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Several studies have suggested that atypical social processing in multiple psychiatric conditions (e.g., autism) is associated with differences in excitation and inhibition, through changes in the levels of glutamate and GABA levels. While associations between baseline metabolite levels and behaviours can be insightful, assessing the neurometabolic response of GABA and Glutamate during social processing may inform altered neurochemical function in more depth. Thus far, there have been no attempts to determine whether changes in metabolite levels are detectable using functional magnetic resonance spectroscopy (fMRS) during social processing in a control population. We performed MEGA-PRESS edited fMRS to measure the dynamic response of GABA and glutamate in the superior temporal sulcus (STS) and visual cortex (V1) while viewing social stimuli, using a design that allows for analysis in both block and event-related approaches. Sliding window analyses were used to investigate GABA and glutamate dynamics at higher temporal resolution. A small decrease in GABA levels was observed during social stimulus presentation in V1, but no change was observed in STS. Conversely, non-social stimulus elicited changes in both GABA and glutamate levels in both regions. We discuss the feasibility of using fMRS analysis approaches to assess changes in metabolite response during social processing.

IntroductionThere are no well-established biomedical treatments for the core symptoms of autism spectrum disorder (ASD). A small number of studies suggest that repetitive transcranial magnetic stimulation (rTMS), a non-invasive brain stimulation technique, may improve clinical and cognitive outcomes in ASD. We describe here the protocol for a funded multicentre randomised controlled clinical trial to investigate whether a course of rTMS to the right temporoparietal junction (rTPJ), which has demonstrated abnormal brain activation in ASD, can improve social communication in adolescents and young adults with ASD.Methods and analysisThis study will evaluate the safety and efficacy of a 4-week course of intermittent theta burst stimulation (iTBS, a variant of rTMS) in ASD. Participants meeting criteria for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition ASD (n=150, aged 14–40 years) will receive 20 sessions of either active iTBS (600 pulses) or sham iTBS (in which a sham coil mimics the sensation of iTBS, but no active stimulation is delivered) to the rTPJ. Participants will undergo a range of clinical, cognitive, epi/genetic, and neurophysiological assessments before and at multiple time points up to 6 months after iTBS. Safety will be assessed via a structured questionnaire and adverse event reporting. The study will be conducted from November 2020 to October 2024.Ethics and disseminationThe study was approved by the Human Research Ethics Committee of Monash Health (Melbourne, Australia) under Australia’s National Mutual Acceptance scheme. The trial will be conducted according to Good Clinical Practice, and findings will be written up for scholarly publication.Trial registration numberAustralian New Zealand Clinical Trials Registry (ACTRN12620000890932).

Continued human and animal research has strengthened evidence for aberrant excitatory–inhibitory neural processes underlying autism and schizophrenia spectrum disorder psychopathology, particularly psychosocial functioning, in clinical and nonclinical populations. We investigated the extent to which autistic traits and schizotypal dimensions were modulated by the interactive relationship between excitatory glutamate and inhibitory GABA neurotransmitter concentrations in the social processing area of the superior temporal cortex using proton magnetic resonance spectroscopy. In total, 38 non-clinical participants (20 females; age range = 18–35 years, mean (standard deviation) = 23.22 (5.52)) completed the autism spectrum quotient and schizotypal personality questionnaire, and underwent proton magnetic resonance spectroscopy to quantify glutamate and GABA concentrations in the right and left superior temporal cortex. Regression analyses revealed that glutamate and GABA interactively modulated autistic social skills and schizotypal interpersonal features ( pcorr < 0.05), such that those with high right superior temporal cortex glutamate but low GABA concentrations exhibited poorer social and interpersonal skills. These findings evidence an excitation–inhibition imbalance that is specific to psychosocial features across the autism and schizophrenia spectra.

Identifying the factors that drive environmentalism is critical to reduce human impact on the environment. Emotional intelligence (EI) has been shown to influence pro-environmental behaviour and environmental attitudes in adults, while such influences in adolescents are yet to be examined. The current study investigated the relationship between self-reported EI, pro-environmental attitude (PEA) and pro-environmental behaviour (PEB) in 382 Australian adolescents (12–17 years). Higher PEB was associated with higher PEA, and EI dimensions of Emotional Management and Control (EMC), and Understanding Others Emotions (UEO). Hierarchical multiple regression confirmed that PEA predicted PEB, while EMC also predicted PEB. EMC and UEO interactively moderated the relationship between PEA and PEB. This study suggests that adolescents' ability to manage, control and understand emotions affects the extent to which their PEAs predict PEBs, which has significant implications for the development of future environmental education initiatives to encourage pro-environmentalism.

ObjectiveSensory deficits are a feature of autism and schizophrenia, as well as the upper end of their non-clinical spectra. The mismatch negativity (MMN), an index of pre-attentive auditory processing, is particularly sensitive in detecting such deficits; however, little is known about the relationship between the visual MMN (vMMN) to emotional faces and autism and schizophrenia spectrum symptom domains.MethodsWe probed the vMMN to happy, sad, and neutral faces in 77 young adults (18-40 years, 41 female), and evaluated their degree of autism and schizophrenia spectrum traits using the Autism Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire (SPQ). Results: The vMMN to happy faces was significantly larger than the vMMNs to sad and neutral faces (p > 0.05). The vMMN to happy faces was associated with interpersonal difficulties as indexed by AQ Communication and Attention to Detail subscales, and SPQ Interpersonal Features (p < 0.05, uncorrected), such that a larger vMMN was associated with more interpersonal difficulties.ConclusionsPre-attentive processing of positive affect might be more specific to the interpersonal features associated with autism and schizophrenia.SignificanceThese findings add valuable insights into the growing body of literature investigating symptom-specific neurobiological markers of autism and schizophrenia spectrum conditions.Highlights-The visual Mismatch Negativity (vMMN) is larger in response to happy compared to sad or neutral facial expressions-The vMMN to happy facial expressions is specifically associated with more social communication difficulties-vMMN to positive affect may be a neural mechanism associated with social communication difficulties in autism and schizophrenia

In many communities, cannabis is perceived as a low-risk drug, leading to political lobbying to decriminalise its use. Acute and chronic cannabis use has been shown to be harmful to several aspects of psychological and physical health, such as mood states, psychiatric outcomes, neurocognition, driving and general health. Furthermore, cannabis is highly addictive, and the adverse effects of withdrawal can lead to regular use. These in turn have adverse implications for public safety and health expenditure. Although the cannabinoid cannabidiol (CBD) has been shown to have positive health outcomes with its antioxidant, anticonvulsant, anti-inflammatory and neuroprotective properties, high-potency cannabis is particularly damaging due to its high tetrahydrocannabinol (THC), low CDB concentration. It is this high-potency substance that is readily available recreationally. While pharmaceutical initiatives continue to investigate the medical benefits of CDB, "medicinal cannabis" still contains damaging levels of THC. Altogether, we argue there is insufficient evidence to support the safety of cannabis and its subsequent legalisation for recreational use. Furthermore, its use for medicinal purposes should be done with care. We argue that the public conversation for the legalisation of cannabis must include scientific evidence for its adverse effects.

Auditory processing deficits are frequently identified in autism and schizophrenia, and the two disorders have been shown to share psychosocial difficulties. This study used magnetoencephalography to investigate auditory processing differences for those with a high degree of a non-clinical autistic and schizotypal trait phenotype, Social Disorganisation (SD). Participants were 18 low (9 female) and 19 high (9 female) SD scorers (18-40 years) who completed a three-stimulus auditory oddball paradigm of speech sounds (standard: 100ms 'o', deviant: 150ms 'o', novel: 150ms 'e'). Spatio-temporal cluster analysis revealed increased amplitude for the high SD group in a left (p = 0.006) and a right (p = 0.020) hemisphere cluster in response to the novel non-target. No cluster differences were found in response to the target deviant. These findings suggest that those with a high degree of the SD phenotype recruit more cortical resources when processing unattended, novel speech stimuli, which may lead to psychosocial deficits.

Background Risky driving is considered a key predictive factor in road traffic accidents resulting in morbidity and mortality. Intra-individual emotional and personality factors have been shown to influence risk-taking behaviours among drivers. Despite this, there is limited research investigating the individual dimensions of these constructs and their relationship to risky driving behaviour (RDB). The current study therefore aimed to assess whether the individual dimensions of Emotional Intelligence (EI) were implicated in RDB. Methods The sample comprised 179 adults (55% male) aged between 18 and 64 years (M = 29.85, SD = 11.46) and who currently held a valid driver’s licence completed an online survey. Emotional Intelligence was assessed via self-report using the Swinburne University Emotional Intelligence Test (SUEIT), and RDB was measured using both the Brief Distracted Driving Scale (BDDS) and the Dula Dangerous Driving Index (DDDI). Results Regression analyses revealed that ‘Risky Driving’ was related to greater levels of Emotional Recognition and Expression and lesser Age [F(6, 172) = 2.27, p Conclusions Lower scores on specific indices of EI are associated with increased rates of RDB, suggesting that poor emotional control may impede an individuals’ ability to make safe behavioural decisions when driving. The effect sizes for these models were small, however, and further research is needed to explore the contributory components in this association. Greater awareness of the role of emotional regulation and driving behaviours may be useful in preventing RDB in adults.

The relationship between the Autism Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire (SPQ) data has consistently shown overlap in the social and interpersonal domains. Factor analyses of the AQ and SPQ subscales support this overlap with the emergence of a shared AQ and SPQ subscale factor as the largest common element. This study investigated, at the item level, the factor structure of the AQ and SPQ. Exploratory and confirmatory factor analyses were conducted on the AQ and SPQ responses of 1670 participants (aged 18–40, 1243 females, 427 males). Seven factors cumulatively explained 40.56% of the data. Of these, four represented shared traits (named Odd Behaviour, Relationship Disinterest, Cue Interpretation, Social and Communication Discomfort), one was a more specific autistic tendency (named Fixation with Details), and two factors were more specific to the psychotic dimension of schizotypy (named Paranoia/Suspiciousness and Hallucination/Delusional Experiences). These findings demonstrate that a set of symptom traits is present in both the autism and schizophrenia spectra. The findings of this study have important clinical implications in terms of future research, diagnosis and treatment of autism and schizophrenia spectrum disorders.

The recreational use of various stimulant drugs has been implicated in the development of movement disorders through dysregulation of the dopaminergic and serotoninergic neurotransmitter systems. The present study investigated psychomotor differences in current and former recreational stimulant drug users compared with nonusing controls. Sixty participants comprised 3 groups: 20 current stimulant drug users (CSUs; 11 men, aged 31.4 ± 9.1 years), 20 former stimulant drug users (FSUs; 5 men, aged 39.1 ± 8.5 years), and 20 nonuser controls (NUCs; 5 men, aged 35.7 ± 6.4 years). Psychomotor arm steadiness for each participant was assessed with a wrist-attached accelerometer during 5 arm positions with eyes open and then eyes closed. Arm-drop of arm position was indicated by the arm longitudinal rotation axis (ALoRA), and tremor was indicated by the overall vector of dynamic body acceleration (VeDBA). Overall, CSUs performed the most poorly on ALoRA (P < .05) and VeDBA indices (P < .05), and FSUs perform almost as poorly on VeDBA indices (P < .05) compared with NUCs. It was concluded that stimulant drug use, primarily MDMA and amphetamines, may result in acute stimulant-induced tremor as well as long-term proprioceptive deficits in terms of arm-droop.

Social Disorganisation (SD) is a shared autistic and schizotypal phenotype that is present in the subclinical population. Auditory processing deficits, particularly in mismatch negativity/field (MMN/F) have been reported across both spectrum disorders. This study investigates differences in MMN/F cortical spatio-temporal source activity between higher and lower quintiles of the SD spectrum. Sixteen low (9 female) and 19 high (9 female) SD subclinical adults (18–40years) underwent magnetoencephalography (MEG) during an MMF paradigm where standard tones (50ms) were interrupted by infrequent duration deviants (100ms). Spatio-temporal source cluster analysis with permutation testing revealed no difference between the groups in source activation to the standard tone. To the deviant tone however, there was significantly reduced right hemisphere fronto-temporal and insular cortex activation for the high SD group (p= 0.038). The MMF, as a product of the cortical response to the deviant minus that to the standard, did not differ significantly between the high and low Social Disorganisation groups. These data demonstrate a deficit in right fronto-temporal processing of an auditory change for those with more of the shared SD phenotype, indicating that right fronto-temporal auditory processing may be associated with psychosocial functioning., Highlights • Autism and schizotypal spectra share a trait phenotype, Social Disorganisation (SD). • Auditory mismatch paradigm demonstrates processing differences between high and low SD. • High SD scorers have reduced fronto-temporal response to auditory change. • Reduced fronto-temporal source activation in high SD is right lateralised. • Psychosocial function is related to auditory deviant processing.

Autism and schizophrenia are multi-dimensional spectrum disorders that have substantial phenotypic overlap. This overlap is readily identified in the non-clinical population, and has been conceptualised as Social Disorganisation (SD). This study investigates the balance of excitatory glutamate and inhibitory γ-aminobutyric acid (GABA) concentrations in a non-clinical sample with high and low trait SD, as glutamate and GABA abnormalities are reported across the autism and schizophrenia spectrum disorders.Participants were 18 low (10 females) and 19 high (9 females) SD scorers aged 18 to 40years who underwent 1H-MRS for glutamate and GABA+macromolecule (GABA+) concentrations in right and left hemisphere superior temporal (ST) voxels.Reduced GABA+ concentration (p=0.03) and increased glutamate/GABA+ ratio (p=0.003) in the right ST voxel for the high SD group was found, and there was increased GABA+ concentration in the left compared to right ST voxel (p=0.047). Bilateral glutamate concentration was increased for the high SD group (p=0.006); there was no hemisphere by group interaction (p=0.772).Results suggest that a higher expression of the SD phenotype may be associated with increased glutamate/GABA+ ratio in the right ST region, which may affect speech prosody processing, and lead behavioural characteristics that are shared within the autistic and schizotypal spectra. Keywords: 1H-MRS, Glutmate, GABA, Autism, Schizophrenia, Social Disorganisation

Several lines of evidence identify aberrant excitatory-inhibitory neural processes across autism and schizophrenia spectrum disorders, particularly within the psychosocial domain. Such neural processes include increased excitatory glutamate and reduced inhibitory GABA concentrations, which may affect auditory pre-attentive processing as indexed by the mismatch negativity (MMN); thus, an excitation-inhibition imbalance might lead to aberrant MMN, which might in turn drive the relationship between the MMN and psychosocial difficulties. This research has the potential to enhance the neurochemical understanding of the relationship between electrophysiology (MMN) and behavioural/clinical measures (psychosocial difficulties).Thirty-eight adults (18 male, 18-40 years) completed the Schizotypal Personality Questionnaire (SPQ) and Autism-Spectrum Quotient (AQ). Glutamate and GABA concentrations in bilateral superior temporal cortex (STC) were quantified using proton magnetic resonance spectroscopy (1H-MRS) while auditory MMN to a duration deviant was measured with magnetoencephalography. Spearman correlations probed the relationships between STC glutamate/GABA ratios, MMN amplitude and latency, and AQ and SPQ dimensions. Mediation effects of glutamate/GABA ratios on the relationship between MMN and AQ-SPQ dimensions were probed using causal mediation analysis.Only SPQ-interpersonal and AQ-communication were significantly correlated with right hemisphere glutamate/GABA ratios and MMN latency (psp=.038). Two mediation models were investigated, with right MMN latency as predictor and SPQ-interpersonal and AQ-communication as outcome variables. Right STC glutamate/GABA ratios significantly mediated the relationship between MMN latency and SPQ-interpersonal scores (ß=86.6, p=.033), but only partially mediated the relationship between MMN latency and AQ-communication scores (ß=21.0, p=.093).These findings support the growing body of literature pointing toward an excitation-inhibition imbalance that is central to psychosocial functioning across multi-dimensional spectrum disorders, such as autism and schizophrenia, and provides neurochemical indicators of the processes that underlie psychosocial dysfunction.

Individuals with autism and those with high subclinical autistic traits often report poor trait emotional intelligence (EI) and psychosocial outcomes. EI predicts resiliency in adolescents, however, the interrelationship between autistic traits, EI and resiliency is unknown. The Adolescent Swinburne University EI Test, Autism-Spectrum Quotient (AQ) and Resiliency Scales for Children and Adolescents were completed by 212 adolescents (193 males; 14–17 years). In line with previous studies, adolescents with better EI reported more resiliency, and fewer autistic traits, while fewer autistic traits were associated with better resiliency. Mediation analyses revealed that the relationships between EI dimensions and resiliency were partially or fully mediated by AQ Social Skills and AQ Communication, suggesting that trait EI is an important predictor of resiliency, but that these autistic trait dimensions drive this relationship. The findings have significant implications for developing EI programs that foster resiliency in adolescents across the clinical and subclinical autism spectrum.

Several lines of evidence identify aberrant excitatory-inhibitory neural processes across autism and schizophrenia spectrum disorders, particularly within the psychosocial domain. Such neural processes include increased excitatory glutamate and reduced inhibitory GABA concentrations, which may affect auditory pre-attentive processing as indexed by the mismatch negativity (MMN); thus, an excitation-inhibition imbalance might lead to aberrant MMN, which might in turn drive the relationship between the MMN and psychosocial difficulties. This research has the potential to enhance the neurochemical understanding of the relationship between electrophysiology (MMN) and behavioural/clinical measures (psychosocial difficulties). Thirty-eight adults (18 male, 18-40 years) completed the Schizotypal Personality Questionnaire (SPQ) and Autism-Spectrum Quotient (AQ). Glutamate and GABA concentrations in bilateral superior temporal cortex (STC) were quantified using proton magnetic resonance spectroscopy (1H-MRS) while auditory MMN to a duration deviant was measured with magnetoencephalography. Spearman correlations probed the relationships between STC glutamate/GABA ratios, MMN amplitude and latency, and AQ and SPQ dimensions. Mediation effects of glutamate/GABA ratios on the relationship between MMN and AQ-SPQ dimensions were probed using causal mediation analysis. Only SPQ-interpersonal and AQ-communication were significantly correlated with right hemisphere glutamate/GABA ratios and MMN latency (ps 0.05), which were themselves correlated (p = .035). Two mediation models were investigated, with right MMN latency as predictor and SPQ-interpersonal and AQ-communication as outcome variables. Right STC glutamate/GABA ratios significantly mediated the relationship between MMN latency and SPQ-interpersonal scores, but only partially mediated the relationship between MMN latency and AQ-communication scores. These findings support the growing body of literature pointing toward an excitation-inhibition imbalance that is central to psychosocial functioning across multi-dimensional spectrum disorders, such as autism and schizophrenia, and provides neurochemical indicators of the processes that underlie psychosocial dysfunction.

A diet rich in B-group vitamins is essential for optimal body and brain function, and insufficient amounts of such vitamins have been associated with higher levels of neural inflammation and oxidative stress, as marked by increased blood plasma homocysteine. Neural biomarkers of oxidative stress quantified through proton magnetic spectroscopy (1H-MRS) are not well understood, and the relationship between such neural and blood biomarkers is seldom studied. The current study addresses this gap by investigating the direct effect of 6-month high-dose B-group vitamin supplementation on neural and blood biomarkers of metabolism. Using a randomized, double-blind, placebo-controlled design, 32 healthy adults (20 female, 12 male) aged 30&ndash, 65 years underwent blood tests (vitamin B6, vitamin B12, folate, and homocysteine levels) and 1H-MRS of the posterior cingulate cortex (PCC) and dorsolateral prefrontal cortex (DLPFC) before and after supplementation. Results confirmed the supplement was effective in increasing vitamin B6 and vitamin B12 levels and reducing homocysteine, whereas there was no change in folate levels. There were significant relationships between vitamin B6 and N-acetylaspartate (NAA), choline, and creatine, as well as between vitamin B12 and creatine (ps &lt, 0.05), whereas NAA in the PCC increased, albeit not significantly (p &gt, 0.05). Together these data provide preliminary evidence for the efficacy of high-dose B-group supplementation in reducing oxidative stress and inflammation through increasing oxidative metabolism. It may also promote myelination, cellular metabolism, and energy storage.

The underlying mechanisms of autism and schizophrenia are poorly understood, partly due to a lack of dimension-specific research. Aberrant excitatory and inhibitory neurotransmission are implicated in both conditions, particularly in social dysfunction. This study investigates the extent to which the degree of autistic tendency and psychosis-proneness exclusively and interactively predict excitatory and inhibitory neurotransmitter concentrations in the superior temporal cortex (STC). In 38 adults (18 male, 18-40 years), we obtained autistic tendencies (Autism-Spectrum Quotient [AQ]) and psychosis-proneness scores (Schizotypal Personality Questionnaire [PP]); magnetic resonance spectroscopy (MRS) quantified glutamate and GABA+ concentrations from the STC. Results demonstrated a negative AQ/PP interaction with glutamate concentration for the left STC voxel, where PP increased with glutamate for average AQ, while AQ decreased with glutamate for average-high PP. There was a negative AQ/PP interaction with glutamate/GABA+ ratio for the right STC, AQ increasing with glutamate/GABA+ for low-average PP, while PP decreased with glutamate/GABA+ for high AQ. Consistent with animal studies, we also reveal that overall reduced glutamate/GABA+ ratio might be precipitated by increased right hemisphere GABA+ concentrations. These findings illustrate the importance of considering the concurrent effects of autism and psychosis dimensions on understanding the pathophysiological mechanisms implicated in either condition, and can advance psychopharmacological research into better treatment options for patients.

Anxiety is associated with compromised cognitive control functions, such as working memory. State and trait anxiety within the non-clinical population can be utilised to investigate potential neural markers for anxiety, which may help to elucidate potential prevention and intervention methods. Thirty-two healthy adults (20 female, 12 male), aged between 30 and 65 years, performed a 2-back task whilst fMRI BOLD signal was acquired using a 3T scanner. Mean BOLD signal was obtained in cognitive control network regions of interest of: left and right dorsolateral prefrontal cortex (DLPFC) and posterior parietal lobe (PPL), and medial prefrontal cortex (MPFC). State and trait anxiety levels were recorded. Higher overall anxiety was moderately associated with more left and right PPL BOLD signal; there was a weak relationship between anxiety and left DLPFC BOLD signal. MPFC BOLD signal and trait anxiety were moderately associated with overall 2-back task performance. These findings suggest that non-clinical anxiety affects the recruitment of cortical resources during working memory, but that anxiety does not impair performance during a 2-back task.

Autism and schizophrenia spectrum research is typically based on coarse diagnostic classification, which overlooks individual variation within clinical groups. This method limits the identification of underlying cognitive, genetic and neural correlates of specific symptom dimensions. This study, therefore, aimed to identify homogenous subclinical subgroups of specific autistic and schizotypal traits dimensions, that may be utilised to establish more effective diagnostic and treatment practices. Latent profile analysis of subscale scores derived from an autism-schizotypy questionnaire, completed by 1678 subclinical adults aged 18–40 years (1250 females), identified a local optimum of eight population clusters: High, Moderate and Low Psychosocial Difficulties; High, Moderate and Low Autism-Schizotypy; High Psychosis-Proneness; and Moderate Schizotypy. These subgroups represent the convergent and discriminant dimensions of autism and schizotypy in the subclinical population, and highlight the importance of examining subgroups of specific symptom characteristics across these spectra in order to identify the underlying genetic and neural correlates that can be utilised to advance diagnostic and treatment practices.

The recreational use of various stimulant drugs has been implicated in the development of movement disorders through dysregulation of the dopaminergic and serotoninergic neurotransmitter systems. The present study investigated psychomotor differences in current and former recreational stimulant drug users compared with nonusing controls. Sixty participants comprised 3 groups: 20 current stimulant drug users (CSUs; 11 men, aged 31.4 ± 9.1 years), 20 former stimulant drug users (FSUs; 5 men, aged 39.1 ± 8.5 years), and 20 nonuser controls (NUCs; 5 men, aged 35.7 ± 6.4 years). Psychomotor arm steadiness for each participant was assessed with a wrist-attached accelerometer during 5 arm positions with eyes open and then eyes closed. Arm-drop of arm position was indicated by the arm longitudinal rotation axis (ALoRA), and tremor was indicated by the overall vector of dynamic body acceleration (VeDBA). Overall, CSUs performed the most poorly on ALoRA (P.05) and VeDBA indices (P.05), and FSUs perform almost as poorly on VeDBA indices (P.05) compared with NUCs. It was concluded that stimulant drug use, primarily MDMA and amphetamines, may result in acute stimulant-induced tremor as well as long-term proprioceptive deficits in terms of arm-droop.

BACKGROUND: The autism and schizophrenia spectra overlap to a large degree in the social and interpersonal domains. Similarly, abnormal excitatory glutamate and inhibitory γ-aminobutyric acid (GABA) neurotransmitter concentrations have been reported for both spectra, with the interplay of these neurotransmitters important for cortical excitation to inhibition regulation. This study investigates whether these neurotransmitter abnormalities are specific to the shared symptomatology, and whether the degree of abnormality increases with increasing symptom severity. Hence, the relationship between the glutamate/GABA ratio and autism and schizophrenia spectrum traits in an unmedicated, subclinical population was investigated. METHODS: A total of 37 adults (19 female, 18 male) aged 18-38 years completed the Autism Spectrum Quotient (AQ) and Schizotypal Personality Questionnaire (SPQ), and participated in the resting state proton magnetic resonance spectroscopy study in which sequences specific for quantification of glutamate and GABA+ concentration were applied to a right and left superior temporal voxel. RESULTS: There were significant, moderate, positive relationships between right superior temporal glutamate/GABA+ ratio and AQ, SPQ and AQ+SPQ total scores (p

The auditory mismatch negativity (MMN), a preattentive processing potential, and its magnetic counterpart (MMF) are consistently reported as reduced in schizophrenia and autism spectrum disorders. This study investigates whether MMF characteristics differ between subclinically high and low scorers on the recently discovered shared autism and schizophrenia phenotype, Social Disorganisation. A total of 18 low (10 females) and 19 high (9 females) Social Disorganisation scorers underwent magnetoencephalography (MEG) during a MMF paradigm of 50ms standard (1000Hz, 85%) and 100ms duration deviant tones. MMF was measured from the strongest active magnetometer over the right and left hemispheres (consistent across groups) after 100ms. No differences in MMF power were found, however there was a significant delay in the MMF peak (p=0.007). The P3am (following the MMF) was significantly reduced across both hemispheres for the high Social Disorganisation group (p=0.025), there were no specific hemispheric differences in P3am power or latency. Right MMF peak latency increased with higher scores on the schizotypal subscales Odd Speech, Odd Behaviour and Constricted Affect. Findings suggest that MMF peak latency delay marks a convergence of the autism and schizophrenia spectra at a subclinical. These findings have significant implications for future research methodology, as well as clinical practice.

Neuroimaging studies of neuropsychiatric behavior biomarkers across spectrum disorders are typically based on diagnosis, thus failing to account for the heterogeneity of multi-dimensional spectrum disorders such as autism (ASD). Control group trait phenotypes are also seldom reported. Proton magnetic resonance spectroscopy ((1)H-MRS) measures the abundance of neurochemicals such as neurotransmitters and metabolites and hence can probe disorder phenotypes at clinical and sub-clinical levels. This detailed review summarizes and critiques the current (1)H-MRS research in ASD. The literature reports reduced N-acetylaspartate (NAA), glutamate and glutamine (Glx), γ-aminobutyric acid (GABA), creatine and choline, and increased glutamate for children with ASD. Adult studies are few and results are inconclusive. Overall, the literature has several limitations arising from differences in (1)H-MRS methodology and sample demographics. We argue that more consistent methods and greater emphasis on phenotype studies will advance understanding of underlying cortical metabolite disturbance in ASD, and the detection, diagnosis, and treatment of ASD and other multi-dimensional psychiatric disorders.

Behavioral and cognitive dysfunction, particularly social and communication impairments, are shared between autism and schizophrenia spectrum disorders, while evidence for a diametric autism-positive schizophrenia symptom profile is inconsistent. We investigated the shared phenotype at a personality trait level, particularly its resemblance to schizoid personality disorder, as well as differential aspects of the autism-schizophrenia model. Items of the autism spectrum quotient (AQ) and schizotypal personality questionnaire (SPQ) were pseudo-randomly combined, and were completed by 449 (162 male, 287 female) non-clinical participants aged 18-40. A factor analysis revealed three factors; the first represented a shared social disorganization phenotype, the second reflected perceptual oddities specific to schizotypy while the third reflected social rigidity specific to autism. The AQ and SPQ were strongly correlated with Factor 1 (AQ: r = 0.75, p