Jennifer C. Whitman

The Contribution of a Cognitive Bias Against Disconfirmatory Evidence (BADE) to Delusions in Schizophrenia

A neuropsychological paradigm is introduced that provides a measure of a bias against disconfirmatory evidence (BADE), and its correspondence with delusions in people with schizophrenia and schizoaffective disorder was investigated. Fifty-two patients diagnosed with schizophrenia or schizoaffective disorder (36 were acutely delusional) and 24 healthy control participants were presented with delusion-neutral pictures in each trial, and were asked to rate the plausibility of four written interpretations of the scenario depicted by that picture. Subsequently, new pictures that provided background information about the depicted scenario were successively presented, and participants were requested to adjust their ratings, taking into account this new information. Two of the interpretations appeared tenable initially but ultimately proved to be implausible, one appeared untenable initially but eventually proved to be plausible, and one appeared untenable at all stages. A BADE was observed for delusional compared to non-delusional patients, as well as for all patients compared to controls. In addition, regardless of symptom profile, patients were more accepting of implausible interpretations than controls. The present work suggests that deficits in reasoning may contribute to the maintenance of delusions via an impairment in the processing of disconfirmatory evidence. The authors thank Jessica Bristowe, Jannine Laseleta, and Tonya Kragelj for assistance with data collection and data management, and Drs. Karin Christensen, Mahesh Menon, Elton Ngan, Eric Strachan, and Ivan Torres for comments and discussions that shaped this work. This research was supported by post-doctoral fellowships from the Mind Foundation of BC, the Canadian Psychiatric Research Foundation, and the Canadian Institutes of Health Research to TSW, scholarships from the German Academic Exchange Program (DAAD) to SM, and a grant from the Riverview Hospital Academic Steering Committee to TSW.

Confidence in Errors as a Possible Basis for Delusions in Schizophrenia

In two previous studies, it was observed that schizophrenic patients display increased confidence in memory errors compared with controls. The patient group displayed an increased proportion of errors in their knowledge system, quantified as the percentage of high-confident responses that are errors. The latter phenomenon has been termed knowledge corruption and is put forward as a risk factor for the emergence of delusions. In the present study, knowledge corruption was analyzed separately for different aspects of memory errors. A source-monitoring task was used, for which participants (30 schizophrenic patients with past or current paranoid ideas and 15 healthy controls) were asked to provide associates for each of 20 prime words. Later, participants were required to recognize studied words among distractor words, judge the original source, and provide a confidence rating for the most recent decision. Schizophrenic patients displayed greater confidence in memory errors compared with controls. Knowledge corruption was observed to be significantly greater in schizophrenic patients relative to controls for false-positive and false-negative judgments. It is proposed that reliance on false knowledge represents a candidate mechanism for the emergence of fixed false beliefs (i.e., delusions).

False Memories in Schizophrenia.

In prior studies, it was observed that patients with schizophrenia show abnormally high knowledge corruption (i.e., high-confident errors expressed as a percentage of all high-confident responses were increased for schizophrenic patients relative to controls). The authors examined the conditions under which excessive knowledge corruption occurred using the Deese-Roediger-McDermott paradigm. Whereas knowledge corruption in schizophrenia was significantly greater for false-negative errors relative to controls, no group difference occurred for false-positive errors. The groups showed a comparable high degree of confidence for false-positive recognition of critical lure items. Similar to findings collected in elderly participants, patients, but not controls, showed a strong positive correlation between the number of recognized studied items and false-positive recognition of the critical lure.

Decreased Efficiency of Task-Positive and Task-Negative Networks During Working Memory in Schizophrenia

Working memory (WM) is one of the most impaired cognitive processes in schizophrenia. Functional magnetic resonance imaging (fMRI) studies in this area have typically found a reduction in information processing efficiency but have focused on the dorsolateral prefrontal cortex. In the current study using the Sternberg Item Recognition Test, we consider networks of regions supporting WM and measure the activation of functionally connected neural networks over different WM load conditions. We used constrained principal component analysis with a finite impulse response basis set to compare the estimated hemodynamic response associated with different WM load condition for 15 healthy control subjects and 15 schizophrenia patients. Three components emerged, reflecting activated (task-positive) and deactivated (task-negative or default-mode) neural networks. Two of the components (with both task-positive and task-negative aspects) were load dependent, were involved in encoding and delay phases (one exclusively encoding and the other both encoding and delay), and both showed evidence for decreased efficiency in patients. The results suggest that WM capacity is reached sooner for schizophrenia patients as the overt levels of WM load increase, to the point that further increases in overt memory load do not increase fMRI activation, and lead to performance impairments. These results are consistent with an account holding that patients show reduced efficiency in task-positive and task-negative networks during WM and also partially support the shifted inverted-U-shaped curve theory of the relationship between WM load and fMRI activation in schizophrenia.

Source monitoring biases and auditory hallucinations

Introduction. Previous source monitoring studies on schizophrenia reported an association between external source misattribution and hallucinations, but this is often not replicated. This inconsistency may be attributable to a failure in accounting for guessing parameters when computing source monitoring biases. Methods. Fifty-one patients and 20 healthy controls were required to recall the source of items originating from external (computer and experimenter) or internal (the subject) sources. When statistically determined criteria were met, the appropriate counts of false positives were entered as covariates in the statistical analyses (analysis of covariance; ANCOVA) to exclude guessing from source monitoring bias measures. Results. When comparing patients to controls, impairments on item recognition and source discrimination were observed. When comparing patient groups split on hallucinations, a bias towards attributing self-generated items to an external source was observed. A group difference on the externalisation bias was absent when the sample was split on delusions. Conclusions. A bias towards attributing self-generated items to an external source was associated with hallucinations. This ANCOVA methodology is recommended for source monitoring studies investigating group differences, and suggests that previously reported null results may be attributable to a failure in separating guessing and source monitoring measures.

Action and outcome activity state patterns in the anterior cingulate cortex.

Although there are numerous theories regarding anterior cingulate cortex (ACC) function, most suggest that it is involved in some form of action or outcome processing. The present study characterized the dominant patterns of ACC activity on a task in which actions and outcomes could vary independently. Patterns of activity were detected using a modified form of principal component analysis (PCA), termed constrained PCA in which a regression procedure was applied prior to PCA to eliminate the contribution of nontask-related activity. When trials were grouped according to outcome, a PC was found in all subjects and sessions that had large fluctuations during actions but only differentiated correct versus error trials prior to the end of the delay and again at time of the outcome. Another PC was always present that separated right from left lever presses, but only around the time of the actual lever press. Individual neurons exhibited significant selectivities for trials involving different actions and/or outcomes. Of the ACC neurons that exhibited significant outcome selectivity, the majority fired more on error trials. The present study revealed separate as well as integrated action and outcome monitoring in the ACC, especially, although not exclusively, under conditions when an error is likely.

Inhibition of return in the covert deployment of attention: Evidence from human electrophysiology

People are slow to react to objects that appear at recently attended locations. This delay—known as inhibition of return (IOR)—is believed to aid search of the visual environment by discouraging inspection of recently inspected objects. However, after two decades of research, there is no evidence that IOR reflects an inhibition in the covert deployment of attention. Here, observers participated in a modified visual-search task that enabled us to measure IOR and an ERP component called the posterior contralateral N2 (N2pc) that reflects the covert deployment of attention. The N2pc was smaller when a target appeared at a recently attended location than when it appeared at a recently unattended location. This reduction was due to modulation of neural processing in the visual cortex and the right parietal lobe. Importantly, there was no evidence for a delay in the N2pc. We conclude that in our task, the inhibitory processes underlying IOR reduce the probability of shifting attention to recently attended locations but do not delay the covert deployment of attention itself.

The bivalency effect in task switching: event-related potentials.

During task switching, if we occasionally encounter stimuli that cue more than one task (i.e., bivalent stimuli), response slowing is observed on all univalent trials within that block, even when no features overlap with the bivalent stimuli. This observation is known as the bivalency effect. Previous fMRI work (Woodward et al., 2008 ) clearly suggests a role for the dorsal anterior cingulate cortex (dACC) in the bivalency effect, but the time course remains uncertain. Here, we present the first high‐temporal resolution account for the bivalency effect using stimulus‐locked event‐related potentials. Participants alternated among three simple tasks in six experimental blocks, with bivalent stimuli appearing occasionally in bivalent blocks (blocks 2, 4, and 6). The increased reaction times for univalent stimuli in bivalent blocks demonstrate that these stimuli are being processed differently from univalent stimuli in purely univalent blocks. Frontal electrode sites captured significant amplitude differences associated with the bivalency effect within time windows 100–120 ms, 375–450 ms, and 500–550 ms, which may reflect additional extraction of visual features present in bivalent stimuli (100–120 ms) and suppression of processing carried over from irrelevant cues (375–450 ms and 500–550 ms). Our results support the fMRI findings and provide additional evidence for involvement of the dACC. Furthermore, the bivalency effect dissipated with extended practice both behaviorally and electrophysiologically. These findings are discussed in relation to the differential processing involved in a controlled response style. Hum Brain Mapp, 2013.

Left-Dominant Temporal-Frontal Hypercoupling in Schizophrenia Patients With Hallucinations During Speech Perception

BACKGROUND Task-based functional neuroimaging studies of schizophrenia have not yet replicated the increased coordinated hyperactivity in speech-related brain regions that is reported with symptom-capture and resting-state studies of hallucinations. This may be due to suboptimal selection of cognitive tasks. METHODS In the current study, we used a task that allowed experimental manipulation of control over verbal material and compared brain activity between 23 schizophrenia patients (10 hallucinators, 13 nonhallucinators), 22 psychiatric (bipolar), and 27 healthy controls. Two conditions were presented, one involving inner verbal thought (in which control over verbal material was required) and another involving speech perception (SP; in which control verbal material was not required). RESULTS A functional connectivity analysis resulted in a left-dominant temporal-frontal network that included speech-related auditory and motor regions and showed hypercoupling in past-week hallucinating schizophrenia patients (relative to nonhallucinating patients) during SP only. CONCLUSIONS These findings replicate our previous work showing generalized speech-related functional network hypercoupling in schizophrenia during inner verbal thought and SP, but extend them by suggesting that hypercoupling is related to past-week hallucination severity scores during SP only, when control over verbal material is not required. This result opens the possibility that practicing control over inner verbal thought processes may decrease the likelihood or severity of hallucinations.

Patterns of Cortical Oscillations Organize Neural Activity into Whole-Brain Functional Networks Evident in the fMRI BOLD Signal.

Recent findings from electrophysiology and multimodal neuroimaging have elucidated the relationship between patterns of cortical oscillations evident in EEG/MEG and the functional brain networks evident in the BOLD signal. Much of the existing literature emphasized how high-frequency cortical oscillations are thought to coordinate neural activity locally, while low-frequency oscillations play a role in coordinating activity between more distant brain regions. However, the assignment of different frequencies to different spatial scales is an oversimplification. A more informative approach is to explore the arrangements by which these low- and high-frequency oscillations work in concert, coordinating neural activity into whole-brain functional networks. When relating such networks to the BOLD signal, we must consider how the patterns of cortical oscillations change at the same speed as cognitive states, which often last less than a second. Consequently, the slower BOLD signal may often reflect the summed neural activity of several transient network configurations. This temporal mismatch can be circumvented if we use spatial maps to assess correspondence between oscillatory networks and BOLD networks.