User-Centered Development of STOP (Successful Treatment for Paranoia): Material Development and Usability Testing for a Digital Therapeutic for Paranoia

BACKGROUND

Paranoia is a highly debilitating mental health condition. One novel intervention for paranoia is cognitive bias modification for paranoia (CBM-pa). CBM-pa comes from a class of interventions that focus on manipulating interpretation bias. Here, we aimed to develop and evaluate new therapy content for CBM-pa for later use in a self-administered digital therapeutic for paranoia called STOP ("Successful Treatment of Paranoia").

OBJECTIVE

This study aimed to (1) take a user-centered approach with input from living experts, clinicians, and academics to create and evaluate paranoia-relevant item content to be used in STOP and (2) engage with living experts and the design team from a digital health care solutions company to cocreate and pilot-test the STOP mobile app prototype.

METHODS

We invited 18 people with living or lived experiences of paranoia to create text exemplars of personal, everyday emotionally ambiguous scenarios that could provoke paranoid thoughts. Researchers then adapted 240 suitable exemplars into corresponding intervention items in the format commonly used for CBM training and created 240 control items for the purpose of testing STOP. Each item included newly developed, visually enriching graphics content to increase the engagement and realism of the basic text scenarios. All items were then evaluated for their paranoia severity and readability by living experts (n=8) and clinicians (n=7) and for their item length by the research team. Items were evenly distributed into six 40-item sessions based on these evaluations. Finalized items were presented in the STOP mobile app, which was co-designed with a digital health care solutions company, living or lived experts, and the academic team; user acceptance was evaluated across 2 pilot tests involving living or lived experts.

RESULTS

All materials reached predefined acceptable thresholds on all rating criteria: paranoia severity (intervention items: ≥1; control items: ≤1, readability: ≥3, and length of the scenarios), and there was no systematic difference between the intervention and control group materials overall or between individual sessions within each group. For item graphics, we also found no systematic differences in users' ratings of complexity (P=.68), attractiveness (P=.15), and interest (P=.14) between intervention and control group materials. User acceptance testing of the mobile app found that it is easy to use and navigate, interactive, and helpful.

CONCLUSIONS

Material development for any new digital therapeutic requires an iterative and rigorous process of testing involving multiple contributing groups. Appropriate user-centered development can create user-friendly mobile health apps, which may improve face validity and have a greater chance of being engaging and acceptable to the target end users.

Cognitive bias modification for paranoia (CBM-pa): a randomised controlled feasibility study in patients with distressing paranoid beliefs

BACKGROUND

Cognitive Bias Modification for paranoia (CBM-pa) is a novel, theory-driven psychological intervention targeting the biased interpretation of emotional ambiguity associated with paranoia. Study objectives were (i) test the intervention's feasibility, (ii) provide effect size estimates, (iii) assess dose-response and (iv) select primary outcomes for future trials.

METHODS

In a double-blind randomised controlled trial, sixty-three outpatients with clinically significant paranoia were randomised to either CBM-pa or an active control (text reading) between April 2016 and September 2017. Patients received one 40 min session per week for 6 weeks. Assessments were given at baseline, after each interim session, post-treatment, and at 1- and 3-months post-treatment.

RESULTS

A total of 122 patients were screened and 63 were randomised. The recruitment rate was 51.2%, with few dropouts (four out of 63) and follow-up rates were 90.5% (1-month) and 93.7% (3-months). Each session took 30-40 min to complete. There was no statistical evidence of harmful effects of the intervention. Preliminary data were consistent with efficacy of CBM-pa over text-reading control: patients randomised to the intervention, compared to control patients, reported reduced interpretation bias (d = -0.48 to -0.76), improved symptoms of paranoia (d = -0.19 to -0.38), and lower depressed and anxious mood (d = -0.03 to -0.29). The intervention effect was evident after the third session.

CONCLUSIONS

CBM-pa is feasible for patients with paranoia. A fully powered randomised control trial is warranted.

Variability and magnitude of brain glutamate levels in schizophrenia: a meta and mega-analysis

Glutamatergic dysfunction is implicated in schizophrenia pathoaetiology, but this may vary in extent between patients. It is unclear whether inter-individual variability in glutamate is greater in schizophrenia than the general population. We conducted meta-analyses to assess (1) variability of glutamate measures in patients relative to controls (log coefficient of variation ratio: CVR); (2) standardised mean differences (SMD) using Hedges g; (3) modal distribution of individual-level glutamate data (Hartigan's unimodality dip test). MEDLINE and EMBASE databases were searched from inception to September 2022 for proton magnetic resonance spectroscopy (1H-MRS) studies reporting glutamate, glutamine or Glx in schizophrenia. 123 studies reporting on 8256 patients and 7532 controls were included. Compared with controls, patients demonstrated greater variability in glutamatergic metabolites in the medial frontal cortex (MFC, glutamate: CVR = 0.15, p < 0.001; glutamine: CVR = 0.15, p = 0.003; Glx: CVR = 0.11, p = 0.002), dorsolateral prefrontal cortex (glutamine: CVR = 0.14, p = 0.05; Glx: CVR = 0.25, p < 0.001) and thalamus (glutamate: CVR = 0.16, p = 0.008; Glx: CVR = 0.19, p = 0.008). Studies in younger, more symptomatic patients were associated with greater variability in the basal ganglia (BG glutamate with age: z = -0.03, p = 0.003, symptoms: z = 0.007, p = 0.02) and temporal lobe (glutamate with age: z = -0.03, p = 0.02), while studies with older, more symptomatic patients associated with greater variability in MFC (glutamate with age: z = 0.01, p = 0.02, glutamine with symptoms: z = 0.01, p = 0.02). For individual patient data, most studies showed a unimodal distribution of glutamatergic metabolites. Meta-analysis of mean differences found lower MFC glutamate (g = -0.15, p = 0.03), higher thalamic glutamine (g = 0.53, p < 0.001) and higher BG Glx in patients relative to controls (g = 0.28, p < 0.001). Proportion of males was negatively associated with MFC glutamate (z = -0.02, p < 0.001) and frontal white matter Glx (z = -0.03, p = 0.02) in patients relative to controls. Patient PANSS total score was positively associated with glutamate SMD in BG (z = 0.01, p = 0.01) and temporal lobe (z = 0.05, p = 0.008). Further research into the mechanisms underlying greater glutamatergic metabolite variability in schizophrenia and their clinical consequences may inform the identification of patient subgroups for future treatment strategies.

Alpha3/alpha2 power ratios relate to performance on a virtual reality shopping task in ageing adults

Background

Aspects of cognitive function decline with age. This phenomenon is referred to as age-related cognitive decline (ARCD). Improving the understanding of these changes that occur as part of the ageing process can serve to enhance the detection of the more incapacitating neurodegenerative disorders such as Alzheimer’s disease (AD). In this study, we employ novel methods to assess ARCD by exploring the utility of the alpha3/alpha2 electroencephalogram (EEG) power ratio – a marker of AD, and a novel virtual reality (VR) functional cognition task – VStore, in discriminating between young and ageing healthy adults.

Materials and methods

Twenty young individuals aged 20–30, and 20 older adults aged 60–70 took part in the study. Participants underwent resting-state EEG and completed VStore and the Cogstate Computerised Cognitive Battery. The difference in alpha3/alpha2 power ratios between the age groups was tested using t-test. In addition, the discriminatory accuracy of VStore and Cogstate were compared using logistic regression and overlying receiver operating characteristic (ROC) curves. Youden’s J statistic was used to establish the optimal threshold for sensitivity and specificity and model performance was evaluated with the DeLong’s test. Finally, alpha3/alpha2 power ratios were correlated with VStote and Cogstate performance.

Results

The difference in alpha3/alpha2 power ratios between age cohorts was not statistically significant. On the other hand, VStore discriminated between age groups with high sensitivity (94%) and specificity (95%) The Cogstate Pre-clinical Alzheimer’s Battery achieved a sensitivity of 89% and specificity of 60%, and Cogstate Composite Score achieved a sensitivity of 83% and specificity of 85%. The differences between the discriminatory accuracy of VStore and Cogstate models were statistically significant. Finally, high alpha3/alpha2 power ratios correlated strongly with VStore (r = 0.73), the Cogstate Pre-clinical Alzheimer’s Battery (r = -0.67), and Cogstate Composite Score (r = -0.76).

Conclusion

While we did not find evidence that the alpha3/alpha2 power ratio is elevated in healthy ageing individuals compared to young individuals, we demonstrated that VStore can classify age cohorts with high accuracy, supporting its utility in the assessment of ARCD. In addition, we found preliminary evidence that elevated alpha3/alpha2 power ratio may be linked to lower cognitive performance.

Interactive effects of task load and music tempo on psychological, psychophysiological, and behavioural outcomes during simulated driving

We examined the interactive effects of task load and music tempo on cognition, affect, cardiac response, and safety-relevant behaviour during simulated driving. Using a counterbalanced, within-subjects design, participants (N = 46) were exposed to fast-, slow-, and no-music conditions at high and low loads in a high-grade simulator. Task load had the most salient effect across a broad swath of variables. For core affect, the Load × Music Condition interaction showed that, under high load, affective arousal scores were higher in the fast-tempo condition vs. slow. A main effect of tempo emerged for the HRV index of SDNN, with fast-tempo music eliciting lower scores than both slow- and no-music conditions. Behavioural data showed a main effect of tempo for risk ratings, with fast-tempo music eliciting the highest scores for a traffic-light trigger. Our findings indicate that drivers in high-load, urban environments should exercise caution in their use of fast-tempo music. Practitioner summary: We examined the interactive effects of task load and music tempo in simulated driving (urban and highway). Cognition, mood, cardiac response, and driving behaviour were assessed. Participants exhibited more risky behaviours in response to fast-tempo music. Drivers should exercise caution in their use of up-tempo music in urban settings.

A Novel Virtual Reality Assessment of Functional Cognition: Validation Study

Background

Cognitive deficits are present in several neuropsychiatric disorders, including Alzheimer disease, schizophrenia, and depression. Assessments used to measure cognition in these disorders are time-consuming, burdensome, and have low ecological validity. To address these limitations, we developed a novel virtual reality shopping task—VStore.

Objective

This study aims to establish the construct validity of VStore in relation to the established computerized cognitive battery, Cogstate, and explore its sensitivity to age-related cognitive decline.

Methods

A total of 142 healthy volunteers aged 20-79 years participated in the study. The main VStore outcomes included verbal recall of 12 grocery items, time to collect items, time to select items on a self-checkout machine, time to make the payment, time to order coffee, and total completion time. Construct validity was examined through a series of backward elimination regression models to establish which Cogstate tasks, measuring attention, processing speed, verbal and visual learning, working memory, executive function, and paired associate learning, in addition to age and technological familiarity, best predicted VStore performance. In addition, 2 ridge regression and 2 logistic regression models supplemented with receiver operating characteristic curves were built, with VStore outcomes in the first model and Cogstate outcomes in the second model entered as predictors of age and age cohorts, respectively.

Results

Overall VStore performance, as indexed by the total time spent completing the task, was best explained by Cogstate tasks measuring attention, working memory, paired associate learning, and age and technological familiarity, accounting for 47% of the variance. In addition, with λ=5.16, the ridge regression model selected 5 parameters for VStore when predicting age (mean squared error 185.80, SE 19.34), and with λ=9.49 for Cogstate, the model selected all 8 tasks (mean squared error 226.80, SE 23.48). Finally, VStore was found to be highly sensitive (87%) and specific (91.7%) to age cohorts, with 94.6% of the area under the receiver operating characteristic curve.

Conclusions

Our findings suggest that VStore is a promising assessment that engages standard cognitive domains and is sensitive to age-related cognitive decline.

Psychological, psychophysiological and behavioural effects of participant-selected vs. researcher-selected music in simulated urban driving

We investigated the effect of participant-selected (PSel) and researcher-selected (RSel) music on urban driving behaviour in young men (N = 27; M_age = 20.6 years, SD = 1.9 years). A counterbalanced, within-subjects design was used with four simulated driving conditions: PSel fast-tempo music, PSel slow-tempo music, RSel music and an urban traffic-noise control. The between-subjects variable of personality (introverts vs. extroverts) was explored. The presence of PSel slow-tempo music and RSel music optimised affective valence and arousal for urban driving. NASA Task Load Index scores indicated that the urban traffic-noise control increased mental demand compared to PSel slow-tempo music. In the PSel slow-tempo condition, less use was made of the brake pedal. When compared to extroverts, introverts recorded lower mean speed and attracted lower risk ratings under PSel slow-tempo music. The utility of PSel slow-tempo and RSel music was demonstrated in terms of optimising affective state for simulated urban driving.

Cognitive control network connectivity differentially disrupted in treatment resistant schizophrenia

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Mechanisms underlying treatment-resistant schizophrenia are unclear.

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Effective connectivity within cortico-striatal network differentially disrupted in resistant patients.

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Resistance associated with lack of top-down control and aberrant glutamate function.

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We suggest a subtype of schizophrenia with distinct neurobiological mechanism.

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Results are important for guiding treatment strategies and developing new drugs.

Antipsychotic treatment resistance affects a third of people with schizophrenia and the underlying mechanism remains unclear. We used an fMRI emotion-yoked reward learning task, allied to prefrontal cortical glutamate levels, to explain the role of cognitive control in differentiating treatment-resistant from responsive patients. We investigated how reward learning is disrupted at the network level in 21 medicated treatment-responsive and 20 medicated treatment-resistant patients with schizophrenia compared with 24 healthy controls (HC). Dynamic Causal Modelling assessed how effective connectivity between regions in a cortico-striatal-limbic network is disrupted in each patient group compared to HC. Connectivity was also examined with respect to symptoms, salience and anterior cingulate (ACC) glutamate levels measured from the same region of the ACC. We found that ACC connectivity differentiated these patient groups, with responsive patients exhibiting increased top-down connectivity from ACC to sensory regions and reduced ACC drive to the striatum, while resistant patients showed altered connectivity within the ACC itself. In these resistant patients, the ACC drive to striatum was positively correlated with their symptom severity. ACC glutamate levels were found to correlate with ACC control over sensory regions in responsive patients but not in resistant patients. We suggest a central non-dopaminergic impairment that impacts cognitive control networks in treatment-resistant schizophrenia. This impairment was associated with disrupted reward learning and could be underpinned by aberrant glutamate function. These findings should form the focus of future treatment strategies (e.g. glutamatergic targets and giving clozapine earlier) in resistant patients.

Examination of the neural basis of psychotic-like experiences in adolescence during processing of emotional faces

Contemporary theories propose that dysregulation of emotional perception is involved in the aetiology of psychosis. 298 healthy adolescents were assessed at age 14- and 19-years using fMRI while performing a facial emotion task. Psychotic-like experiences (PLEs) were assessed with the CAPE-42 questionnaire at age 19. The high PLEs group at age 19 years exhibited an enhanced response in right insular cortex and decreased response in right prefrontal, right parahippocampal and left striatal regions; also, a gradient of decreasing response to emotional faces with age, from 14 to 19 years, in the right parahippocampal region and left insular cortical area. The right insula demonstrated an increasing response to emotional faces with increasing age in the low PLEs group, and a decreasing response over time in the high PLEs group. The change in parahippocampal/amygdala and insula responses during the perception of emotional faces in adolescents with high PLEs between the ages of 14 and 19 suggests a potential 'aberrant' neurodevelopmental trajectory for critical limbic areas. Our findings emphasize the role of the frontal and limbic areas in the aetiology of psychotic symptoms, in subjects without the illness phenotype and the confounds introduced by antipsychotic medication.

The neural mechanisms of social reward in early psychosis

In chronic psychosis, reduced trust is associated with a neural insensitivity to social reward and reduced theory of mind (ToM). Here we investigate whether these mechanisms could underlie emerging social impairments in early psychosis. Twenty-two participants with early psychosis and 25 controls (male, 13–19 years) participated in two interactive trust games against a cooperative and unfair partner. Region of interest neuroimaging analyses included right caudate, medial prefrontal cortex (mPFC) and right temporoparietal junction (rTPJ), involved in reward and ToM processing. Both groups showed similar levels of trust (i.e. investments). However, individuals with psychosis failed to activate the caudate differentially in response to cooperation and unfairness while making decisions to trust. During cooperative returns, patients showed reduced and controls increased caudate activation. Patients demonstrated greater rTPJ activation than controls, possibly pointing towards compensatory mechanisms. Effects were associated with Wechsler Abbreviated Scale of Intelligence vocabulary scores. No group differences emerged in mPFC activation. Early psychosis is associated with an aberrant neural sensitivity to social reward. This could foster reduced social motivation and social isolation. Absent behavioural differences in early, relative to chronic psychosis could indicate that trust is achieved through increased compensatory demand on ToM.

Neural correlates of positive and negative symptoms through the illness course: an fMRI study in early psychosis and chronic schizophrenia

Psychotic illness is associated with cognitive control deficits and abnormal recruitment of neural circuits subserving cognitive control. It is unclear to what extent this dysfunction underlies the development and/or maintenance of positive and negative symptoms typically observed in schizophrenia. In this study we compared fMRI activation on a standard Stroop task and its relationship with positive and negative symptoms in early psychosis (EP, N = 88) and chronic schizophrenia (CHR-SZ, N = 38) patients. CHR-SZ patients showed reduced frontal, striatal, and parietal activation across incongruent and congruent trials compared to EP patients. Higher positive symptom severity was associated with reduced activation across both trial types in supplementary motor area (SMA), middle temporal gyrus and cerebellum in EP, but not CHR-SZ patients. Higher negative symptom severity was associated with reduced cerebellar activation in EP, but not in CHR-SZ patients. A negative correlation between negative symptoms and activation in SMA and precentral gyrus was observed in EP patients and in CHR-SZ patients. The results suggest that the neural substrate of positive symptoms changes with illness chronicity, and that cognitive control related neural circuits may be most relevant in the initial development phase of positive symptoms. These findings also highlight a changing role for the cerebellum in the development and later maintenance of both positive and negative symptoms.

A qualitative study of the acceptability of cognitive bias modification for paranoia (CBM-pa) in patients with psychosis

BACKGROUND

Cognitive Bias Modification (CBM) has been used successfully as a computer-based intervention in disorders such as anxiety. However, CBM to modify interpretations of ambiguous information relevant to paranoia has not yet been tested. We conducted a qualitative investigation of a novel intervention called CBM for paranoia (CBM-pa) to examine its acceptability in patients with psychosis.

METHODS

Eight participants with psychosis who completed CBM-pa were identified by purposive sampling and invited for a semi-structured interview to explore the facilitators and barriers to participation, optimum form of delivery, perceived usefulness of CBM-pa and their opinions on applying CBM-pa as a computerised intervention. The interviews were transcribed and analysed using thematic analysis by researchers working in collaboration with service users.

RESULTS

Themes emerged relating to participants' perception about delivery, engagement, programme understanding, factors influencing experience, perceived impact and application of CBM-pa. CBM-pa was regarded as easy, straightforward and enjoyable. It was well-accepted among those we interviewed, who understood the procedure as a psychological intervention. Patients reported that it increased their capacity for adopting alternative interpretations of emotionally ambiguous scenarios. Although participants all agreed on the test-like nature of the current CBM-pa format, they considered that taking part in sessions had improved their overall wellbeing. Most of them valued the computer-based interface of CBM-pa but favoured the idea of combining CBM-pa with some form of human interaction.

CONCLUSIONS

CBM-pa is an acceptable intervention that was well-received by our sample of patients with paranoia. The current findings reflect positively on the acceptability and experience of CBM-pa in the target population. Patient opinion supports further development and testing of CBM-pa as a possible adjunct treatment for paranoia.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN: 90749868 . Retrospectively registered on 12 May 2016.

Mapping cortical surface features in treatment resistant schizophrenia with in vivo structural MRI

Decreases in cortical volume (CV), thickness (CT) and surface area (SA) have been reported in individuals with schizophrenia by in vivo MRI studies. However, there are few studies that examine these cortical measures as potential biomarkers of treatment resistance (TR) and treatment response (NTR) in schizophrenia. This study used structural MRI to examine differences in CV, CT, and SA in 42 adults with schizophrenia (TR = 21, NTR = 21) and 23 healthy controls (HC) to test the hypothesis that individuals with TR schizophrenia have significantly greater reductions in these cortical measures compared to individuals with NTR schizophrenia. We found that individuals with TR schizophrenia showed significant reductions in CV and CT compared to individuals with NTR schizophrenia in right frontal and precentral regions, right parietal and occipital cortex, left temporal cortex and bilateral cingulate cortex. In line with previous literature, the temporal lobe and cingulate gyrus in both patient groups showed significant reductions of all three measures when compared to healthy controls. Taken together these results suggest that regional changes in CV and CT may index mechanisms specific to TR schizophrenia and potentially identify patients with TR schizophrenia for earlier treatment.

Examination of the Neural Basis of Psychoticlike Experiences in Adolescence During Reward Processing

IMPORTANCE

Psychoticlike experiences (PLEs) are subclinical manifestations of psychotic symptoms and may reflect an increased vulnerability to psychotic disorders. Contemporary models of psychosis propose that dysfunctional reward processing is involved in the cause of these clinical illnesses.

OBJECTIVE

To examine the neuroimaging profile of healthy adolescents at 14 and 19 years old points with PLEs, using a reward task.

DESIGN, SETTING, AND PARTICIPANTS

A community-based cohort study, using both a cross-sectional and longitudinal design, was conducted in academic centers in London, Nottingham, United Kingdom, and Dublin, Ireland; Paris, France; and Berlin, Hamburg, Mannheim, and Dresden, Germany. A group of 1434 healthy adolescent volunteers was evaluated, and 2 subgroups were assessed at ages 14 and 19 years. Those who scored as either high or low PLE (based on the upper and lower deciles) on the Community Assessment of Psychic Experiences Questionnaire (CAPE-42) at age 19 years were included in the analysis. The study was conducted from January 1, 2016, to January 1, 2017.

MAIN OUTCOMES AND MEASURES

Participants were assessed at age 14 and 19 year points using functional magnetic resonance imaging while performing a monetary incentive delay reward task. A first-level model focused on 2 predefined contrasts of anticipation and feedback of a win. The second-level analysis examined activation within the reward network using an a priori-defined region of interest approach. The main effects of group, time, and their interaction on brain activation were examined.

RESULTS

Of the 1434 adolescents, 2 groups (n = 149 each) (high PLEs, n = 149, 50 [33.6%] male; low PLEs, n = 149, 84 [56.4%] male) were compared at ages 14 and 19 years. Two regions within the left and right middle frontal gyri showed a main effect of time on brain activation (F1, 93 = 5.559; P = .02; F1, 93 = 5.009; P = .03, respectively); there was no main effect of group. One region within the right middle frontal gyrus demonstrated a significant time × group interaction (F1, 93 = 7.448; P = .01).

CONCLUSION AND RELEVANCE

The findings are consistent with evidence implicating alterations in prefrontal and striatal function during reward processing in the etiology of psychosis. Given the nature of this nonclinical sample this may reflect a combination of aberrant salience yielding abnormal experiences and a compensatory cognitive control mechanism necessary to contextualize them.

Differential neural reward mechanisms in treatment-responsive and treatment-resistant schizophrenia

BACKGROUND

The significant proportion of schizophrenia patients refractory to treatment, primarily directed at the dopamine system, suggests that multiple mechanisms may underlie psychotic symptoms. Reinforcement learning tasks have been employed in schizophrenia to assess dopaminergic functioning and reward processing, but these have not directly compared groups of treatment-refractory and non-refractory patients.

METHODS

In the current functional magnetic resonance imaging study, 21 patients with treatment-resistant schizophrenia (TRS), 21 patients with non-treatment-resistant schizophrenia (NTR), and 24 healthy controls (HC) performed a probabilistic reinforcement learning task, utilizing emotionally valenced face stimuli which elicit a social bias toward happy faces. Behavior was characterized with a reinforcement learning model. Trial-wise reward prediction error (RPE)-related neural activation and the differential impact of emotional bias on these reward signals were compared between groups.

RESULTS

Patients showed impaired reinforcement learning relative to controls, while all groups demonstrated an emotional bias favoring happy faces. The pattern of RPE signaling was similar in the HC and TRS groups, whereas NTR patients showed significant attenuation of RPE-related activation in striatal, thalamic, precentral, parietal, and cerebellar regions. TRS patients, but not NTR patients, showed a positive relationship between emotional bias and RPE signal during negative feedback in bilateral thalamus and caudate.

CONCLUSION

TRS can be dissociated from NTR on the basis of a different neural mechanism underlying reinforcement learning. The data support the hypothesis that a favorable response to antipsychotic treatment is contingent on dopaminergic dysfunction, characterized by aberrant RPE signaling, whereas treatment resistance may be characterized by an abnormality of a non-dopaminergic mechanism - a glutamatergic mechanism would be a possible candidate.

Salience attribution and its relationship to cannabis-induced psychotic symptoms

BACKGROUND

Cannabis is a widely used drug associated with increased risk for psychosis. The dopamine hypothesis of psychosis postulates that altered salience processing leads to psychosis. We therefore tested the hypothesis that cannabis users exhibit aberrant salience and explored the relationship between aberrant salience and dopamine synthesis capacity.

METHOD

We tested 17 cannabis users and 17 age- and sex-matched non-user controls using the Salience Attribution Test, a probabilistic reward-learning task. Within users, cannabis-induced psychotic symptoms were measured with the Psychotomimetic States Inventory. Dopamine synthesis capacity, indexed as the influx rate constant K i cer , was measured in 10 users and six controls with 3,4-dihydroxy-6-[18F]fluoro-l-phenylalanine positron emission tomography.

RESULTS

There was no significant difference in aberrant salience between the groups [F 1,32 = 1.12, p = 0.30 (implicit); F 1,32 = 1.09, p = 0.30 (explicit)]. Within users there was a significant positive relationship between cannabis-induced psychotic symptom severity and explicit aberrant salience scores (r = 0.61, p = 0.04) and there was a significant association between cannabis dependency/abuse status and high implicit aberrant salience scores (F 1,15 = 5.8, p = 0.03). Within controls, implicit aberrant salience was inversely correlated with whole striatal dopamine synthesis capacity (r = -0.91, p = 0.01), whereas this relationship was non-significant within users (difference between correlations: Z = -2.05, p = 0.04).

CONCLUSIONS

Aberrant salience is positively associated with cannabis-induced psychotic symptom severity, but is not seen in cannabis users overall. This is consistent with the hypothesis that the link between cannabis use and psychosis involves alterations in salience processing. Longitudinal studies are needed to determine whether these cognitive abnormalities are pre-existing or caused by long-term cannabis use.

Brain-imaging studies of treatment-resistant schizophrenia: a systematic review

Around 30% of patients with schizophrenia show an inadequate response to antipsychotics-ie, treatment resistance. Neuroimaging studies can help to uncover the underlying neurobiological reasons for such resistance and identify these patients earlier. Additionally, studies examining the effect of clozapine on the brain can help to identify aspects of clozapine that make it uniquely effective in patients with treatment resistance. We did a systematic search of PubMed between Jan 1, 1980, and April 13, 2015, to identify all neuroimaging studies that examined treatment-resistant patients or longitudinally assessed the effects of clozapine treatment. We identified 330 articles, of which 61 met the inclusion criteria. Replicated differences between treatment-resistant and treatment-responsive patients include reductions in grey matter and perfusion of frontotemporal regions, and increases in white matter and basal ganglia perfusion, with effect sizes ranging from 0·4 to greater than 1. Clozapine treatment led to reductions in caudate nucleus volume in three separate studies. The available evidence supports the hypothesis that some of the neurobiological changes seen in treatment-resistant schizophrenia lie along a continuum with treatment-responsive schizophrenia, whereas other differences are categorical in nature and have potential to be used as biomarkers. However, further replication is needed, and for neuroimaging findings to be clinically translatable, future studies need to focus on a-priori hypotheses and be adequately powered.

Treatment-Resistant Schizophrenia Patients Show Elevated Anterior Cingulate Cortex Glutamate Compared to Treatment-Responsive

INTRODUCTION

Resistance to antipsychotic treatment is a significant clinical problem in patients with schizophrenia with approximately 1 in 3 showing limited or no response to repeated treatments with antipsychotic medication. The neurobiological basis for treatment resistance is unknown but recent evidence implicates glutamatergic function in the anterior cingulate cortex. We examined glutamate levels of chronically ill treatment-resistant patients directly compared to treatment-responsive patients.

METHODS

We acquired proton magnetic resonance spectroscopy (1H-MRS) at 3 Tesla from 21 treatment-resistant and 20 treatment-responsive patients. All participants had a DSM-IV diagnosis of schizophrenia. Treatment-resistant patients were classified using the modified Kane criteria. The groups were matched for age, sex, smoking status, and illness duration.

RESULTS

Glutamate to creatine ratio levels were higher in treatment-resistant patients (Mean [SD] = 1.57 [0.24]) than in treatment-responsive patients (Mean[SD] = 1.38 [0.23]), (T[35] = 2.34, P = .025, 2-tailed), with a large effect size of d = 0.76. A model assuming 2 populations showed a 25% improvement in the fit of the Akaike weights (0.55) over a model assuming 1 population (0.44), producing group values almost identical to actual group means.

DISCUSSION

Increased anterior cingulate glutamate level is associated with treatment-resistant schizophrenia. This appears to be a stable neurobiological trait of treatment-resistant patients. We discuss possible explanations for glutamatergic dysfunction playing a significant role in resistance to conventional antipsychotic treatments, which are all dopamine-2 receptor blockers. Our findings suggest that glutamatergic treatments may be particularly effective in resistant patients and that 1H-MRS glutamate indices can potentially have clinical use.

Presynaptic Serotoninergic Regulation of Emotional Processing: A Multimodal Brain Imaging Study

BACKGROUND

The amygdala is a central node in the brain network that processes aversive emotions and is extensively innervated by dorsal raphe nucleus (DRN) serotonin (5-hydroxytryptamine [5-HT]) neurons. Alterations in DRN 5-HT1A receptor availability cause phenotypes characterized by fearful behavior in preclinical models. However, it is unknown whether 5-HT1A receptor availability is linked specifically to the processing of aversive emotions in humans or whether it modulates connectivity in brain networks involved in emotion processing. To answer this question, we investigated the relationship between DRN 5-HT1A receptor availability and amygdala reactivity to aversive emotion and functional connectivity within the amygdala-cortical network.

METHODS

We studied 15 healthy human participants who underwent positron emission tomography scanning with [(11)C]CUMI-101, a 5-HT1A partial agonist radioligand, and functional magnetic resonance imaging of brain responses during an incidental emotion processing task including happy, fearful, and neutral faces. Regional estimates of 5-HT1A receptor binding potential (nondisplaceable) were obtained by calculating total volumes of distribution for presynaptic DRN and amygdala. Connectivity between the amygdala and corticolimbic areas was assessed using psychophysiologic interaction analysis with the amygdala as the seed region.

RESULTS

Analysis of the fear versus neutral contrast revealed a significant negative correlation between amygdala response and DRN binding potential (nondisplaceable) (r = -.87, p < .001). Availability of DRN 5-HT1A receptors positively correlated with amygdala connectivity with middle frontal gyrus, anterior cingulate cortex, bilateral precuneus, and left supramarginal gyrus for fearful (relative to neutral) faces.

CONCLUSIONS

Our data show that DRN 5-HT1A receptor availability is linked specifically to the processing of aversive emotions in the amygdala and the modulation of amygdala-cortical connectivity.

Attentional Control and Suppressing Negative Thought Intrusions in Pathological Worry

Adaptive behavior relies on the ability to effectively and efficiently ignore irrelevant information, an important component of attentional control. The current research found that fundamental difficulties in ignoring irrelevant material are related to dispositional differences in trait propensity to worry, suggesting a core deficit in attentional control in high worriers. The degree of deficit in attentional control correlated with the degree of difficulty in suppressing negative thought intrusions in a worry assessment task. A cognitive training procedure utilizing a flanker task was used in an attempt to improve attentional control. Although the cognitive training was largely ineffective, improvements in attentional control were associated with improvements in the ability to suppress worry-related thought intrusions. Across two studies, the findings indicate that the inability to control worry-related negative thought intrusions is associated with a general deficiency in attentional control.

Dopamine function in cigarette smokers: an [¹⁸F]-DOPA PET study

Tobacco addiction is a global public health problem. Addiction to tobacco is thought to involve the effects of nicotine on the dopaminergic system. Only one study has previously investigated dopamine synthesis capacity in cigarette smokers. This study, exclusively in male volunteers, reported increased dopamine synthesis capacity in heavy smokers compared with non-smokers. We sought to determine whether dopamine synthesis capacity was elevated in a larger sample of cigarette smokers that included females. Dopamine synthesis capacity was measured in 15 daily moderate smokers with 15 sex- and age-matched control subjects who had never smoked tobacco. Dopamine synthesis capacity (indexed as the influx rate constant K(i)(cer)) was measured with positron emission tomography and 3,4-dihydroxy-6-[(18)F]-fluoro-l-phenylalanine. There was no significant group difference in dopamine synthesis capacity between smokers and non-smoker controls in the whole striatum (t28=0.64, p=0.53) or any of its functional subdivisions. In smokers, there were no significant relationships between the number of cigarettes smoked per day and dopamine synthesis capacity in the whole striatum (r=-0.23, p=0.41) or any striatal subdivision. These findings indicate that moderate smoking is not associated with altered striatal dopamine synthesis capacity.

MEG and EEG data fusion: simultaneous localisation of face-evoked responses

We present an empirical Bayesian scheme for distributed multimodal inversion of electromagnetic forward models of EEG and MEG signals. We used a generative model with common source activity and separate error components for each modality. Under this scheme, the weightings of error for each modality, relative to source components, are estimated automatically from the data, by optimising the model-evidence. This obviates the need for arbitrary user-defined weightings. To evaluate the scheme, we acquired three types of data simultaneously from twelve participants: total magnetic flux (as recorded by 102 magnetometers), orthogonal in-plane gradients of the magnetic field (as recorded by 204 planar gradiometers) and voltage differences in the electrical field (recorded by 70 electrodes). We assessed the relative precision of each sensor-type in terms of signal-to-noise ratio (SNR); using empirical sample variances and optimised estimators from the generative model. We then compared the localisation of face-evoked responses, using each modality separately, with that obtained by their "fusion" under the common generative model. Finally, we quantified the conditional precisions of the source estimates using their posterior covariance, confirming that EEG can improve MEG-based source reconstructions.

Electrophysiological correlates of masked face priming

Using a sandwich-masked priming paradigm with faces, we report two ERP effects that appear to reflect different levels of subliminal face processing. These two ERP repetition effects dissociate in their onset, scalp topography, and sensitivity to face familiarity. The "early" effect occurred between 100 and 150 ms, was maximally negative-going over lateral temporoparietal channels, and was found for both familiar and unfamiliar faces. The "late" effect occurred between 300 and 500 ms, was maximally positive-going over centroparietal channels, and was found only for familiar faces. The early effect resembled our previous fMRI data from the same paradigm; the late effect resembled the behavioural priming found, in the form of faster reaction times to make fame judgments about primed relative to unprimed familiar faces. None of the ERP or behavioural effects appeared explicable by a measure of participants' ability to see the primes. The ERP and behavioural effects showed some sensitivity to whether the same or a different photograph of a face was repeated, but could remain reliable across different photographs, and did not appear attributable to a low-level measure of pixelwise overlap between prime and probe photograph. The functional significance of these ERP effects is discussed in relation to unconscious perception and face processing.

The detection of fear-relevant stimuli: are guns noticed as quickly as snakes?

Potentially dangerous stimuli are important contenders for the capture of visual-spatial attention, and it has been suggested that an evolved fear module is preferentially activated by stimuli that are fear relevant in a phylogenetic sense (e.g., snakes, spiders, angry faces). In this study, a visual search task was used to test this hypothesis by directly contrasting phylogenetically (snakes) and ontogenetically (guns) fear-relevant stimuli. Results showed that the modern threat was detected as efficiently as the more ancient threat. Thus, both guns and snakes attracted attention more effectively than neutral stimuli (flowers, mushrooms, and toasters). These results support a threat superiority effect but not one that is preferentially accessed by threat-related stimuli of phylogenetic origin. The results are consistent with the view that faster detection of threat in visual search tasks may be more accurately characterized as relevance superiority effects rather than as threat superiority effects.