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Biomedical subjects

Johanna C Badcock

Publications and source records attributed to Johanna C Badcock.

12 recordsLinked to original sources
PubMed2007

On keeping (intrusive) thoughts to one's self: testing a cognitive model of auditory hallucinations.

BACKGROUND: Previous studies have linked intrusive cognitions (hallucinations and obsessions) with inhibitory dysregulation. Combined deficits in intentional inhibition and context memory have been proposed to explain the intrusive nature and perceived nonself origin of auditory hallucinations (Waters et al., 2006). This study tested the prediction, from this model, that individuals with obsessive-compulsive disorder (OCD), who do not mistake the origin of their intrusive thoughts, will show a deficit of intentional inhibition but intact contextual memory. METHOD: The performance of 14 individuals with OCD and 24 healthy controls was compared on two measures of intentional cognitive inhibition and on a context memory task.Results. Participants with OCD were significantly impaired on both measures of inhibition but were not significantly different from controls in any condition of the context memory task. CONCLUSIONS: The predictions were confirmed. Individuals with OCD, like schizophrenia patients with auditory hallucinations, showed impaired intentional inhibition. This impairment might be responsible for the intrusive thoughts reported in both disorders, and might also partially account for the high rates of comorbidity of OCD and schizophrenia. Finally, intact context memory abilities in OCD may contribute to an efficient memory system, and may differentiate this group from those with hallucinations.

Adult↗
PubMed2006

Selective attention for negative information and depression in schizophrenia.

OBJECTIVES: Depression is a frequent feature of schizophrenia but the cognitive processes involved in its development and maintenance are unclear. Recent studies have shown that clinical depression is associated with faulty inhibitory mechanisms of selective attention for negative information. The current study examined whether patients with schizophrenia also have an attentional bias towards negative stimuli. The inhibitory processes of interference control and task-shifting abilities were also examined to assess whether patients would show a selective impairment. METHOD: Forty-three patients with schizophrenia and 24 healthy controls completed the Affective Shifting Task. RESULTS: As a group, schizophrenia patients did not show an attentional bias for negative material. However, those patients with high levels of depression demonstrated faster latencies when negative words were the targets, and higher depression scores were found to be associated with an increasing number of false alarms for negative words when they were not the targets. The results also showed that patients had impaired interference control but intact task-shifting abilities. CONCLUSIONS: Faulty inhibitory mechanisms of selective attention for negative information are not a general feature of schizophrenia but appear to be selective to those with a depressed mood. The results highlight the need for further studies examining the exact nature of the affective dysfunction in schizophrenia and the cognitive processes supporting negative emotions.

Adult↗
PubMed2006

Validity and consistency of self-reports regarding substance use in general research volunteers, including regular cannabis users and schizophrenia patients.

This study investigated the validity of self-reports of substance use in 69 low-level substance users from the general community of Perth, Australia, volunteering for electrophysiological research, between 2002 and 2003. The participants included regular cannabis users and schizophrenia patients. Self-reports of recent use (last 24 hours) highly agreed with urine screen results (kappa = 0.91). Self-reports of past use (lifetime and last 12 months) had poor-moderate consistency based on correlations among dependence (measured with SDS, FTND, SMAST, CAGE), frequency, and use duration. Therefore, under some conditions, self-reports are valid for recent use and only moderately consistent for past substance use in general research participants.

Adolescent↗
PubMed2006

Auditory hallucinations in schizophrenia: intrusive thoughts and forgotten memories.

INTRODUCTION: This paper presents a new cognitive model of auditory hallucinations in schizophrenia. We suggest that auditory hallucinations are auditory representations derived from the unintentional activation of memories and other irrelevant current mental associations. Our model proposes that a combination of deficits in intentional inhibition and contextual memory is critical to the experience of auditory hallucinations. The failure in intentional inhibition produces unwanted and uncontrollable mental events which are not recognised because they have lost the contextual cues that would normally facilitate recognition. METHODS: This article amalgamates recently published data and presents a reanalysis of the findings on 43 patients with a diagnosis of schizophrenia (Badcock, Waters, Maybery, & Michie, 2005; Waters, Badcock, Maybery, & Michie, 2003a; Waters, Maybery, Badcock, & Michie, 2004a). Relative risk was also estimated to determine whether the combination of deficits increases the risk of having auditory hallucinations. RESULTS: Almost 90% of patients currently experiencing auditory hallucinations showed the predicted combination of deficits on both inhibition and context memory, compared to only a third of patients without hallucinations. In addition, the results showed that those patients with the specified cognitive deficits were at an especially increased risk of having auditory hallucinations relative to patients without the deficits. CONCLUSIONS: The results of our investigations strongly support the role of intentional inhibition and context memory in auditory hallucinations. Critical consideration of the findings also suggests that additional cognitive processes might be important for the expression of this symptom.

Cognition↗
PubMed2005

Dimensions of intelligence in schizophrenia: evidence from patients with preserved, deteriorated and compromised intellect.

There is a growing literature describing a subgroup of "high-functioning" people with schizophrenia who show preserved intellectual ability (IQ). A detailed characterisation of the cognitive abilities of this group may be important in targeting appropriate treatment, management and services for patients with schizophrenia. It is a widely held belief that variation in cognitive processing speed is the basis of individual differences in intelligence. The main objective of this study was to identify subgroups of schizophrenia patients with preserved (N=45), deteriorated (N=47) and compromised (N=17) intellect in order to study whether these subgroups differ in specific cognitive abilities (e.g. executive functions) or in general cognitive processing speed, as measured with an inspection time (IT) task. The patients who displayed an average estimated premorbid IQ, with no evidence of IQ decline (premorbid-current IQ difference <10 points), were found to show better performance on measures of executive function (continuous performance task, verbal fluency) compared with patients in the deteriorated and compromised subgroups. Nevertheless, this represented significantly impaired performance relative to healthy controls. In contrast, the average inspection times of patients with preserved IQ were as slow as those obtained in the deteriorated or compromised groups, indicating that high functioning patients are impaired in terms of cognitive processing speed. Furthermore, the average IT for all schizophrenia groups was significantly slower than that of healthy controls. These findings suggest that high functioning patients with schizophrenia exhibit enduring cognitive difficulties that may impact on their ability to benefit from rehabilitation interventions.

Adolescent↗
PubMed2005

Spatial working memory and planning ability: contrasts between schizophrenia and bipolar I disorder.

Working memory may be conceptualized as a multi-component system involving the active maintenance and manipulation of stored information in the service of planning/guiding behaviour. Impaired spatial working memory is a robust finding in schizophrenia patients which has been related to an impairment in frontostriatal connectivity. The purpose of this study was to examine the specificity of this impairment by comparing the mnemonic and executive aspects of working memory performance in schizophrenia and bipolar disorder with psychotic features, focusing particularly on the functional dynamics between task components. Twenty-four patients with schizophrenia, 14 patients with bipolar I disorder (manic phase) and 33 healthy control subjects were assessed using the Cambridge Neuropsychological Test Automated Battery (CANTAB): including the spatial working memory (between search errors and strategy scores) spatial span (storage capacity) and spatial planning (Stockings of Cambridge: accuracy and latency) tasks. Both patient groups were impaired on the spatial span task, which requires the maintenance and retrieval of stored information. In contrast, only schizophrenia patients showed a significant deficit in between search errors, which requires both maintenance and manipulation of information in working memory. That is, they exhibited both a mnemonic and an executive dysfunction. Spatial span was particularly important to accurate planning ability in bipolar patients. In contrast, in patients with schizophrenia poor spatial working memory was a significant predictor of planning impairments, consistent with failures in goal selection, evaluation and/or execution. Furthermore, initial planning time was positively correlated with the latency to complete a planning sequence. This pattern of slow cognitive processing in schizophrenia patients only, resembled that reported previously in patients with basal ganglia disorders. These findings are discussed in terms of a possible common disturbance in fronto-parietal circuitry in the two disorders together with a specific disturbance of fronto-striatal circuitry in schizophrenia, that is not present in bipolar disorder.

Adult↗
PubMed2005

Auditory hallucinations: failure to inhibit irrelevant memories.

INTRODUCTION: The frequency of auditory hallucinations (AH) is associated with efficiency in inhibiting irrelevant memories, suggesting that the presence of AH may be related to the intrusion of strongly activated representations in memory. Therefore, we hypothesised that the inability to suppress irrelevant memories would be found only in patients currently experiencing AH. METHOD: Performance on a repeated, continuous recognition task was examined in 23 schizophrenia patients with AH present, 20 schizophrenia patients with AH absent, and 24 healthy controls. RESULTS: Patients with current AH made significantly more inappropriate responses (false alarms) to distractors seen on previous runs of the task than nonhallucinating patients. The ability to detect targets (hits) was significantly better in healthy controls than schizophrenia patients, however, there was no significant difference between the two patient subgroups. CONCLUSIONS: The findings confirm that the presence of AH involves a failure to suppress memories that are not relevant to ongoing reality. We propose that a combination of deficits in inhibition and (episodic) memory provides a useful model of AH, which can accommodate many of the characteristic features of the symptom and fits well with the neuroanatomical circuitry that is believed to underlie the occurrence of AH.

Journal Article↗
PubMed2005

Laterality phenotypes in patients with schizophrenia, their siblings and controls: associations with clinical and cognitive variables.

BACKGROUND: Various behavioural indices of brain lateralisation significantly intercorrelate, but current research in this area still focuses on single behavioural asymmetries, such as handedness. AIMS: To describe a novel approach, which simultaneously integrates various laterality indices and delineates complex phenotypes. METHOD: Grade of membership analysis was used to describe latent, complex lateralisation phenotypes in patients with schizophrenia (n=157), their siblings (n=74) and controls (n=77). The indices used were asymmetries of eye, foot and hand; hand motor proficiency; and handedness of patient's first-degree relatives. RESULTS: Three distinct pure types of lateralisation ('right', 'left' and 'mixed') were evident in patients compared with two ('right' and 'left') in siblings and controls. The 'mixed' type in patients featured absence of eye and foot lateralisation and presence of familial sinistrality, despite a right-hand dominance for writing. Patients with schizophrenia expressing the 'left' phenotype had a more severe course of illness, significantly increased scores on two schizotypy factors and poorer neurocognitive performance. The pure types in the siblings were similar to those in healthy controls. CONCLUSIONS: The findings suggest that a leftward reversal, rather than a reduction in lateralisation, is associated with clinical severity and neurocognitive deficits in patients with schizophrenia.

Adolescent↗
PubMed2004

Context memory and binding in schizophrenia.

The current study aimed to provide evidence for the context-memory hypothesis, which proposes that schizophrenia is linked to a deficit in retrieving contextual information and in binding the different components of a memory together. A new task was developed in which memory for the content of events could be assessed in conjunction with memory for both source and temporal information. Forty-three patients with schizophrenia and 24 normal controls took part in the study. Patients were found to be less accurate in identifying the source and temporal context of events. Furthermore, whereas controls tended to identify correctly both source and temporal context of events, patients tended to have a more fractionated recollection of those events. The study provides support for the context-memory hypothesis by demonstrating that patients with schizophrenia show a fundamental deficit in binding contextual cues together to form a coherent representation of an event in memory.

Adult↗
PubMed2004

Speed of processing and individual differences in IQ in schizophrenia: General or specific cognitive deficits?

INTRODUCTION: The aim of this study was to re-examine the role of cognitive processing speed in the vulnerability to schizophrenia, using an inspection time (IT) task that does not require a speeded manual response. Since IT consistently correlates with intelligence, the relationship between IT and general intelligence was also explored. METHODS: Patients with schizophrenia were compared with unaffected siblings of schizophrenia patients and healthy controls on a visual IT task. Both speed and variability of IT performance were examined. Current intellectual ability (IQ) was estimated with the Shipley Institute of Living Scale (SILS), which yields separate assessments of verbal and abstraction abilities. RESULTS: Schizophrenia patients produced ITs that were significantly slower and more variable than either unaffected siblings or healthy controls. These results are not related to demographic or clinical variables. A significant negative correlation was obtained between IT and IQ; specifically, longer IT values were associated with abstraction scores only. CONCLUSIONS: These findings confirm that basic cognitive processing efficiency is impaired in patients with schizophrenia. In contrast, ITs in unaffected siblings did not differ from healthy controls, in line with their better IQ test scores. Implications for models of general and specific heritable dimensions in schizophrenia are discussed.

Journal Article↗
PubMed2003

Inhibition in schizophrenia: association with auditory hallucinations.

The study investigated whether auditory hallucinations (AH) in schizophrenia are linked to a deficit in inhibition. Two tasks assessing the intentional suppression of cognitive events-the Hayling Sentence Completion Test (HSCT) [Neuropsychologia 34 (1996) 263] and the Inhibition of Currently Irrelevant Memories Task (ICIM) [Nature Neuroscience 2 (1999) 677]-were administered to 42 patients with schizophrenia and 24 normal controls. Presence and severity of symptoms in the patient group were examined using the Positive and Negative Syndrome Scale (PANSS). Patients performed significantly worse on the measures of inhibition compared to controls. More importantly, among patients, significant positive correlations were obtained between an index of AH severity (defined as an increase in frequency of AH on PANSS) and the number of type A errors on the HSCT and errors in the last three runs of the ICIM. An increase in AH severity was, therefore, associated with increasingly impaired control of intentional inhibition. Furthermore, no significant correlations were found between these indices of inhibition and either negative, general or positive symptoms (excluding AH scores).

Adult↗