Insights to the schizophrenia continuum: A systematic review of saccadic eye movements in schizotypy and biological relatives of schizophrenia patients

The Future-oriented Repetitive Thought (FoRT) scale: Validation in Chinese samples and application in the schizophrenia spectrum

BACKGROUND

Repetitive thoughts are usually associated with psychopathology. The Future-oriented Repetitive Thought (FoRT) Scale is a measure designed to capture frequency of repetitive thought about positive and negative future events. However, the validity of the scale in Chinese population and its application in the schizophrenia spectrum have not been examined.

METHODS

The current study aimed to examine the psychometric properties of the Chinese version of the FoRT scale and to apply it to the schizophrenia spectrum. In Study 1, three samples (total N = 1875) of university students were recruited for exploratory factor analysis, confirmatory factor analysis, and validity test, respectively. In Study 2, we identified subsamples with high schizotypal traits (N = 89) and low schizotypal traits (N = 89), and recruited 36 inpatients with schizophrenia and 41 matched healthy controls.

RESULTS

The three-factor (pessimistic repetitive future thinking, repetitive thinking about future goals, and positive indulging about the future) structure of the FoRT scale with one item deleted, fitted the Chinese samples. And the scale could distinguish patients with schizophrenia and individuals with high schizotypal traits from controls.

CONCLUSION

These findings support that the Chinese version of the FoRT scale is a valid tool and provide evidence for the potential applications in the schizophrenia spectrum.

A Pilot Study to Improve Cognitive Performance and Pupil Responses in Mild Cognitive Impaired Patients Using Gaze-Controlled Gaming

Mild cognitive impairment (MCI) may progress to severe forms of dementia, so therapy is needed to maintain cognitive abilities. The neural circuitry for oculomotor control is closely linked to that which controls cognitive behavior. In this study, we tested whether training the oculomotor system with gaze-controlled video games could improve cognitive behavior in MCI patients. Patients played a simple game for 2-3 weeks while a control group played the same game using a mouse. Cognitive improvement was assessed using the MoCA screening test and CANTAB. We also measured eye pupil and vergence responses in an oddball paradigm. The results showed an increased score on the MoCA test specifically for the visuospatial domain and on the Rapid Visual Information Processing test of the CANTAB battery. Pupil responses also increased to target stimuli. Patients in the control group did not show significant improvements. This pilot study provides evidence for the potential cognitive benefits of gaze-controlled gaming in MCI patients.

Antisaccade error rates in first-episode psychosis, ultra-high risk for psychosis and unaffected relatives of schizophrenia: A systematic review and meta-analysis

BACKGROUND

Antisaccade, which is described as looking at the opposite location of the target, is an eye movements paradigm used for assessing cognitive functions in schizophrenia. Initiation and sustainment of saccades in antisaccade are managed by frontal and parietal cortical areas. Antisaccade abnormalities are well-established findings in schizophrenia. However, studies in the early phases of psychotic disorders and clinical/familial risk for psychosis reported inconsistent findings. The current systematic review aimed to review the results of studies investigating antisaccade error rates in first-episode psychosis (FEP), individuals with ultra-high-risk for psychosis (UHRP), and familial-high-risk for psychosis (FHRP) compared to healthy controls.

METHOD

A meta-analysis of 17 studies was conducted to quantitatively review antisaccade errors in FEP, UHR-P and FHRP. The error rate (Hedges'g) was compared between the total of 860 FEP, UHRP, FHRP, and 817 healthy controls. Hedges' g for effect size, I2 for estimating the percentage of variability, and publication bias were evaluated through the R software.

RESULTS

The outcomes of this meta-analysis suggested that FEP is associated with a robust deficit in the antisaccade error rate (g = 1.16, CI = 0.95-1.38). Additionally, both the clinical and familial high-risk groups showed small but significant increases in AS errors (g = 0.26, CI = 0.02-0.52 and g = 0.34, CI = 0.13-0.55, respectively).

CONCLUSION

The large effect size estimated for FEP was compatible with previously reported results in chronic schizophrenia patients. Additionally, relatives had abnormalities with small to medium effect sizes and significant differences. The current findings suggest that antisaccade errors might be a potential endophenotype for psychotic disorders.

Sleep spindle activity and psychotic experiences: Examining the mediating roles of attentional performance and perceptual distortions in a daytime nap study

Decreased sleep spindle activity in individuals with psychotic disorders is well studied, but its contribution to psychotic symptom formation is not well understood. This study explored potential underlying mechanisms explaining the association between decreased sleep spindle activity and psychotic symptoms. To this end, we analysed the links between sleep spindle activity and psychotic experiences and probed for the mediating roles of attentional performance and perceptual distortions in a community sample of young adults (N = 70; 26.33 ± 4.84 years). Polysomnography was recorded during a 90-min daytime nap and duration, amplitude, and density from slow (10-13 Hz) and fast (13-16 Hz) spindles were extracted. Attentional performance was assessed via a test battery and with an antisaccadic eye movement task. Psychotic experiences (i.e., paranoid thoughts; hallucinatory experiences) and perceptual distortions (i.e., anomalous perceptions; sensory gating deficits) were assessed via self-report questionnaires. We conducted sequential mediation analyses with spindle activity as predictor, psychotic experiences as dependent variable, and attentional performance and perceptual distortions as mediators. We found reduced right central spindle amplitude to be associated with paranoid thoughts. Increased antisaccadic error rate was associated with anomalous perceptions and perceptual distortions were associated with psychotic experiences. We did not find significant mediation effects. The findings support the notion that reduced sleep spindle activity is involved in the formation of paranoid thoughts and that decreased antisaccadic performance is indicative of perceptual distortions as potential precursors for psychotic experiences. However, further research is needed to corroborate the proposed mediation hypothesis.

Antisaccade and memory-guided saccade in individuals at ultra-high-risk for bipolar disorder

BACKGROUND

Ultra-high-risk for bipolar disorder (UHR-BD) is an important paradigm to investigate the potential early-stage biomarkers of bipolar disorder, including eye-tracking abnormalities and cognitive functions. Antisaccade (AS) described as looking in the opposite direction of the target, and memory-guided saccade (MGS), identified as maintaining fixation, and remembering the location of the target, were used in this study. The aim of this study was to evaluate the differences in saccadic eye movements between UHR-BD and healthy controls (HCs) via AS-MGS.

METHODS

The study included 28 UHR-BD and 29 HCs. Participants were selected using a structured clinical interview for prodromal symptoms of BD. AS-MGS were measured with parameters like uncorrected errors, anticipatory saccades, and latency. Eye movements were recorded with the EyeLink 1000-Plus eye-tracker.

RESULTS

In the AS, the number of correct saccades was significantly decreased in UHR-BD (p = 0.020). Anticipatory (p = 0.009) and express saccades (p = 0.040) were increased in UHR-BD. In the MGS paradigm, the correct saccades were reduced in UHR-BD (p = 0.031). In addition, anticipatory (p = 0.004) and express saccades (p = 0.012) were significantly increased in cue-screen in UHR-BD.

CONCLUSIONS

To our knowledge, this is the first study to evaluate cognitive functions with eye movements in individuals at UHR-BD. The current findings showed that eye movement functions, particularly in saccadic parameters related to inhibition and spatial perception, may be affected in the UHR-BD group. Therefore, assessment of oculomotor functions may provide observation of clinical and cognitive functions in the early-stage of bipolar disorder. However, further research is needed because the potential effects of medication may affect saccadic results.

Mental time travel for self and others in individuals with a high level of schizotypy

Mental time travel (MTT) is the ability to project oneself to the past or future through mental simulation. Moreover, MTT can involve self-related or other-related information. This study aimed to compare MTT in individuals with high levels of schizotypy and that in their counterparts with low levels of schizotypy. Participants with high (n = 37) and low (n = 37) levels of schizotypy completed an MTT task with four conditions [2 (Condition: self vs. other) × 2 (Time orientation: past vs. future)]. They were required to recall past events that had happened to themselves or to a non-intimate person, and to imagine possible future events that might happen to themselves or to a non-intimate person, related to cue words. Outcome measures included specificity, vividness, sense of experience, emotional valence, emotional intensity, proportion of first-person visual perspective in events, and difficulty in event generation. A 2 (Group: high vs. low levels of schizotypy) × 2 (Condition) × 2 (Time orientation) mixed analysis of variance was conducted on each index. Results showed that self-related MTT was more specific than other-related MTT in low levels of schizotypy participants but not in high levels of schizotypy participants. Participants with a high level of schizotypy reported fewer specific events, and reported events with lower vividness and positive emotion than did those with a low level of schizotypy. Self-related MTT showed higher levels of phenomenological characteristics than did other-related MTT. In conclusion, individuals with a high level of schizotypy have altered MTT, and cannot benefit from the self-advantage effect on the specificity of MTT.

Quotidian Profile of Vergence Angle in Ambulatory Subjects Monitored With Wearable Eye Tracking Glasses

Purpose

Wearable eye trackers record gaze position as ambulatory subjects navigate their environment. Tobii Pro Glasses 3 were tested to assess their accuracy and precision in the measurement of vergence angle.

Methods

Four subjects wore the eye tracking glasses, with their head stabilized, while fixating at a series of distances corresponding to vergence demands of: 0.25, 0.50, 1, 2, 4, 8, 16, and 32°. After these laboratory trials were completed, 10 subjects wore the glasses for a prolonged period while carrying out their customary daily pursuits. A vergence profile was compiled for each subject and compared with interpupillary distance.

Results

In the laboratory, the eye tracking glasses were comparable in accuracy to remote video eye trackers, outputting a mean vergence value within 1° of demand at all angles except 32°. In ambulatory subjects, the glasses were less accurate, due to tracking interruptions and measurement errors, partly mitigated by the application of data filters. Nonetheless, a useful record of vergence behavior was obtained in every subject. Vergence profiles often had a bimodal distribution, reflecting a preponderance of activities at near (mobile phone and computer) or far (driving and walking). As expected, vergence angle correlated with interpupillary distance.

Conclusions

Wearable eye tracking glasses make it possible to compile a nearly continuous record of vergence angle over hours, which can be correlated with the corresponding visual scene viewed by ambulatory subjects.

Translational Relevance

This technology provides new insight into the diversity of human ocular motor behavior and may become useful for the diagnosis of disorders that affect vergence function such as: convergence insufficiency, Parkinson disease, and strabismus.

Perceptual Functioning

Perceptual disorders are not part of the diagnosis criteria for schizophrenia. Yet, a considerable amount of work has been conducted, especially on visual perception abnormalities, and there is little doubt that visual perception is altered in patients. There are several reasons why such perturbations are of interest in this pathology. They are observed during the prodromal phase of psychosis, they are related to the pathophysiology (clinical disorganization, disorders of the sense of self), and they are associated with neuronal connectivity disorders. Perturbations occur at different levels of processing and likely affect how patients interact and adapt to their surroundings. The literature has become very large, and here we try to summarize different models that have guided the exploration of perception in patients. We also illustrate several lines of research by showing how perception has been investigated and by discussing the interpretation of the results. In addition to discussing domains such as contrast sensitivity, masking, and visual grouping, we develop more recent fields like processing at the level of the retina, and the timing of perception.

People with high schizotypy experience more illusions in the Pattern Glare Test: Consistent with the hyperexcitability hypothesis

Individuals diagnosed with schizophrenia spectrum disorders (SSD) exhibit a constellation of sensory and perceptual impairments, including hyporeactivity to external input. However, individuals with SSD also report subjective experiences of sensory flooding, suggesting sensory hyperexcitability. To identify the extent to which behavioural indices of hyperexcitability are related to non-psychotic symptoms of schizophrenia, we tested a non-clinical population measured for schizophrenia-like traits (schizotypy), and a behavioural measure of sensory hyperexcitability, specifically the number of illusions seen in the Pattern Glare Test. Two samples totaling 913 individuals completed an online version of the Schizotypal Personality Questionnaire - Brief Revised (SPQ-BR) and the Pattern Glare Test. Individuals with higher schizotypy traits reported more illusions in the Pattern Glare Test. Additionally, one of the three SPQ-BR factors, the disorganized factor, significantly predicted the number of illusions reported. These data illustrate the potential for research in non-clinical samples to inform clinically relevant research.

A biomarker and endophenotype for anorexia nervosa?

OBJECTIVE

Recent research has suggested that a type of atypical eye movement, called square wave jerks, together with anxiety, may distinguish individuals with anorexia nervosa from those without anorexia nervosa and may represent a biomarker and endophenotype for the illness. The aim of this study was to identify the presence of this proposed marker in individuals currently with anorexia nervosa relative to healthy controls, and to identify the state independence and heritability of this putative marker by exploring whether it also exists in individuals who are weight-restored from anorexia nervosa and first-degree relatives (i.e. sisters of people with anorexia nervosa).

METHODS

Data from 80 female participants (20/group: current anorexia nervosa, weight-restored from anorexia nervosa, sisters of people with anorexia nervosa and healthy controls) were analysed. Square wave jerk rate was acquired during a fixation task, and anxiety was measured with the State Trait Anxiety Inventory.

RESULTS

Current anorexia nervosa, weight-restored from anorexia nervosa and sisters of people with anorexia nervosa groups made significantly more square wave jerks than healthy controls, but did not differ from one another. Square wave jerk rate and anxiety were found to discriminate groups with exceptionally high accuracy (current anorexia nervosa vs healthy control = 92.5%; weight-restored from anorexia nervosa vs healthy control = 77.5%; sisters of people with anorexia nervosa vs healthy control = 77.5%; p < .001).

CONCLUSION

The combination of square wave jerk rate and anxiety was found to be a promising two-element marker for anorexia nervosa, and has the potential to be used as a biomarker or endophenotype to identify people at risk of anorexia nervosa and inform future treatments.

Positive and Negative Symptoms Are Associated with Distinct Effects on Predictive Saccades

The predictive saccade task is a motor learning paradigm requiring saccades to track a visual target moving in a predictable pattern. Previous research has explored extensively anti-saccade deficits observed across psychosis, but less is known about predictive saccade-related mechanisms. The dataset analysed came from the studies of Crawford et al, published in 1995, where neuroleptically medicated schizophrenia and bipolar affective disorder patients were compared with non-medicated patients and control participants using a predictive saccade paradigm. The participant groups consisted of medicated schizophrenia patients (n = 40), non-medicated schizophrenia patients (n = 18), medicated bipolar disorder patients (n = 14), non-medicated bipolar disorder patients (n = 18), and controls (n = 31). The current analyses explore relationships between predictive saccades and symptomatology, and the potential interaction of medication. Analyses revealed that the schizophrenia and bipolar disorder diagnostic categories are indistinguishable in patterns of predictive control across several saccadic parameters, supporting a dimensional hypothesis. Once collapsed into predominantly high-/low- negative/positive symptoms, regardless of diagnosis, differences were revealed, with significant hypometria and lower gain in those with more negative symptoms. This illustrates how the presentation of the deficits is homogeneous across diagnosis, but heterogeneous when surveyed by symptomatology; attesting that a diagnostic label is less informative than symptomatology when exploring predictive saccades.

Sensory gating is related to positive and disorganised schizotypy in contrast to smooth pursuit eye movements and latent inhibition

Since the characteristics and symptoms of both schizophrenia and schizotypy are manifested heterogeneously, it is possible that different endophenotypes and neurophysiological measures (sensory gating and smooth pursuit eye movement errors) represent different clusters of symptoms. Participants (N = 205) underwent a standard conditioned-pairing paradigm to establish their sensory gating ratio, a smooth-pursuit eye-movement task, a latent inhibition task, and completed the Schizotypal Personality Questionnaire. A Multidimensional Scaling analysis revealed that sensory gating was related to positive and disorganised dimensions of schizotypy. Latent inhibition and prepulse inhibition were not related to any dimension of schizotypy. Smooth pursuit eye movement error was unrelated to sensory gating and latent inhibition, but was related to negative dimensions of schizotypy. Our findings suggest that the symptom clusters associated with two main endophenotypes are largely independent. To fully understand symptomology and outcomes of schizotypal traits, the different subtypes of schizotypy (and potentially, schizophrenia) ought to be considered separately rather than together.

Hypothesis of subcortical visual pathway impairment in schizophrenia

Schizophrenia is a severe mental disease involving both neurological and psychiatric abnormalities. Previous studies mainly focus on damage to high-order cognitive dysfunction, which is related to high-level cortical regions such as the prefrontal and temporal lobes. Recent research reveals that impairment of low-level sensory processing occurs in the early stage of schizophrenia, which may be due to impairment of the subcortical magnocellular visual pathway. Moreover, the structure and function of some important nuclei in a subcortical visual pathway are reported to be abnormal in patients with schizophrenia. Inspired by the above evidence, we propose a hypothesis that impairment of the Superior Colliculus-Pulvinar-Amygdala subcortical visual pathway may be involved in the pathological mechanisms of early stages of schizophrenia. And we propose a possible method to detect dysfunction of this subcortical pathway through examining topological processing, which may help early diagnosis of schizophrenia.

Altered Effective Connectivity within an Oculomotor Control Network in Unaffected Relatives of Individuals with Schizophrenia

The ability to rapidly stop or change a planned action is a critical cognitive process that is impaired in schizophrenia. The current study aimed to examine whether this impairment reflects familial vulnerability to schizophrenia across two experiments comparing unaffected first-degree relatives to healthy controls. First, we examined performance on a saccadic stop-signal task that required rapid inhibition of an eye movement. Then, in a different sample, we investigated behavioral and neural responses (using fMRI) during a stop-signal task variant that required rapid modification of a prepared eye movement. Here, we examined differences between relatives and healthy controls in terms of activation and effective connectivity within an oculomotor control network during task performance. Like individuals with schizophrenia, the unaffected relatives showed behavioral evidence for more inefficient inhibitory processes. Unlike previous findings in individuals with schizophrenia, however, the relatives showed evidence for a compensatory waiting strategy. Behavioral differences were accompanied by more activation among the relatives in task-relevant regions across conditions and group differences in effective connectivity across the task that were modulated differently by the instruction to exert control over a planned saccade. Effective connectivity parameters were related to behavioral measures of inhibition efficiency. The results suggest that individuals at familial risk for schizophrenia were engaging an oculomotor control network differently than controls and in a way that compromises inhibition efficiency.

Schizotypy, neuroticism, and saccadic eye movements: New data and meta-analysis

Deficits on saccade tasks, particularly antisaccade performance, have been reliably reported in schizophrenia. However, less evidence is available on saccade performance in relation to schizotypy, a personality constellation harboring risk for schizophrenia. Here, we report a large empirical study of the associations of schizotypy and neuroticism with antisaccade and prosaccade performance (Study I). Additionally, we carried out meta-analyses of the association between schizotypy and antisaccade error rate (Study II). In Study I, N = 526 healthy individuals from the general population aged 18-54 years completed prosaccade and antisaccade tasks as well as the Schizotypal Personality Questionnaire (SPQ). Schizotypy was significantly associated with increased antisaccade error rate, with the disorganized dimension emerging as strongest predictor (β = .118, p = .007). Neuroticism emerged as a significant predictor for prosaccade gain (β = .103, p = .023) and antisaccade latency (β = .101, p = .025). In Study II, random-effects meta-analyses were performed on the published data and those from Study I. Meta-analyses revealed significant associations (all p ≤ .003) of antisaccade error rate with positive (g = 0.37), negative (g = 0.26), disorganized (g = 0.36) and overall schizotypy (g = 0.37). Overall, the present work replicates the association between antisaccade direction errors and schizotypy. Significant findings from meta-analyses provide further evidence of the antisaccade error rate as a putative schizophrenia spectrum marker.

Eye movements in anorexia nervosa: State or trait markers?

OBJECTIVE

Differences in saccadic eye movements are widely reported in mental illnesses, and can indirectly inform our understanding of neurobiological and cognitive underpinnings of psychiatric conditions, including anorexia nervosa (AN). Preliminary research has suggested that individuals with AN may show specific eye movement abnormalities; whether these deficits are representative of state or trait effects is, however, unclear. The aim of this study was to identify whether there are demonstrable differences in performance on saccadic eye movement tasks in individuals with current AN (c-AN), those who are weight-restored from AN (wr-AN), biological sisters of individuals with AN (AN-sis), and healthy controls (HC).

METHODS

Eighty participants took part in the study (n = 20/group). A set of saccadic eye movement tasks was administered, including prosaccade, antisaccade, memory-guided saccade, and visual scanpath tasks.

RESULTS

The c-AN group showed an increased rate of inhibitory errors to 10° targets on the memory-guided saccade task.

DISCUSSION

The results are discussed in terms of the potential role of the superior colliculus in AN, and that the findings may reflect a state measure of AN.

New-Onset Psychosis Associated With a Lesion Localized in the Rostral Tectum: Insights Into Pathway-Specific Connectivity Disrupted in Psychosis

OBJECTIVE

To investigate pathway-specific connectivity disrupted in psychosis.

METHODS

We carried out a case study of a middle-aged patient who presented with new-onset psychosis associated with a space-occupying lesion localized in the right superior colliculus/periaqueductal gray. The study sought to investigate potential connectivity deficits related to the lesion by the use of diffusion tensor imaging and resting-state functional magnetic resonance imaging. To this aim, we generated a functional connectivity map of the patient's brain, centered on the lesion area, and compared this map with the corresponding map of 10 sex- and age-matched control individuals identified from the Max Planck Institute-Leipzig Mind-Brain-Body database.

RESULTS

Our analysis revealed a discrete area in the right rostral tectum, in the immediate vicinity of the lesion, whose activity is inversely correlated with the activity of left amygdala, whereas left amygdala is functionally associated with select areas of the temporal, parietal, and occipital lobes. Based on a comparative analysis of the patient with 10 control individuals, the lesion has impacted on the connectivity of rostral tectum (superior colliculus/periaqueductal gray) with left amygdala as well as on the connectivity of left amygdala with subcortical and cortical areas.

CONCLUSIONS

The superior colliculus/periaqueductal gray might play important roles in the initiation and perpetuation of psychosis, at least partially through dysregulation of left amygdala activity.

Evidence of inverted gravity-driven variation in predictive sensorimotor function

We move our eyes to place the fovea into the part of a viewed scene currently of interest. Recent evidence suggests that each human has signature patterns of eye movements like handwriting which depend on their sensitivity, allocation of attention and experience. Use of implicit knowledge of how earth's gravity influences object motion has been shown to aid dynamic perception. We used a projected ball-tracking task with a plain background offering no context cues to probe the effect of acquired experience about physical laws of gravitation on performance differences of 44 participants under a simulated gravity and an atypical (upward) antigravity condition. Performance measured by the unsigned difference between instantaneous eye and stimulus positions (RMSE) was consistently worse in the antigravity condition. In the vertical RMSE, participants took about 200 ms longer to improve to the best performance for antigravity compared to gravity trials. The antigravity condition produced a divergence of individual performance which was correlated with levels of questionnaire-based quantified traits of schizotypy but not control traits. Grouping participants by high or low traits revealed a negative relationship between schizotypy trait level and both initiation and maintenance of tracking, a result consistent with trait-related impoverished sensory prediction. The findings confirm for the first time that where cues enabling exact estimation of acceleration are unavailable, knowledge of gravity contributes to dynamic prediction improving motion processing. With acceleration expectations violated, we demonstrate that antigravity tracking could act as a multivariate diagnostic window into predictive brain function.

The Potential of Game-Based Digital Biomarkers for Modeling Mental Health

BACKGROUND

Assessment for mental health is performed by experts using interview techniques, questionnaires, and test batteries and following standardized manuals; however, there would be myriad benefits if behavioral correlates could predict mental health and be used for population screening or prevalence estimations. A variety of digital sources of data (eg, online search data and social media posts) have been previously proposed as candidates for digital biomarkers in the context of mental health. Playing games on computers, gaming consoles, or mobile devices (ie, digital gaming) has become a leading leisure activity of choice and yields rich data from a variety of sources.

OBJECTIVE

In this paper, we argue that game-based data from commercial off-the-shelf games have the potential to be used as a digital biomarker to assess and model mental health and health decline. Although there is great potential in games developed specifically for mental health assessment (eg, Sea Hero Quest), we focus on data gathered "in-the-wild" from playing commercial off-the-shelf games designed primarily for entertainment.

METHODS

We argue that the activity traces left behind by natural interactions with digital games can be modeled using computational approaches for big data. To support our argument, we present an investigation of existing data sources, a categorization of observable traits from game data, and examples of potentially useful game-based digital biomarkers derived from activity traces.

RESULTS

Our investigation reveals different types of data that are generated from play and the sources from which these data can be accessed. Based on these insights, we describe five categories of digital biomarkers that can be derived from game-based data, including behavior, cognitive performance, motor performance, social behavior, and affect. For each type of biomarker, we describe the data type, the game-based sources from which it can be derived, its importance for mental health modeling, and any existing statistical associations with mental health that have been demonstrated in prior work. We end with a discussion on the limitations and potential of data from commercial off-the-shelf games for use as a digital biomarker of mental health.

CONCLUSIONS

When people play commercial digital games, they produce significant volumes of high-resolution data that are not only related to play frequency, but also include performance data reflecting low-level cognitive and motor processing; text-based data that are indicative of the affective state; social data that reveal networks of relationships; content choice data that imply preferred genres; and contextual data that divulge where, when, and with whom the players are playing. These data provide a source for digital biomarkers that may indicate mental health. Produced by engaged human behavior, game data have the potential to be leveraged for population screening or prevalence estimations, leading to at-scale, nonintrusive assessment of mental health.

Saccadic eye movements in different dimensions of schizophrenia and in clinical high-risk state for psychosis

BACKGROUND

Oculomotor dysfunction is one of the most replicated findings in schizophrenia. However the association between saccadic abnormalities and particular clinical syndromes remains unclear. The assessment of saccadic movements in schizophrenia patients as well as in clinical high-risk state for psychosis individuals (CHR) as a part of schizophrenia continuum may be useful in validation of saccadic movements as a possible biomarker.

METHODS

The study included 156 patients who met the ICD-10 criteria for schizophrenia: 42 individuals at clinical high-risk-state for psychosis and 61 healthy controls. The schizophrenia patients had three subgroups based on the sum of the global SAPS and SANS scores: (1) patients with predominantly negative symptoms (NS, n = 62); (2) patients with predominantly positive symptoms (PS, n = 54) (3) patients with predominantly disorganization symptoms (DS, n = 40). CHR subjects were characterized by the presence of one of the groups of criteria: (1) Ultra High Risk criteria, (2) Basic Symptoms criteria or (3) negative symptoms and formal thought disorders. Horizontal eye movements were recorded by using videonystagmograph. We measured peak velocity, latency and accuracy in prosaccade, antisaccade and predictive saccade tasks as well as error rates in the antisaccade task.

RESULTS

Schizophrenia patients performed worse than controls in predictive, reflexive and antisaccade tasks. Oculomotor parameters of NS were different from the other groups of patients. Latencies of predictive and reflexive saccades were significantly longer than in controls only in the NS group. The accuracy of predictive saccades was also different from controls only in the NS schizophrenia group. More prominent loss of accuracy of reflexive saccades was found in the DS group and it significantly differed from the one in other groups. Participants from DS group made more errors in antisaccade task compared to NS and PS groups. CHR subjects performed worse than controls as measured by the accuracy of reflexive saccades and antisaccades.

CONCLUSIONS

The study confirms the existence of different relations between the symptom dimensions of schizophrenia and saccades tasks performances. Saccadic abnormalities were revealed in the clinical (schizophrenia) and pre-clinical (clinical high risk) populations that provide further evidence for assessing saccadic abnormalities as a possible neurobiological marker for schizophrenia.

Working Memory and Attention Influence Antisaccade Error Rate in Schizophrenia

Objectives: Antisaccade error rate has been proposed to be one of the most promising endophenotypes for schizophrenia. Increased error rate in patients has been associated with working memory, attention and other executive function impairments. The relationship between antisaccade error rate and other neuropsychological processes in patients compared to healthy controls has not been explored in depth. This study aimed to replicate the finding of heightened antisaccade error rate in patients and determine which cognitive processes were most strongly associated with antisaccade error rate in both patients and controls. In addition, the study investigated whether different antisaccade task paradigms engage different cognitive processes. Methods: One hundred and ninety-one participants (54 patients with schizophrenia/schizoaffective disorder and 137 controls) completed the antisaccade task, which included both gap and step task parameters. Neuropsychological measures were obtained using the MCCB and the Stroop task. Results: The current study replicated a pronounced antisaccade error rate deficit in patients. In patients, working memory variance was most significantly associated with antisaccade errors made during the step condition, while attentional processes were most associated with errors made during the gap condition. In controls, overall global cognitive performance was most associated with antisaccade rates for both gap and step conditions. Conclusions: The current study demonstrates that in schizophrenia patients, but not controls, elevated antisaccade error rate is associated with attention and working memory, but not with global cognitive impairment or psychopathological processes. Our novel findings demonstrate that the gap and step conditions of the antisaccade task engage different cognitive processes. (JINS, 2019, 25, 174-183).

Visual training program for body dysmorphic disorder: protocol for a novel intervention pilot and feasibility trial

Background

Body dysmorphic disorder (BDD) is a characterised by perceived defects or flaws in appearance which are associated with distressing thoughts, repetitive or obsessive behaviours, and significant impairment in social and occupational functioning. A core feature of BDD involves abnormalities of visual processing, although this is not typically a focus of psychological and psychiatric treatments. While current treatments generally show moderate effectiveness in the short-term, those with BDD can have high relapse rates, as they still 'see' their flaws or defects. The current research trials a visual training program designed to remediate visual abnormalities and reduce symptom severity of BDD.

Methods

This is a single-group open-label pilot study assessing the feasibility and potential efficacy of a 10-week visual training program. This pilot trial will be conducted at Swinburne University of Technology, Melbourne, Australia, and will recruit up to 20 participants diagnosed with BDD. These participants will complete pre- and post-assessments and a 10-week visual training program encompassing three phases of basic visual processing, face and emotion recognition, and self-perception. The primary outcomes focus on feasibility and acceptability of the intervention, with secondary outcomes exploring clinical outcomes related to symptom severity, quality of life and eye movements.

Discussion

This pilot trial will translate the empirical findings of abnormalities in visual processing among those diagnosed with BDD, to an innovative treatment method across a range of visual processing levels. This trial will assess the feasibility and potential efficacy of such a visual training program, paving the way for further research including a future definitive randomised control trial.

Trial registration

Australian New Zealand Clinical Trial Registry, ACTRN 12618000274279, Registered 22nd February 2018.

Inhibition failures and late errors in the antisaccade task: influence of cue delay

In the antisaccade task participants are required to saccade in the opposite direction of a peripheral visual cue (PVC). This paradigm is often used to investigate inhibition of reflexive responses as well as voluntary response generation. However, it is not clear to what extent different versions of this task probe the same underlying processes. Here, we explored with the Stochastic Early Reaction, Inhibition, and late Action (SERIA) model how the delay between task cue and PVC affects reaction time (RT) and error rate (ER) when pro- and antisaccade trials are randomly interleaved. Specifically, we contrasted a condition in which the task cue was presented before the PVC with a condition in which the PVC served also as task cue. Summary statistics indicate that ERs and RTs are reduced and contextual effects largely removed when the task is signaled before the PVC appears. The SERIA model accounts for RT and ER in both conditions and better so than other candidate models. Modeling demonstrates that voluntary pro- and antisaccades are frequent in both conditions. Moreover, early task cue presentation results in better control of reflexive saccades, leading to fewer fast antisaccade errors and more rapid correct prosaccades. Finally, high-latency errors are shown to be prevalent in both conditions. In summary, SERIA provides an explanation for the differences in the delayed and nondelayed antisaccade task. NEW & NOTEWORTHY In this article, we use a computational model to study the mixed antisaccade task. We contrast two conditions in which the task cue is presented either before or concurrently with the saccadic target. Modeling provides a highly accurate account of participants' behavior and demonstrates that a significant number of prosaccades are voluntary actions. Moreover, we provide a detailed quantitative analysis of the types of error that occur in pro- and antisaccade trials.

Ketamine Alters Lateral Prefrontal Oscillations in a Rule-Based Working Memory Task

Acute administration of N-methyl-D-aspartate receptor (NMDAR) antagonists in healthy humans and animals produces working memory deficits similar to those observed in schizophrenia. However, it is unclear whether they also lead to altered low-frequency (≤60 Hz) neural oscillatory activities similar to those associated with schizophrenia during working memory processes. Here, we recorded local field potentials (LFPs) and single-unit activity from the lateral prefrontal cortex (LPFC) of three male rhesus macaque monkeys while they performed a rule-based prosaccade and antisaccade working memory task both before and after systemic injections of a subanesthetic dose (≤0.7 mg/kg) of ketamine. Accompanying working-memory impairment, ketamine enhanced the low-gamma-band (30-60 Hz) and dampened the beta-band (13-30 Hz) oscillatory activities in the LPFC during both delay periods and intertrial intervals. It also increased task-related alpha-band activities, likely reflecting compromised attention. Beta-band oscillations may be especially relevant to working memory processes because stronger beta power weakly but significantly predicted shorter saccadic reaction time. Also in beta band, ketamine reduced the performance-related oscillation as well as the rule information encoded in the spectral power. Ketamine also reduced rule information in the spike field phase consistency in almost all frequencies up to 60 Hz. Our findings support NMDAR antagonists in nonhuman primates as a meaningful model for altered neural oscillations and synchrony, which reflect a disorganized network underlying the working memory deficits in schizophrenia.SIGNIFICANCE STATEMENT Low doses of ketamine, an NMDAR blocker, produce working memory deficits similar to those observed in schizophrenia. In the lateral prefrontal cortex, a key brain region for working memory, we found that ketamine altered neural oscillatory activities in similar ways that differentiate schizophrenic patients and healthy subjects during both task and nontask periods. Ketamine induced stronger gamma (30-60 Hz) and weaker beta (13-30 Hz) oscillations, reflecting local hyperactivity and reduced long-range communications. Furthermore, ketamine reduced performance-related oscillatory activities, as well as the rule information encoded in the oscillations and in the synchrony between single-cell activities and oscillations. The ketamine model helps link the molecular and cellular basis of neural oscillatory changes to the working memory deficit in schizophrenia.