Early auditory processing evoked potentials (N100) show a continuum of blunting from clinical high risk to psychosis in a pediatric sample

The impact of virtual reality and distractors on attentional processes: insights from EEG

Virtual reality (VR) allows to create controlled scenarios in which the quantity of stimuli can be modulated, as happen in real-life, where humans are subjected to various multisensory-often overlapping-stimuli. The present research aimed to study changes in attentional processes within an auditory oddball paradigm during a virtual exploration, while varying the amount of distractors. Twenty healthy volunteers underwent electroencephalography (EEG) during three different experimental conditions: an auditory oddball without VR (No-VR condition), an auditory oddball during VR exploration without distractors (VR-Empty condition), and an auditory oddball during VR exploration with a high level of distractors (VR-Full condition). Event-related potentials (ERPs) were computed averaging epochs of EEGs and analyzing peaks at 100 ms (N100) and 300 ms (P300) latencies. Results showed modulation of N100 amplitude in Fz and of P300 amplitude in Pz. Statistically significant differences in latency were observed only for P300 where the latency results delayed from the No-VR to VR-Full. The scalp topography revealed for P100 no significant differences between frequent and rare stimuli in either the No-VR and VR-Empty conditions. However, significant results were found in N100 in VR-Full condition. For P300, results showed differences between frequent and rare stimuli, in every condition. However, this difference is gradually less widespread from No-VR condition to the VR-Full. The emerging integration of VR with EEG may have important implications for studying brain attentional processing.

Long-latency auditory evoked response amplitudes at first episode of psychosis predict six-month recovery in positive symptom severity

Predicting treatment response would facilitate individualized medical treatment in first-episode psychosis (FEP). We examined relationships between auditory-evoked M100 and longitudinal change in positive symptoms in FEP. M100 was measured from source-resolved magnetoencephalography and symptoms were assessed at initial contact and six months later. M100 at baseline significantly predicted symptom change. Larger M100 at baseline predicted symptom improvement, as did shorter untreated psychosis. Shorter untreated psychosis also correlated with larger M100, and M100 mediated the effect of untreated psychosis on treatment response. Thus, M100 may provide a proximal and objective index of untreated psychosis and a viable route to individualized medicine.

Recovery of auditory evoked response attentional gain modulation following the first psychotic episode indexes improvements in symptom severity

Attentional control of auditory N100/M100 gain is reduced in individuals with first-episode psychosis (FEP). Persistent problems with executive modulation of auditory sensory activity may impact multiple aspects of psychosis. As a follow-up to our prior work reporting deficits in attentional M100 gain modulation in auditory cortex, we examined changes in M100 gain modulation longitudinally, and further examined relationships between auditory M100 and symptoms of psychosis. We compared auditory M100 in auditory sensory cortex between 21 FEP and 29 matched healthy participants and between timepoints separated by 220 ± 100 days. Magnetoencephalography data were recorded while participants alternately attended or ignored tones in an auditory oddball task. M100 was measured as the average of 80-140 ms post-stimulus in source-localized evoked responses within bilateral auditory cortex. Symptoms were assessed using the PANSS and PSYRATS. M100 amplitudes, attentional modulation of M100 amplitudes, and symptom severity all improved in FEP over time. Further, improvement in M100 modulation correlated with improvements in negative symptoms (PANSS) as well as physical, cognitive, and emotional components of hallucinations (PSYRATS). Conversely, improvements in the overall size of the M100, rather than the difference between active and passive M100 amplitudes, were related to worsening of positive symptoms (PANSS) and physical components of hallucinations. Results indicate a link between symptoms (particularly auditory hallucinations) and auditory cortex neurophysiology in FEP, where auditory attention and auditory sensation have opposed relationships to symptom change. These findings may inform current models of psychosis etiology and could provide nonpharmaceutical avenues for early intervention.

Auditory N100 amplitude deficits predict conversion to psychosis in the North American Prodrome Longitudinal Study (NAPLS-2) cohort

BACKGROUND

The auditory N100 is an event related potential (ERP) that is reduced in schizophrenia, but its status in individuals at clinical high risk for psychosis (CHR) and its ability to predict conversion to psychosis remains unclear. We examined whether N100 amplitudes are reduced in CHR subjects relative to healthy controls (HC), and this reduction predicts conversion to psychosis in CHR.

METHODS

Subjects included CHR individuals (n = 552) and demographically similar HC subjects (n = 236) from the North American Prodrome Longitudinal Study. Follow-up assessments identified CHR individuals who converted to psychosis (CHRC; n = 73) and those who did not (CHR-NC; n = 225) over 24 months. Electroencephalography data were collected during an auditory oddball task containing Standard, Novel, and Target stimuli. N100 peak amplitudes following each stimulus were measured at electrodes Cz and Fz.

RESULTS

The CHR subjects had smaller N100 absolute amplitudes than HC subjects at Fz (F(1,786) = 4.00, p 0.046). A model comparing three groups (CHRC, CHR-NC, HC) was significant for Group at the Cz electrode (F(2,531) = 3.58, p = 0.029). Both Standard (p = 0.019) and Novel (p = 0.017) stimuli showed N100 absolute amplitude reductions in CHR-C relative to HC. A smaller N100 amplitude at Cz predicted conversion to psychosis in the CHR cohort (Standard: p = 0.009; Novel: p = 0.001) and predicted shorter time to conversion (Standard: p = 0.013; Novel: p = 0.001).

CONCLUSION

N100 amplitudes are reduced in CHR individuals which precedes the onset of psychosis. N100 deficits in CHR individuals predict a greater likelihood of conversion to psychosis. Our results highlight N100's utility as a biomarker of psychosis risk.

Effects of the glycine transporter-1 inhibitor iclepertin (BI 425809) on sensory processing, neural network function, and cognition in animal models related to schizophrenia

N-methyl-D-aspartate (NMDA) receptor hypofunction leading to neural network dysfunction is thought to play an important role in the pathophysiology of cognitive impairment associated with schizophrenia (CIAS). Increasing extracellular concentrations of the NMDA receptor co-agonist glycine through inhibition of glycine transporter-1 (GlyT1) has the potential to treat CIAS by improving cortical network function through enhanced glutamatergic signaling. Indeed, the novel GlyT1 inhibitor iclepertin (BI 425809) improved cognition in a recent clinical study in patients with schizophrenia. The present study tested the ability of iclepertin to reverse MK-801-induced deficits in auditory sensory processing and cortical network function using electroencephalography (EEG) to measure auditory event-related potentials (AERP) and 40 Hz auditory steady-state response (ASSR). In addition, improvements in memory performance with iclepertin were evaluated using the T-maze spontaneous alternation test in MK-801-treated mice and the social recognition test in naïve rats. Iclepertin reversed MK-801-induced deficits in the AERP readouts N1 amplitude and N1 gating, as well as 40 Hz ASSR power and inter-trial coherence. Additionally, iclepertin significantly attenuated an MK-801-induced increase in basal gamma power. Furthermore, iclepertin reversed MK-801-induced working memory deficits in mice and improved social recognition memory performance in rats. Overall, this study demonstrates that inhibition of GlyT1 is sufficient to attenuate MK-801-induced deficits in translatable EEG parameters relevant to schizophrenia. Moreover, iclepertin showed memory-enhancing effects in rodent cognition tasks, further demonstrating the potential for GlyT1 inhibition to treat CIAS. Significance Statement Despite the significant patient burden caused by cognitive impairment associated with schizophrenia, there are currently no approved pharmacotherapies. In this preclinical study, the novel glycine transporter inhibitor iclepertin (BI 425809) reversed sensory processing deficits and neural network dysfunction evoked by inhibition of N-methyl-D-aspartate (NMDA) receptors, and enhanced working memory performance and social recognition in rodents. These findings support previous clinical evidence for the pro-cognitive effects of iclepertin.

Neurophysiology in psychosis: The quest for disease biomarkers

Psychotic disorders affect 3% of the population at some stage in life, are a leading cause of disability, and impose a great economic burden on society. Major breakthroughs in the genetics of psychosis have not yet been matched by an understanding of its neurobiology. Biomarkers of perception and cognition obtained through non-invasive neurophysiological tools, especially EEG, offer a unique opportunity to gain mechanistic insights. Techniques for measuring neurophysiological markers are inexpensive and ubiquitous, thus having the potential as an accessible tool for patient stratification towards early treatments leading to better outcomes. In this paper, we review the literature on neurophysiological markers for psychosis and their relevant disease mechanisms, mainly covering event-related potentials including P50/N100 sensory gating, mismatch negativity, and the N100 and P300 waveforms. While several neurophysiological deficits are well established in patients with psychosis, more research is needed to study neurophysiological markers in their unaffected relatives and individuals at clinical high risk. We need to harness EEG to investigate markers of disease risk as key steps to elucidate the aetiology of psychosis and facilitate earlier detection and treatment.

Annual Research Review: Prevention of psychosis in adolescents - systematic review and meta-analysis of advances in detection, prognosis and intervention

BACKGROUND

The clinical high-risk state for psychosis (CHR-P) paradigm has facilitated the implementation of psychosis prevention into clinical practice; however, advancements in adolescent CHR-P populations are less established.

METHODS

We performed a PRISMA/MOOSE-compliant systematic review of the Web of Science database, from inception until 7 October 2019, to identify original studies conducted in CHR-P children and adolescents (mean age <18 years). Findings were systematically appraised around core themes: detection, prognosis and intervention. We performed meta-analyses (employing Q statistics and I ² test) regarding the proportion of CHR-P subgroups, the prevalence of baseline comorbid mental disorders, the risk of psychosis onset and the type of interventions received at baseline. Quality assessment and publication bias were also analysed.

RESULTS

Eighty-seven articles were included (n = 4,667 CHR-P individuals). Quality of studies ranged from 3.5 to 8 (median 5.5) on a modified Newcastle-Ottawa scale. Detection: Individuals were aged 15.6 ± 1.2 years (51.5% males), mostly (83%) presenting with attenuated positive psychotic symptoms. CHR-P psychometric accuracy improved when caregivers served as additional informants. Comorbid mood (46.4%) and anxiety (31.4%) disorders were highly prevalent. Functioning and cognition were impaired. Neurobiological studies were inconclusive.

PROGNOSIS

Risk for psychosis was 10.4% (95%CI: 5.8%-18.1%) at 6 months, 20% (95%CI: 15%-26%) at 12 months, 23% (95%CI: 18%-29%) at 24 months and 23.3% (95%CI: 17.3%-30.7%) at ≥36 months.

INTERVENTIONS

There was not enough evidence to recommend one specific treatment (including cognitive behavioural therapy) over the others (including control conditions) to prevent the transition to psychosis in this population. Randomised controlled trials suggested that family interventions, cognitive remediation and fish oil supplementation may improve cognition, symptoms and functioning. At baseline, 30% of CHR-P adolescents were prescribed antipsychotics and 60% received psychotherapy.

CONCLUSIONS

It is possible to detect and formulate a group-level prognosis in adolescents at risk for psychosis. Future interventional research is required.

The song of Anorexia Nervosa: a specific evoked potential response to musical stimuli in affected participants

PURPOSE

Research applying electroencephalography (EEG) to Anorexia Nervosa (AN) is still limited, even though in other psychiatric disorders EEG has permitted to find out the hallmarks of the disorder. The aim of the study was to explore whether EEG basal activity and reactivity to musical stimulation differ in participants with AN as compared to healthy subjects (HS).

METHODS

Twenty female participants (respectively 10 with AN and 10 healthy controls) were administered a battery of psychometric tests and underwent EEG under three different conditions: (1) at baseline; (2) after a generic music stimulation; and (3) after a favorite musical stimulation.

RESULTS

In participants with AN, basal EEG showed the higher absolute amplitude of cortical slow waves (theta) in the parieto-occipital and temporal derivations, with a deficit in the beta band. In AN, there was a higher N100 latency and a reduced P300 latency compared to HS. While the N100 and P300 latencies were sensitive to the musical stimulus in HS, there was no difference after music stimulation in AN.

CONCLUSION

These data suggest that AN is accompanied by a state of brain hyperarousal with abnormal reactivity to environmental stimuli, similar to the state of HS after musical stimulation. If confirmed, this finding may have treatment implications.

LEVEL OF EVIDENCE

III, Evidence obtained from well-designed cohort or case-control analytic studies.

Electroencephalography and Event-Related Potential Biomarkers in Individuals at Clinical High Risk for Psychosis

Clinical outcomes vary among youths at clinical high risk for psychosis (CHR-P), with approximately 20% progressing to full-blown psychosis over 2 to 3 years and 30% achieving remission. Recent research efforts have focused on identifying biomarkers that precede psychosis onset and enhance the accuracy of clinical outcome prediction in CHR-P individuals, with the ultimate goal of developing staged treatment approaches based on the individual's level of risk. Identifying such biomarkers may also facilitate progress toward understanding pathogenic mechanisms underlying psychosis onset, which may support the development of mechanistically informed early interventions for psychosis. In recent years, electroencephalography-based event-related potential measures with established sensitivity to schizophrenia have gained traction in the study of CHR-P and its clinical outcomes. In this review, we describe the evidence for event-related potential abnormalities in CHR-P and discuss how they inform our understanding of information processing deficits as vulnerability markers for emerging psychosis and as indicators of future outcomes. Among the measures studied, P300 and mismatch negativity are notable because deficits predict conversion to psychosis and/or CHR-P remission. However, the accuracy with which these and other measures predict outcomes in CHR-P has been obscured in the prior literature by the tendency to only report group-level differences, underscoring the need for inclusion of individual predictive accuracy metrics in future studies. Nevertheless, both P300 and mismatch negativity show promise as electrophysiological markers of risk for psychosis, as target engagement measures for clinical trials, and as potential translational bridges between human studies and animal models focused on novel drug development for early psychosis.

P300 amplitude attenuation in high risk and early onset psychosis youth

Little research has investigated the use of electrophysiological biomarkers in childhood and adolescence to distinguish early onset psychosis and the clinical high risk state. The P300 evoked potential is a robust neurophysiological marker of schizophrenia that is dampened in patients with schizophrenia and, less consistently, in those with affective psychoses and those at clinical high risk for psychosis (CHR). How it may differ between patients with psychotic disorders (PS) and CHR is less studied, especially in youth. The current study compared P300 activity among children and adolescents, aged 5-18 years, at CHR (n = 43), with PS (n = 28), and healthy controls (HC; n = 24). Participants engaged in an auditory event-related potential (ERP) task to elicit a P300 response and completed clinical interviews to verify symptoms and diagnoses. Linear regression analyses revealed a decrease in P300 amplitude with increased severity of psychotic symptoms. PS participants showed a diminished P300 response compared to those at CHR and HC, particularly among adolescents aged 13-18. This response was most evident at centroparietal and parietal locations in the right hemisphere. The findings suggest that high risk and psychotic symptomatology is linked to attenuated parietal P300 activity in youth as young as 13 years. Further exploration of the P300 as a biomarker for psychosis in very young patients could inform tailored, appropriate interventions at early stages of disease progression. Future research should evaluate whether specific phenotypic and genotypic characteristics are differentially associated with neurophysiological biomarkers and whether P300 attenuation in CHR youth can predict later symptom severity.

Neurobiological approaches to the study of clinical and genetic high risk for developing psychosis

Research on neurobiological impairments in clinical and genetic high risk for developing psychosis individuals (CHR) has identified several brain abnormalities that impact both brain structure and function. The current review will discuss research examining brain abnormalities in clinical and genetic high risk for psychosis using magnetic resonance imaging (MRI) focusing on structural brain abnormalities, diffusion tensor imaging (DTI) focusing on the integrity of white matter tracks, functional MRI focusing on functional brain abnormalities, and EEG and event related potential (ERP) methodologies focusing on indices of cognitive dysfunction in CHR. Studies conducted across these different methodologies sought to identify brain regions and brain processes that would distinguish between those high risk individuals who converted to psychosis versus those who did not. In addition, in some of the studies, the distinction was made between individuals who converted to psychosis, those who did not, and those individuals who remained clinically symptomatic while not converting to psychosis. The brain regions most often identified as abnormal in this subject group were the brain areas often found abnormal in schizophrenia, including frontal and temporal regions. Similarly, several cognitive processes often found to be abnormal in schizophrenia have been also found impaired in CHR.

[The schizophrenic's chilhood]

Pathology of adolescence and young adult, schizophrenia can begin in very rare cases during childhood. Two early clinical forms of the disorder have been identified by epidemiological studies: one beginning at the age of 15; the other around 9 years old; While many questions remain unsanswered about the neurobiological and environmental factors - common or distinct - of these two clinical phenotype, both are related to a profoun and lasting alteration of the neurocognitive development whose origin would clearly go back to infancy or to the antenal period. Here we will present a possible story back of schizophrenia in the light of the latest neuroscientific studies in imagery and genetics from adolescence to antenal period.

Social impairment and social language deficits in children and adolescents with and at risk for psychosis

INTRO

One of the more debilitating functional outcomes of schizophrenia-spectrum disorders is social impairment. Previous studies have identified impaired social functioning both in the prodromal phase of psychosis and after acute symptoms abate, suggesting that social impairment represents a core deficit in psychosis not directly linked to psychotic episodes or symptom severity. To date, research in this area has focused primarily on adult populations rather than children, and has not directly assessed social language in individuals across the psychosis continuum.

METHODS

81 youth ages 7-18 (N = 24 Typically Developing [TD], N = 36 Clinical High Risk [CHR], N = 21 Psychotic Disorder [PD]) were recruited. Youth participants were administered the Social Language Development Test (SLDT), and parent(s)/guardian(s) completed the Social Responsiveness Scale-II (SRS-II).

RESULTS

Social language ability was not associated with social impairment. PD participants performed significantly worse on the SLDT than TD participants. CHR and PD participants were both rated as having experienced significantly greater social impairment than TD participants on every subscale of the SRS-II.

DISCUSSION

Deficits in social language ability and social functioning are strong candidates for phenotypic markers of psychosis, and may be evident earlier in development than previous work has demonstrated. Additionally, the severity of social impairment did not differ between CHR and PD participants, further supporting that social cognitive deficits and social impairment, while related to symptom severity, are discrete deficits in individuals with and at risk for psychosis. These results highlight the importance of addressing social skills for individuals presenting in clinical settings with psychotic symptoms, including children.

Young children with psychotic symptoms and risk for suicidal thoughts and behaviors: a research note

Objective

Suicidal thoughts and behaviors (STBs) are prevalent among youth with psychotic disorders (PD) relative to the general population. Recent research now suggests that STBs may present during the prodromal phase of the disease, or the clinical high risk (CHR) state. While this knowledge is important for the development of suicide prevention strategies in adolescent and adult populations, it remains unclear whether risk for suicide extends to children with or at risk for psychosis. The current study is an extension of previous work assessing STBs in youth across the psychosis continuum. We examine STBs in 37 CHR and PD children ages 7–13 years old, and further explore the prodromal symptom correlates of STB severity among CHR children.

Results

CHR and PD children endorsed STBs with a frequency and severity similar to what is observed in older CHR and PD populations. A number of children had never previously vocalized their suicidal plans or intent. Among CHR children, Social Anhedonia and Odd Behavior or Appearance were significantly correlated with STB severity. These findings underscore the importance of screening for STBs even in young children presenting with psychotic symptoms.

Event-Related Potentials in the Clinical High-Risk (CHR) State for Psychosis: A Systematic Review

There is emerging evidence that identification and treatment of individuals in the prodromal or clinical high-risk (CHR) state for psychosis can reduce the probability that they will develop a psychotic disorder. Event-related brain potentials (ERPs) are a noninvasive neurophysiological technique that holds promise for improving our understanding of neurocognitive processes underlying the CHR state. We aimed to systematically review the current literature on cognitive ERP studies of the CHR population, in order to summarize and synthesize the results, and their implications for our understanding of the CHR state. Across studies, amplitudes of the auditory P300 and duration mismatch negativity (MMN) ERPs appear reliably reduced in CHR individuals, suggesting that underlying impairments in detecting changes in auditory stimuli are a sensitive early marker of the psychotic disease process. There are more limited data indicating that an earlier-latency auditory ERP response, the N100, is also reduced in amplitude, and in the degree to which it is modulated by stimulus characteristics, in the CHR population. There is also evidence that a number of auditory ERP measures (including P300, MMN and N100 amplitudes, and N100 gating in response to repeated stimuli) can further refine our ability to detect which CHR individuals are most at risk for developing psychosis. Thus, further research is warranted to optimize the predictive power of algorithms incorporating these measures, which could help efforts to target psychosis prevention interventions toward those most in need.

Clinical high risk for psychosis in children and adolescents: a systematic review

The concept of being at risk for psychosis has been introduced both for adults and children and adolescents, but fewer studies have been conducted in the latter population. The aim of this study is to systematically review the articles associated with clinical description, interventions, outcome and other areas in children and adolescents at risk for psychosis. We searched in MEDLINE/PubMed and PsycINFO databases for articles published up to 30/06/16. Reviewed articles were prospective studies; written in English; original articles with Clinical High Risk (CHR) for psychosis samples; and mean age of samples younger than 18 years. From 103 studies initially selected, 48 met inclusion criteria and were systematically reviewed. Studies show that CHR children and adolescents present several clinical characteristics at baseline, with most attenuated positive-symptom inclusion criteria observed, reporting mostly perceptual abnormalities and suspiciousness, and presenting comorbid conditions such as depressive and anxiety disorders. CHR children and adolescents show lower general intelligence and no structural brain changes compared with controls. Original articles reviewed show rates of conversion to psychosis between 17 and 20% at 1 year follow-up and between 7 and 21% at 2 years. While 36% of patients recovered from their CHR status at 6-year follow-up, 40% still met CHR criteria. Studies in children and adolescents with CHR were conducted with different methodologies, assessments tools and small samples. It is important to conduct studies on psychopharmacological and psychological treatment, as well as replication of the few studies found.

Suicidal behaviors and their relationship with psychotic-like symptoms in children and adolescents at clinical high risk for psychosis

BACKGROUND

Previous research has demonstrated elevated rates of suicide attempts and ideation in individuals with psychosis. This study investigated rates and severity of suicidal behavior in youth with and at clinical high risk for psychosis, and examined the positive, negative, and disorganized symptoms associated with suicidal behaviors among the clinical high risk group.

METHODS

Eighty-six youth ages 7-18 (n=21 non-clinical controls [NCC], n=40 clinical high risk [CHR], n=25 diagnosed psychotic disorder [PD]) were recruited. CHR and PD participants were identified using the Structured Interview for Prodromal Symptoms (SIPS) and Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version (KSADS-PL). All participants completed the Suicide Behaviors Questionnaire-Revised (SBQ-R).

RESULTS

Findings indicated significantly higher levels of suicidal behavior among CHR and PD relative to NCC participants (F=7.64, p=0.001). 17.5% of CHR participants had previously attempted suicide. Dysphoric Mood and Odd Behavior or Appearance were significantly correlated with suicidal behavior severity among CHR youth.

CONCLUSION

Suicidal behavior was observed with greater frequency and severity in the CHR and PD groups than in the NCC group. CHR suicidal behavior severity was correlated most strongly with Dysphoric Mood and Odd Behavior or Appearance, a relationship which warrants further investigation.