Relationship of prolonged acoustic startle latency to diagnosis and biotype in the bipolar-schizophrenia network on intermediate phenotypes (B-SNIP) cohort

Reduced amplitude and slowed latency of the acoustic startle response in adolescents and adults with 22q11.2 deletion syndrome

BACKGROUND

22q11.2 deletion syndrome (22q11DS) is one of the most robust genetic predictors of psychosis and other psychiatric illnesses. In this study, we examined 22q11DS subjects' acoustic startle responses (ASRs), which putatively index psychosis risk. Latency of the ASR is a presumptive marker of neural processing speed and is prolonged (slower) in schizophrenia. ASR measures correlate with increased psychosis risk, depend on glutamate and dopamine receptor signaling, and could serve as translational biomarkers in interventions for groups at high psychosis risk.

METHODS

Startle magnitude, latency, and prepulse inhibition were assessed with a standard acoustic startle paradigm in 31 individuals with 22q11.2DS and 32 healthy comparison (HC) subjects. Surface electrodes placed on participants' orbicularis oculi recorded the electromyographic signal in ASR eyeblinks. Individuals without measurable startle blinks in the initial habituation block were classified as non-startlers.

RESULTS

Across the startle session, the ASR magnitude was significantly lower in 22q11DS subjects than HCs because a significantly higher proportion of 22q11DS subjects were non-startlers. Latency of the ASR to pulse-alone stimuli was significantly slower in 22q11DS than HC subjects. Due to the overall lower 22q11DS startle response frequency and magnitudes prepulse inhibition could not be analyzed.

CONCLUSIONS

Reduced magnitude and slow latency of 22q11DS subjects' responses suggest reduced central nervous system and neuronal responsiveness. These findings are consistent with significant cognitive impairments observed in 22q11DS subjects. Further research is needed to untangle the connections among basic neurotransmission dysfunction, psychophysiological responsiveness, and cognitive impairment.

Identifying psychosis subtypes use individualized covariance structural differential networks and multi-site clustering

BACKGROUND

Similarities among schizophrenia (SZ), schizoaffective disorder (SAD) and bipolar disorder (BP) including clinical phenotypes, brain alterations and risk genes, make it challenging to perform reliable separation among them. However, previous subtype identification that transcend traditional diagnostic boundaries were based on group-level neuroimaging features, ignoring individual-level inferences.

METHODS

455 psychoses (178 SZs, 134 SADs and 143 BPs), their first-degree relatives (N = 453) and healthy controls (HCs, N = 220) were collected from Bipolar-Schizophrenia Network on Intermediate Phenotypes (B-SNIP I) consortium. Individualized covariance structural differential networks (ICSDNs) were constructed for each patient and multi-site clustering was used to identify psychosis subtypes. Group differences between subtypes in clinical phenotypes and voxel-wise fractional amplitude of low frequency fluctuation (fALFF) were calculated, as well as between the corresponding relatives.

RESULTS

Two psychosis subtypes were identified with increased whole brain structural covariance, with decreased connectivity between amygdala-hippocampus and temporal-occipital cortex in subtype I (S-I) compared to subtype II (S-II), which was replicated under different clustering methods, number of edges and across datasets (B-SNIP II) and different brain atlases. S-I had higher emotional-related symptoms than S-II and showed significant fALFF decrease in temporal and occipital cortex, while S-II was more similar to HC. This pattern was consistently validated on relatives of S-I and S-II in both fALFF and clinical symptoms.

CONCLUSIONS

These findings reconcile categorical and dimensional perspectives of psychosis neurobiological heterogeneity, indicating that relatives of S-I might have greater predisposition in developing psychosis, while relatives of S-II are more likely to be healthy. This study contributes to the development of neuroimaging informed diagnostic classifications within psychosis spectrum.

Prepulse inhibition deficit as a transdiagnostic process in neuropsychiatric disorders: a systematic review

BACKGROUND

Psychopathological research is moving from a specific approach towards transdiagnosis through the analysis of processes that appear transversally to multiple pathologies. A phenomenon disrupted in several disorders is prepulse inhibition (PPI) of the startle response, in which startle to an intense sensory stimulus, or pulse, is reduced if a weak stimulus, or prepulse, is previously presented.

OBJECTIVE AND METHODS

The present systematic review analyzed the role of PPI deficit as a possible transdiagnostic process for four main groups of neuropsychiatric disorders: (1) trauma-, stress-, and anxiety-related disorders (2) mood-related disorders, (3) neurocognitive disorders, and (4) other disorders such as obsessive-compulsive, tic-related, and substance use disorders. We used Web of Science, PubMed and PsycInfo databases to search for experimental case-control articles that were analyzed both qualitatively and based on their potential risk of bias. A total of 64 studies were included in this systematic review. Protocol was submitted prospectively to PROSPERO 04/30/2022 (CRD42022322031).

RESULTS AND CONCLUSION

The results showed a general PPI deficit in the diagnostic groups mentioned, with associated deficits in the dopaminergic neurotransmission system, several areas implied such as the medial prefrontal cortex or the amygdala, and related variables such as cognitive deficits and anxiety symptoms. It can be concluded that the PPI deficit appears across most of the neuropsychiatric disorders examined, and it could be considered as a relevant measure in translational research for the early detection of such disorders.

Deep psychophysiological phenotyping of adolescents and adults with 22q11.2 deletion syndrome: a multilevel approach to defining core disease processes

BACKGROUND

22q11.2 deletion syndrome (22q11.2DS) is the most common chromosomal interstitial-deletion disorder, occurring in approximately 1 in 2000 to 6000 live births. Affected individuals exhibit variable clinical phenotypes that can include velopharyngeal anomalies, heart defects, T-cell-related immune deficits, dysmorphic facial features, neurodevelopmental disorders, including autism, early cognitive decline, schizophrenia, and other psychiatric disorders. Developing comprehensive treatments for 22q11.2DS requires an understanding of both the psychophysiological and neural mechanisms driving clinical outcomes. Our project probes the core psychophysiological abnormalities of 22q11.2DS in parallel with molecular studies of stem cell-derived neurons to unravel the basic mechanisms and pathophysiology of 22q11.2-related psychiatric disorders, with a primary focus on psychotic disorders. Our study is guided by the central hypothesis that abnormal neural processing associates with psychophysiological processing and underlies clinical diagnosis and symptomatology. Here, we present the scientific background and justification for our study, sharing details of our study design and human data collection protocol.

METHODS

Our study is recruiting individuals with 22q11.2DS and healthy comparison subjects between the ages of 16 and 60 years. We are employing an extensive psychophysiological assessment battery (e.g., EEG, evoked potential measures, and acoustic startle) to assess fundamental sensory detection, attention, and reactivity. To complement these unbiased measures of cognitive processing, we will develop stem-cell derived neurons and examine neuronal phenotypes relevant to neurotransmission. Clinical characterization of our 22q11.2DS and control participants relies on diagnostic and research domain criteria assessments, including standard Axis-I diagnostic and neurocognitive measures, following from the Measurement and Treatment Research to Improve Cognition in Schizophrenia (MATRICS) and the North American Prodrome Longitudinal Study (NAPLS) batteries. We are also collecting measures of autism spectrum (ASD) and attention deficit/hyperactivity disorder (ADHD)-related symptoms.

DISCUSSION

Studying 22q11.2DS in adolescence and adulthood via deep phenotyping across multiple clinical and biological domains may significantly increase our knowledge of its core disease processes. Our manuscript describes our ongoing study's protocol in detail. These paradigms could be adapted by clinical researchers studying 22q11.2DS, other CNV/single gene disorders, or idiopathic psychiatric syndromes, as well as by basic researchers who plan to incorporate biobehavioral outcome measures into their studies of 22q11.2DS.

Clonidine augmentation in patients with schizophrenia: A double-blind, randomized placebo-controlled trial

INTRODUCTION

Noradrenergic imbalance in the brain of schizophrenia patients may underlie both symptomatology and deficits in basic information processing. The current study investigated whether augmentation with the noradrenergic α2-agonist clonidine might alleviate these symptoms.

METHODS

In a double-blind placebo-controlled randomized clinical trial, 32 chronic schizophrenia patients were randomly assigned to six-weeks augmentation with either 50 μg clonidine or placebo to their current medication. Effects on symptom severity and both sensory- and sensorimotor gating were assessed at baseline, 3- and 6-weeks. Results were compared with 21 age- and sex-matched healthy controls (HC) who received no treatment.

RESULTS

Only patients treated with clonidine showed significantly reduced PANSS negative, general and total scores at follow-up compared to baseline. On average, also patients treated with placebo showed minor (non-significant) reductions in these scores, likely indicating a placebo effect. Sensorimotor gating of patients was significantly lower at baseline compared to controls. It increased in patients treated with clonidine over the treatment period, whereas it decreased in both the HC and patients treated with placebo. However, neither treatment nor group effects were found in sensory gating. Clonidine treatment was very well tolerated.

CONCLUSION

Only patients treated with clonidine showed a significant decrease on two out of the three PANSS subscales, while additionally retained their levels of sensorimotor gating. Given that there are only a few reports on effective treatment for negative symptoms in particular, our current results support augmentation of antipsychotics with clonidine as a promising, low-cost and safe treatment strategy for schizophrenia.

P50 inhibition defects, psychopathology and gray matter volume in patients with first-episode drug-naive schizophrenia

BACKGROUND

Sensory gating deficits and gray matter volume (GMV) abnormalities have been found to be associated with the pathogenesis and psychopathology of patients with schizophrenia (SCZ). However, no studies have investigated their interrelationship in first-episode treatment-naive (FETN) SCZ patients.

METHODS

We recruited 52 FETN SCZ patients and 57 healthy controls. The Positive and Negative Syndrome Scale (PANSS) was used to measure the psychopathology of the patients. We collected magnetic resonance imaging and P50 inhibition data from all participants.

RESULTS

Compared to healthy controls, patients had shorter S1 and S2 latencies but larger S2 amplitudes and P50 ratio (Bonferroni adjusted all p < 0.01). In patients, S2 latency was independently associated with PANSS total score, negative symptoms and general psychopathology (t = 2.26-2.58, both P < 0.05), whereas S1 (t = 2.44, P < 0.05) and S2 latencies (t = 2.13, P < 0.05) were associated with PANSS cognitive factor. Moreover, GMV in the left inferior temporal gyrus, left lingual gyrus and right superior occipital gyrus, and bilateral dorsolateral superior frontal gyrus were each associated with the P50 components (all p < 0.05). In addition, GMV associated with S2 latency was negatively correlated with PANSS general psychopathology (t = -2.46, p < 0.05) and total score (t = -2.34, p < 0.05).

CONCLUSIONS

Our findings indicate that FETN SCZ patients exhibit deficits in P50 inhibition and GMV of brain regions associated with these deficits may be associated with their psychopathological symptoms, suggesting that brain structures associated with P50 components may be important biomarkers of SCZ psychopathology. Future studies could use a prospective longitudinal design to investigate the potential causal relationship of brain structures associated with P50 components in the psychopathological symptoms of SCZ patients.

Detection of Schizophrenia Cases From Healthy Controls With Combination of Neurocognitive and Electrophysiological Features

BACKGROUND

The search for a method that utilizes biomarkers to identify patients with schizophrenia from healthy individuals has occupied researchers for decades. However, no single indicator can be employed to achieve the good in clinical practice. We aim to develop a comprehensive machine learning pipeline based on neurocognitive and electrophysiological combined features for distinguishing schizophrenia patients from healthy people.

METHODS

In the present study, 69 patients with schizophrenia and 50 healthy controls participated. Neurocognitive (contains seven specific domains of cognition) and electrophysiological [prepulse inhibition, electroencephalography (EEG) power spectrum, detrended fluctuation analysis, and fractal dimension (FD)] features were collected, all these features were taken together to generate the identification models of schizophrenia by applying logistics, random forest, and extreme gradient boosting algorithm. The classification capabilities of these models were also evaluated.

RESULTS

Both the neurocognitive and electrophysiological feature sets showed a good classification effect with the highest accuracy greater than 85% and AUC greater than 90%. Specifically, the performances of the combined neurocognitive and electrophysiological feature sets achieved the highest accuracy of 93.28% and AUC of 97.91%. The extreme gradient boosting algorithm as a whole presented more stably and precisely in classification efficiency.

CONCLUSION

The highest classification accuracy of 93.28% by combination of neurocognitive and electrophysiological features shows that both measurements are appropriate indicators to be used in discriminating schizophrenia patients and healthy individuals. Also, among three algorithms, extreme gradient boosting had better classified performances than logistics and random forest algorithms.

Prepulse inhibition in first-degree relatives of schizophrenia patients: A systematic review

BACKGROUND

Prepulse inhibition (PPI) is a measure of sensorimotor gating used to identify deficits in early-stage information processing and inhibitory function defects. Many studies support the presence of PPI deficits in schizophrenia patients. However, very few studies have explored PPI levels among first-degree relatives (FDR) of schizophrenia patients, and the results have been inconsistent. This review article explored PPI levels in FDR of schizophrenia patients.

METHODS

We performed a systematic literature review using the PubMed, Cochrane, Embase, EBSCO and Chinese databases from inception to January 2020. A series of related factors (eg, PPI paradigm, heritability and sample characteristics) and outcomes were summarized from the literature that met the inclusion criteria. The Newcastle-Ottawa Scale was used to assess the quality of the included studies.

RESULTS

A total of eight studies were eligible for systematic review after screening. A meta-analysis of the selected studies was not conducted due to the limitations of quantity and paradigm heterogeneity. A majority of the studies' subjects were siblings of schizophrenia patients and different paradigms were applied. Most of the included studies reported no difference in PPI values between FDR of schizophrenia patients and healthy controls.

CONCLUSION

Contrary to traditional certainty that unaffected FDR of schizophrenia patients have PPI defects, our review found no sufficient evidence supporting that the PPI level in FDR of schizophrenia patients was lower than in healthy controls. A prospective cohort study focusing on different outcomes such as developing schizophrenia is required to explore PPI levels in FDR of schizophrenia patients.

Toxoplasma gondii Effects on the Relationship of Kynurenine Pathway Metabolites to Acoustic Startle Latency in Schizophrenia vs. Control Subjects

Background: Chronic infection with Toxoplasma gondii (TOXO) results in microcysts in the brain that are controlled by inflammatory activation and subsequent changes in the kynurenine pathway. TOXO seropositivity is associated with a heightened risk of schizophrenia (SCZ) and with cognitive impairments. Latency of the acoustic startle response, a putative index of neural processing speed, is slower in SCZ. SCZ subjects who are TOXO seropositive have slower latency than SCZ subjects who are TOXO seronegative. We assessed the relationship between kynurenine pathway metabolites and startle latency as a potential route by which chronic TOXO infection can lead to cognitive slowing in SCZ. Methods: Fourty-seven SCZ subjects and 30 controls (CON) were tested on a standard acoustic startle paradigm. Kynurenine pathway metabolites were measured using liquid chromatography-tandem mass spectrometry were kynurenine (KYN), tryptophan (TRYP), 3-hydroxyanthranilic acid (3-OHAA), anthranilic acid (AA), and kynurenic acid (KYNA). TOXO status was determined by IgG ELISA. Results: In univariate ANCOVAs on onset and peak latency with age and log transformed startle magnitude as covariates, both onset latency [F(1,61) = 5.76; p = 0.019] and peak latency [F(1,61) = 4.34; p = 0.041] were slower in SCZ than CON subjects. In stepwise backward linear regressions after stratification by Diagnosis, slower onset latency in SCZ subjects was predicted by higher TRYP (B = 0.42; p = 0.008) and 3-OHAA:AA (B = 3.68; p = 0.007), and lower KYN:TRYP (B = -185.42; p = 0.034). In regressions with peak latency as the dependent variable, slower peak latency was predicted by higher TRYP (B = 0.47; p = 0.013) and 3-OHAA:AA ratio (B = 4.35; p = 0.010), and by lower KYNA (B = -6.67; p = 0.036). In CON subjects neither onset nor peak latency was predicted by any KYN metabolites. In regressions stratified by TOXO status, in TOXO positive subjects, slower peak latency was predicted by lower concentrations of KYN (B = -8.08; p = 0.008), KYNA (B = -10.64; p = 0.003), and lower KYN:TRYP ratios (B = -347.01; p = 0.03). In TOXO negative subjects neither onset nor peak latency was predicted by any KYN metabolites. Conclusions: KYN pathway markers predict slowing of startle latency in SCZ subjects and in those with chronic TOXO infection, but this is not seen in CON subjects nor TOXO seronegative subjects. These findings coupled with prior work indicating a relationship of slower latency with SCZ and TOXO infection suggest that alterations in KYN pathway markers may be a mechanism by which neural processing speed, as indexed by startle latency, is affected in these subjects.

Heritability of acoustic startle magnitude and latency from the consortium on the genetics of schizophrenia

BACKGROUND

Latency of the acoustic startle reflex is the time from presentation of the startling stimulus until the response, and provides an index of neural processing speed. Schizophrenia subjects exhibit slowed latency compared to healthy controls. One prior publication reported significant heritability of latency. The current study was undertaken to replicate and extend this solitary finding in a larger cohort.

METHODS

Schizophrenia probands, their relatives, and control subjects from the Consortium on the Genetics of Schizophrenia (COGS-1) were tested in a paradigm to ascertain magnitude, latency, and prepulse inhibition of startle. Trial types in the paradigm were: pulse-alone, and trials with 30, 60, or 120 ms between the prepulse and pulse. Comparisons of subject groups were conducted with ANCOVAs to assess startle latency and magnitude. Heritability of startle magnitude and latency was analyzed with a variance component method implemented in SOLAR v.4.3.1.

RESULTS

980 subjects had analyzable startle results: 199 schizophrenia probands, 456 of their relatives, and 325 controls. A mixed-design ANCOVA on startle latency in the four trial types was significant for subject group (F(2,973) = 4.45, p = 0.012) such that probands were slowest, relatives were intermediate and controls were fastest. Magnitude to pulse-alone trials differed significantly between groups by ANCOVA (F(2,974) = 3.92, p = 0.020) such that controls were lowest, probands highest, and relatives intermediate. Heritability was significant (p < 0.0001), with heritability of 34-41% for latency and 45-59% for magnitude.

CONCLUSION

Both startle latency and magnitude are significantly heritable in the COGS-1 cohort. Startle latency is a strong candidate for being an endophenotype in schizophrenia.

Evidence of Slow Neural Processing, Developmental Differences and Sensitivity to Cannabis Effects in a Sample at Clinical High Risk for Psychosis From the NAPLS Consortium Assessed With the Human Startle Paradigm

ABSTRACT

Biomarkers are important in the study of the prodromal period of psychosis because they can help to identify individuals at greatest risk for future psychotic illness and provide insights into disease mechanism underlying neurodevelopmental abnormalities. The biomarker abnormalities can then be targeted with treatment, with an aim toward prevention or mitigation of disease. The human startle paradigm has been used in translational studies of psychopathology including psychotic illness to assess preattentive information processing for over 50 years. In one of the largest studies to date in clinical high risk (CHR) for psychosis participants, we aimed to evaluate startle indices as biomarkers of risk along with the role of age, sex, treatment, and substance use in this population of high risk individuals.

METHODS

Startle response reactivity, latency, and prepulse inhibition (PPI) were assessed in 543 CHR and 218 Normal Comparison (NC) participants between the ages of 12 and 35.

RESULTS

At 1 year follow-up, 58 CHR participants had converted to psychosis. CHR and NC groups did not differ across any of the startle measures but those CHR participants who later converted to psychosis had significantly slower startle latency than did those who did not convert to psychosis, and this effect was driven by female CHR participants. PPI was significantly associated with age in the CHR, but not the NC, participants with the greatest positive age correlations present in those CHR participants who later converted to psychosis, consistent with a prior report. Finally, there was a significant group by cannabis use interaction due to greater PPI in cannabis users and opposite PPI group effects in users (CHR>NC) and non-users (NC>CHR).

DISCUSSION

This is the first study to demonstrate a relationship of startle response latency to psychotic conversion in a CHR population. PPI is an important biomarker that may be sensitive to the neurodevelopmental abnormalities thought to be present in psychosis prone individuals and the effects of cannabis. The significant correlations with age in this sample as well as the finding of greater PPI in CHR cannabis users replicate findings from another large sample of CHR participants.