cognitive and clinical variables. Eighty-four studies (from 1965 to July 2003) provided recognition memory data for both a schizophrenia and control group. The overall group comparison for recognition memory yielded a significant mean weighted effect size of d=0.76. Material specificity was the most significant cognitive variable found, with patients exhibiting greater impairment for figural than verbal recognition. A yes-no recognition format and auditory encoding also led to significantly greater effect sizes for recognition memory relative to forced-choice recognition tests and visual encoding, respectively. Furthermore, the effect size for recognition memory as measured by false alarm was smaller than the effect size as measured by hit rate or by d-prime and its related measures. Among clinical variables that were associated with higher effect sizes, chronicity was the most significant, but different trends linking poor performance to negative symptoms and general symptomatology were also observed. Thus, a recognition memory deficit moderated by both cognitive and clinical variables is clearly present in schizophrenia.

Factorial structure of the hallucinatory experience: continuity of experience in psychotic and normal individuals

Examination of the distribution of the hallucinatory experience may aide in the determination of their continuity and the psychological mechanisms that mediate their occurrence. Past investigators have found that hallucinatory experiences are not limited to disordered individuals and can be induced in the laboratory and occur naturally in the general population. Few reports to date, however, have directly investigated the continuity of the experience by comparing hallucinatory behavior of psychotic patients with a nonclinical sample. In the present study, we examined the architecture of the hallucinatory experience by comparing the factorial structure of the Launay-Slade Hallucination Scale using psychotic patients with active hallucinations, psychotic inpatients without hallucinations, and a group of university students. In support of the continuum model of psychosis, a very similar factor-analytic solution was obtained for all three groups. Discriminant function analysis, however, revealed that all groups achieved a high classified rate by their item responses. These results are consistent with the notion that expression of hallucinatory behavior exists along a continuum, but at a certain level of symptom severity beyond a critical threshold, the behavior becomes discontinuous and dysfunctional.

The cognitive neuropsychiatry of auditory verbal hallucinations: an overview

INTRODUCTION

The cognitive neuropsychiatric approach to auditory verbal hallucinations (AVHs) attempts to explain the phenomena in cognitive or information-processing terms and ultimately their brain bases.

METHODS

A narrative review of the literature and an overview of this special issue of Cognitive Neuropsychiatry.

RESULTS

First, an operational definition of AVHs is offered. Next, clues to etiology are derived from a detailed consideration of the clinical phenomenology of "voices", their form and content. Functional and structural neuroimaging studies suggest the importance of left-side language areas in the generation/perception of AVHs.

CONCLUSIONS

Existing cognitive neuropsychiatric models provide a useful framework for the understanding of AVHs. However, data need to be applied more specifically to these models so that they may be refined.

Habitual prospective memory in schizophrenia

BACKGROUND

Prospective memory (PM), the act of remembering that something has to be done in the future without any explicit prompting to recall, provides a useful framework with which to examine problems in internal-source monitoring. This is because it requires distinguishing between two internally-generated processes, namely the intention to perform an action versus actual performance of the action. In habitual tasks, such as taking medicine every few hours, the same PM task is performed regularly and thus it is essential that the individual is able to distinguish thoughts (i.e., thinking about taking the medicine) from actions (i.e., actually taking the medicine).

METHODS

We assessed habitual PM in patients with schizophrenia by employing a laboratory analogue of a habitual PM task in which, concurrently with maneuvering a ball around an obstacle course (ongoing activity), participants were to turn over a counter once during each trial (PM task). After each trial, participants were asked whether they had remembered to turn the counter over.

RESULTS

Patients with schizophrenia made a disproportionate number of errors compared to controls of reporting that a PM response had been made (i.e., the counter turned over) after an omission error (i.e., the counter was not turned over). There was no group difference in terms of reporting that an omission error occurred (i.e., forgetting to turn over the counter) when in fact a PM response had been made.

CONCLUSION

Patients with schizophrenia displayed a specific deficit distinguishing between two internally-generated sources, attributable to either poor source monitoring or temporal discrimination.