Assessment of olfactory detection thresholds in children with autism spectrum disorders using a pulse ejection system

Parenting behaviors in mice: Olfactory mechanisms and features in models of autism spectrum disorders

Rodents, along with numerous other mammals, heavily depend on olfactory cues to navigate their social interactions. Processing of olfactory sensory inputs is mediated by conserved brain circuits that ultimately trigger social behaviors, such as social interactions and parental care. Although innate, parenting is influenced by internal states, social experience, genetics, and the environment, and any significant disruption of these factors can impact the social circuits. Here, we review the molecular mechanisms and social circuits from the olfactory epithelium to central processing that initiate parental behaviors and their dysregulations that may contribute to the social impairments in mouse models of autism spectrum disorders (ASD). We discuss recent advances of the crucial role of olfaction in parental care, its consequences for social interactions, and the reciprocal influence on social interaction impairments in mouse models of ASD.

Giftedness and atypical sexual differentiation: enhanced perceptual functioning through estrogen deficiency instead of androgen excess

Syndromic autism spectrum conditions (ASC), such as Klinefelter syndrome, also manifest hypogonadism. Compared to the popular Extreme Male Brain theory, the Enhanced Perceptual Functioning model explains the connection between ASC, savant traits, and giftedness more seamlessly, and their co-emergence with atypical sexual differentiation. Overexcitability of primary sensory inputs generates a relative enhancement of local to global processing of stimuli, hindering the abstraction of communication signals, in contrast to the extraordinary local information processing skills in some individuals. Weaker inhibitory function through gamma-aminobutyric acid type A (GABAA) receptors and the atypicality of synapse formation lead to this difference, and the formation of unique neural circuits that process external information. Additionally, deficiency in monitoring inner sensory information leads to alexithymia (inability to distinguish one's own emotions), which can be caused by hypoactivity of estrogen and oxytocin in the interoceptive neural circuits, comprising the anterior insular and cingulate gyri. These areas are also part of the Salience Network, which switches between the Central Executive Network for external tasks and the Default Mode Network for self-referential mind wandering. Exploring the possibility that estrogen deficiency since early development interrupts GABA shift, causing sensory processing atypicality, it helps to evaluate the co-occurrence of ASC with attention deficit hyperactivity disorder, dyslexia, and schizophrenia based on phenotypic and physiological bases. It also provides clues for understanding the common underpinnings of these neurodevelopmental disorders and gifted populations.

Systematic review and meta-analysis: multimodal functional and anatomical neural alterations in autism spectrum disorder

BACKGROUND

This meta-analysis aimed to explore the most robust findings across numerous existing resting-state functional imaging and voxel-based morphometry (VBM) studies on the functional and structural brain alterations in individuals with autism spectrum disorder (ASD).

METHODS

A whole-brain voxel-wise meta-analysis was conducted to compare the differences in the intrinsic functional activity and gray matter volume (GMV) between individuals with ASD and typically developing individuals (TDs) using Seed-based d Mapping software.

RESULTS

A total of 23 functional imaging studies (786 ASD, 710 TDs) and 52 VBM studies (1728 ASD, 1747 TDs) were included. Compared with TDs, individuals with ASD displayed resting-state functional decreases in the left insula (extending to left superior temporal gyrus [STG]), bilateral anterior cingulate cortex/medial prefrontal cortex (ACC/mPFC), left angular gyrus and right inferior temporal gyrus, as well as increases in the right supplementary motor area and precuneus. For VBM meta-analysis, individuals with ASD displayed decreased GMV in the ACC/mPFC and left cerebellum, and increased GMV in the left middle temporal gyrus (extending to the left insula and STG), bilateral olfactory cortex, and right precentral gyrus. Further, individuals with ASD displayed decreased resting-state functional activity and increased GMV in the left insula after overlapping the functional and structural differences.

CONCLUSIONS

The present multimodal meta-analysis demonstrated that ASD exhibited similar alterations in both function and structure of the insula and ACC/mPFC, and functional or structural alterations in the default mode network (DMN), primary motor and sensory regions. These findings contribute to further understanding of the pathophysiology of ASD.

Olfactory Dysfunction in Children: A Scoping Review

OBJECTIVE

Olfactory disorders are well-studied in the adult population, however, there is a paucity of literature characterizing olfactory dysfunction in pediatric patients. The purpose of this scoping review was to identify known causes of olfactory loss in pediatric populations, clarify the extent of use and validity of smell tests, and summarize current therapies for olfactory loss.

DATA SOURCES

PubMed, Ovid MEDLINE, and Web of Science.

REVIEW METHODS

Databases were systematically searched in September 2020. Two independent reviewers conducted the title and abstract screen, followed by review of full-texts for inclusion based on preset inclusion and exclusion criteria. Extracted data included study type, age/age-range of participants, gender, radiological evidence of olfactory dysfunction, types and results of smell tests used, etiology of olfactory loss, and therapies employed for olfactory loss.

RESULTS

A total of 103 articles (n = 1654) were eligible for final data extraction. The University of Pennsylvania Smell Identification Test was used most frequently for smell testing (21% of studies). In total, 45 causes of olfactory dysfunction have been elucidated by this study: 22 congenital and 23 acquired. Few therapies were described, and all were specific to the etiology of olfactory loss.

CONCLUSION

Olfactory dysfunction has a wide range of etiologies in the pediatric population, and clinicians should have a diagnostic algorithm for how to identify a cause should they encounter it in practice. If no etiology can be identified, education around safety should be provided to both the patient and their caregivers.

Disgust Processing and Potential Relationships with Behaviors in Autism

PURPOSE OF REVIEW

While there are reports of differences in emotion processing in autism, it is less understood whether the emotion of disgust, in particular, plays a significant role in these effects. Here, we review literature on potential disgust processing differences in autism and its possible associations with autistic traits.

RECENT FINDINGS

In autism, there is evidence for differences in physical disgust processing, pica behaviors, attention away from other's disgust facial expressions, and differences in neural activity related to disgust processing. In typically developing individuals, disgust processing is related to moral processing, but modulated by individual differences in interoception and alexithymia. Autistic individuals may experience atypical disgust, which may lead to difficulty avoiding contaminants and affect socio-emotional processing. In autism, such outcomes may lead to increased occurrences of illness, contribute to gastrointestinal issues, diminish vicarious learning of disgust expression and behaviors, and potentially contribute to differences in processes related to moral reasoning, though further research is needed.

Repeated exposure to kairomone-containing coffee odor improves abnormal olfactory behaviors in heterozygous oxytocin receptor knock-in mice

The oxytocin receptor (OXTR) knockout mouse is a model of autism spectrum disorder, characterized by abnormalities in social and olfactory behaviors and learning. Previously, we demonstrated that OXTR plays a crucial role in regulating aversive olfactory behavior to butyric acid odor. In this study, we attempted to determine whether coffee aroma affects the abnormal olfactory behavior of OXTR-Venus knock-in heterozygous mice [heterozygous OXTR (±) mice] using a set of behavioral and molecular experiments. Four-week repeated exposures of heterozygous OXTR (±) mice to coffee odor, containing three kairomone alkylpyrazines, rescued the abnormal olfactory behaviors compared with non-exposed wild-type or heterozygous OXTR (±) mice. Increased Oxtr mRNA expression in the olfactory bulb and amygdala coincided with the rescue of abnormal olfactory behaviors. In addition, despite containing the kairomone compounds, both the wild-type and heterozygous OXTR (±) mice exhibited a preference for the coffee odor and exhibited no stress-like increase in the corticotropin-releasing hormone, instead of a kairomone-associated avoidance response. The repeated exposures to the coffee odor did not change oxytocin and estrogen synthetase/receptors as a regulator of the gonadotropic hormone. These data suggest that the rescue of abnormal olfactory behaviors in heterozygous OXTR (±) mice is due to the coffee odor exposure-induced OXTR expression.

Odor identification impairment in autism spectrum disorder might be associated with mitochondrial dysfunction

Deficits in olfactory function in autism spectrum disorder (ASD) have already been reported. However, the results of previous studies are not consistent, and the pathophysiological mechanisms of olfactory dysfunction in ASD are not clear. Fifty-three male ASD children or teenagers aged 9-16 years were recruited for the study. The identification and discrimination portion of the Sniffin' Sticks test (SST) was used to assess the olfactory function of the enrolled subjects. The severity of ASD core symptoms and the intelligence quotient (IQ) of participants were assessed. In addition, to explore the potential mechanism underlying olfactory dysfunction, a series of plasma biochemical indicators of oxidative stress, mitochondrial function and inflammation were measured. The mean raw scores on the SST identification and discrimination test of the study subjects were significantly lower than those of typically developing subjects reported in normative data studies. After adjusting for IQ, the odor identification score was not significantly associated with any ASD symptoms. Odor identification was found to be significantly associated with the ratio of L-lactate (L)/pyruvate (P) but not with other measured indicators. The current study validates the impairment of odor identification and discrimination in Chinese ASD children. Odor identification dysfunction may be an independent clinical symptom of ASD. The plasma L/P ratio was found to be significantly associated with odor identification performance, which suggests that mitochondrial dysfunction may be a potential mechanism underlying odor identification impairment in ASD.

Not Only COVID-19: Involvement of Multiple Chemosensory Systems in Human Diseases

Chemosensory systems are deemed marginal in human pathology. In appraising their role, we aim at suggesting a paradigm shift based on the available clinical and experimental data that will be discussed. Taste and olfaction are polymodal sensory systems, providing inputs to many brain structures that regulate crucial visceral functions, including metabolism but also endocrine, cardiovascular, respiratory, and immune systems. Moreover, other visceral chemosensory systems monitor different essential chemical parameters of “milieu intérieur,” transmitting their data to the brain areas receiving taste and olfactory inputs; hence, they participate in regulating the same vital functions. These chemosensory cells share many molecular features with olfactory or taste receptor cells, thus they may be affected by the same pathological events. In most COVID-19 patients, taste and olfaction are disturbed. This may represent only a small portion of a broadly diffuse chemosensory incapacitation. Indeed, many COVID-19 peculiar symptoms may be explained by the impairment of visceral chemosensory systems, for example, silent hypoxia, diarrhea, and the “cytokine storm”. Dysregulation of chemosensory systems may underlie the much higher mortality rate of COVID-19 Acute Respiratory Distress Syndrome (ARDS) compared to ARDSs of different origins. In chronic non-infectious diseases like hypertension, diabetes, or cancer, the impairment of taste and/or olfaction has been consistently reported. This may signal diffuse chemosensory failure, possibly worsening the prognosis of these patients. Incapacitation of one or few chemosensory systems has negligible effects on survival under ordinary life conditions but, under stress, like metabolic imbalance or COVID-19 pneumonia, the impairment of multiple chemosensory systems may lead to dire consequences during the course of the disease.

A map of assistive technology educative instruments in neurodevelopmental disorders

PURPOSE

The use of assistive technology in mental health has gained an increased interest over the last decades. A growing number of studies have investigated diverse applications of technological interventions for rehabilitation of children with neurodevelopmental disorders. This article presents a map of the technological devises applied as therapeutic instruments.

METHODS

The research question of this review was which technological applications could be referred as an educational instrument for the management of children with autism spectrum disorders (ASDs), intellectual disability and attention deficit disorder. The articles included in this review were collected after a structured literature search in electronic databases using keywords such as "Assistive Technology", "technology devices", "robots", "Autism Disorder", "Intellectual Disabilities" and "Mental Retardation".

RESULTS

Assistive technology with the most up-to-date devices and applications helps children with intellectual disability and ASDs enhance cognitive skills and improve challenging behaviour, social communication and academic performance. Different technological tools are used to foster attention span and improve time management skills in children with attention deficit syndrome.

CONCLUSION

It is important that therapists choose the instrument that will offer the best approach towards the goal that is set. Future research could provide evidence based data, evaluating each specific methodology and tailoring each therapeutic approach specifically to a case.IMPLICATIONS FOR REHABILITATIONTechnology creates environments in which children could practice and learn in a safer, more predictable and pleasant manner.Assistive Technologies provide the opportunity for better acquisition of selfhelp skills and the power of social interaction for individuals with disabilities.By mapping out the wide array of Assistive Technology that is available today, future applications for rehabilitation of children with neurodevelopmental disorders could help extend therapeutic strategies out of the clinical and school settings and into the home, thereby incorporating the family and emphasizing personalization.Future studies could develop a model for the choice and use of each tool, tailoring each therapeutic approach specifically to each case.

Prefrontal Responses to Odors in Individuals With Autism Spectrum Disorders: Functional NIRS Measurement Combined With a Fragrance Pulse Ejection System

Individuals with autism spectrum disorders (ASD) are impaired not only in social competencies but also in sensory perception, particularly olfaction. The olfactory ability of individuals with ASD has been examined in several psychophysical studies, but the results have been highly variable, which might be primarily due to methodological difficulties in the control of odor stimuli (e.g., the problem of lingering scents). In addition, the neural correlates of olfactory specificities in individuals with ASD remain largely unknown. To date, only one study has investigated this issue using functional magnetic resonance imaging (fMRI). The present study utilized a sophisticated method-a pulse ejection system-to present well-controlled odor stimuli to participants with ASD using an ASD-friendly application. With this advantageous system, we examined their odor detection, identification, and evaluation abilities and measured their brain activity evoked by odors using functional near-infrared spectroscopy (fNIRS). As the odor detection threshold (DT) of participants with ASD was highly variable, these participants were divided into two groups according to their DT: an ASD-Low DT group and an ASD-High DT group. Behavioral results showed that the ASD-High DT group had a significantly higher DT than the typically developing (control) group and the ASD-Low DT group, indicating their insensitivity to the tested odors. In addition, while there was no significant difference in the odor identification ability between groups, there was some discrepancy between the groups' evaluations of odor pleasantness. The brain data identified, for the first time, that neural activity in the right dorsolateral prefrontal cortex (DLPFC) was significantly weaker in the ASD-High DT group than in the control group. Moreover, the strength of activity in the right DLPFC was negatively correlated with the DT. These findings suggest that participants with ASD have impairments in the higher-order function of olfactory processing, such as olfactory working memory and/or attention.

Brief Report: Odour Awareness in Young Children with Autism Spectrum Disorders

The elucidation of odour awareness in children with autism spectrum disorders (ASD) is important. We compared the odour awareness of young children with ASD with those of typical development (TD) children using the Children's Olfactory Behavior in Everyday Life (COBEL) questionnaire, which is a self-report measure that mainly assesses odour awareness. Forty-five young boys (aged 5-6 years), including 20 children with ASD and 25 TD children, participated in this study. The total COBEL score of the young children with ASD was lower than that of the TD children (p < 0.01). Moreover, the total COBEL score was significantly correlated with the total VABS II score (p < 0.05). Our results improve understanding of the odour awareness in children with ASD.

Characterizing Olfactory Function in Children with Autism Spectrum Disorder and Children with Sensory Processing Dysfunction

Abnormalities in olfactory function have been identified in a number of neurological and psychiatric disorders, including Parkinson's disease and schizophrenia. However, little is known about olfactory function in autism spectrum disorder (ASD). The present study aims to assess the olfactory profiles of children with ASD, compared to an age- and sex-matched comparison group of typically developing children and a second clinical control group consisting of non-ASD children with sensory processing dysfunction (SPD). Participants completed a battery of sensory and behavioral assessments including olfactory tasks (Sniffin' Sticks Threshold Test and self-reported valence ratings for two target odorants (phenylethyl alcohol and vanillin) and the University of Pennsylvania Smell Identification Test), and an autism evaluation (Autism Diagnostic Observation Schedule-2). Children with ASD showed intact odor detection with reduced odor identification ability. Poor odor identification was significantly correlated with autism symptom severity. Children with SPD demonstrated reduced odor detection and identification ability. These findings provide evidence for differential patterns of smell processing among ASD and non-ASD neurodevelopmental disorders. Future studies are needed to determine whether the association of impaired olfaction and increased autism symptoms is due to shared etiology.

Superior Identification of Component Odors in a Mixture Is Linked to Autistic Traits in Children and Adults

Most familiar odors are complex mixtures of volatile molecules, which the olfactory system automatically synthesizes into a perceptual whole. However, odors are rarely encountered in isolation; thus, the brain must also separate distinct odor objects from complex and variable backgrounds. In vision, autistic traits are associated with superior performance in tasks that require focus on the local features of a perceptual scene. The aim of the present study was to determine whether the same advantage was observed in the analysis of olfactory scenes. To do this, we compared the ability of 1) 40 young adults (aged 16-35) with high (n = 20) and low levels of autistic traits and 2) 20 children (aged 7-11), with (n = 10) and without an autism spectrum disorder diagnosis, to identify individual odor objects presented within odor mixtures. First, we used a 4-alternative forced choice task to confirm that both adults and children were able to reliably identify 8 blended fragrances, representing food-related odors, when presented individually. We then used the same forced choice format to test participants' ability to identify the odors when they were combined in either binary or ternary mixtures. Adults with high levels of autistic traits showed superior performance on binary but not ternary mixture trials, whereas children with an autism spectrum disorder diagnosis outperformed age-matched neurotypical peers, irrespective of mixture complexity. These findings indicate that the local processing advantages associated with high levels of autistic traits in visual tasks are also apparent in a task requiring analytical processing of odor mixtures.

Individuals With Autism Spectrum Disorder Show Altered Event-Related Potentials in the Late Stages of Olfactory Processing

Atypical sensory reactivities are pervasive among people with autism spectrum disorder (ASD). With respect to olfaction, most previous studies have used psychophysical or questionnaire-based methodologies; thus, the neural basis of olfactory processing in ASD remains unclear. This study aimed to determine the stages of olfactory processing that are altered in ASD. Fourteen young adults with high-functioning ASD (mean age, 21 years; 3 females) were compared with 19 age-matched typically developing (TD) controls (mean age, 21 years; 4 females). Olfactory event-related potentials (OERPs) for 2-phenylethyl alcohol-a rose-like odor-were measured with 64 scalp electrodes while participants performed a simple odor detection task. Significant group differences in OERPs were found in 3 time windows 542 ms after the stimulus onset. The cortical source activities in these time windows, estimated using standardized low-resolution brain electromagnetic tomography, were significantly higher in ASD than in TD in and around the posterior cingulate cortex, which is known to play a crucial role in modality-general cognitive processing. Supplemental Bayesian analysis provided substantial evidence for an alteration in the later stages of olfactory processing, whereas conclusive evidence was not provided for the earlier stages. These results suggest that olfactory processing in ASD is altered at least at the later, modality-general processing stage.

Brief Report: Olfactory Adaptation in Children with Autism Spectrum Disorders

Olfactory adaptation is an important process that allows the individual to adjust to changes in the environment. This process has been proposed to be aberrant in individuals with autism spectrum disorders (ASD). However, few studies have examined olfactory adaptation in children with ASD. We examined olfactory adaptation in children with ASD and typically developing (TD) children using a pulse ejection system, which resolved problems associated with previous laboratory-based olfactory psychophysical studies. Nine children with ASD and nine TD children participated in this study and all participants completed the entire experiment. Using this system, we found that the TD group showed greater adaptation than the ASD group. Our results provide a better understanding of olfactory adaptation in children with ASD.

Relationship Between Odor Identification and Visual Distractors in Children with Autism Spectrum Disorders

Understanding the nature of olfactory abnormalities is crucial for optimal interventions in children with autism spectrum disorders (ASD). However, previous studies that have investigated odor identification in children with ASD have produced inconsistent results. The ability to correctly identify an odor relies heavily on visual inputs in the general population. We tested odor identification in eight children with ASD and eight age-matched children with typical development (TD). After confirming that all children were able to identify each odor without visual input, we measured odor identification under the visual-distractor condition. Odor identification was hindered by visual distractors for all children with ASD but was not affected in all children with TD. Our results improve understanding of odor identification in ASD.

Autistic traits impact on olfactory processing in adolescent girls with Anorexia Nervosa restricting type

The correct functioning of the chemosensory pathway is pivotal for the attitude towards feeding. In some neuropsychiatric disorders, abnormalities of the sensory processing dramatically affect feeding behavior; however, evidences for an olfactory involvement in Anorexia Nervosa (AN) are still controversial. We administered a complete olfactory testing battery, the Sniffin' Sticks Extended Test, to a cohort of 19 girls with Restrictive Anorexia Nervosa (AN-R) and 19 healthy controls. A battery of questionnaires aiming to evaluate eating attitude, psychopathologic disorders and autistic traits was also administered. No difference was found between the two groups in any of the olfactory tasks. Despite the lack of correlation between olfaction and disease severity, however, olfactory performances were related to autistic traits in anorectic girls (r = -0.489, p = 0.039). Girls with AN-R do not appear to have an impaired olfactory function with respect to controls. However, a possible correlation between olfactory ability and autistic traits was discovered. In light of such findings, the role of possible relations between social functioning-related features and olfactory processing in AN-R is discussed.

Effects of familiarization on odor hedonic responses and food choices in children with autism spectrum disorders

This study assessed whether olfactory familiarization can render food odors more pleasant, and consequently food more attractive, to children with autism spectrum disorder. Participants were first presented with a series of food odors (session 1). Then, they were familiarized on four occasions (time window: 5 weeks) with one of the two most neutral odors (the other neutral odor was used as control) (session 2). In session 3, participants smelled the entire series of odors again. Both verbal and facial responses were compared from session 1 to session 3. After session 3, the children were presented with two identical foods (one containing the familiarized odor and one the control odor) and were asked to choose between these foods. Results revealed (1) a specific increase in positive emotions for the familiarized odor and (2) that 68% of the children chose the food associated with the "familiarized odor" (children who chose the "familiarized odor" food exhibited significantly more sensory particularities). These findings suggest that it is possible to modulate olfactory emotions and expand the dietary repertoire of children with autism spectrum disorder. Application of this paradigm may enable innovative prospects for food education in autism.

Oxytocin receptor signaling contributes to olfactory avoidance behavior induced by an unpleasant odorant

Oxytocin (OXT) and its receptor (OXTR) regulate reproductive physiology (i.e. parturition and lactation), sociosexual behavior, learned patterns of behavior and olfactory behavior in social contexts. To characterize the function of OXTR in basic olfactory behavior, the present study compared the behavioral responses of homozygous, heterozygous and wild-type mice when these mice were confronted with an unpleasant odorant (butyric acid) in a custom-made Y-maze in the absence of a social context. Wild-type mice avoided the first encounter with the butyric acid odorant, whereas homozygous and heterozygous mice did not. However, both heterozygous and wild-type mice habituated when confronted with the butyric odorant again on the following 2 days. By contrast, homozygous mice failed to habituate and instead avoided the location of the odorant for at least 3 days. These data suggest that homozygous and heterozygous mice display abnormal olfactory responses to the presentation of an unpleasant odorant. Our studies demonstrate that OXTR plays a critical role in regulating olfactory behavior in the absence of a social context.

Summary: Homozygous mice exhibited abnormal olfactory behaviors, namely failure in the acute avoidance of butyric acid and in habituation behavior, in the absence of a social context.

Olfactory Processing in Male Children with Autism: Atypical Odor Threshold and Identification

Sensory issues are of great interest in ASD diagnosis. However, their investigation is mainly based on external observation (parent reports), with methodological limitations. Unobtrusive olfactory assessment allows studying autism neurosensoriality. Here, 20 male children with high-functioning ASD and 20 matched controls were administered a complete olfactory test battery, assessing olfactory threshold, identification and discrimination. ASD children show lower sensitivity (p = 0.041), lower identification (p = 0.014), and intact odor discrimination (p = 0.199) than controls. Comparing olfactory and clinical scores, a significant correlation was found in ASD between olfactory threshold and the CBCL social problems (p = 0.011) and aggressive behavior (p = 0.012) sub-scales. The pattern featuring peripheral hyposensitivity, high-order difficulties in odor identification and regular subcortical odor discrimination is discussed in light of hypo-priors hypothesis for autism.

Approaches for Assessing Olfaction in Children with Autism Spectrum Disorder

Olfactory traits in individuals with autism spectrum disorder (ASD) are considered the strongest predictors of social impairment. Compared to other sensory abnormalities, olfactory abnormalities in individuals with ASD are poorly understood. In this chapter, we provide an overview of the current assessment in individuals with ASD. Several confounding factors have to be considered when conducting research on olfaction in individuals with ASD. Qualitative measures of olfaction contain only limited information about the olfactory stimuli. In addition, little systematic information is available about individual's actual uses of olfaction in daily life. Only a limited number of experimental studies have performed quantitative measurements of olfactory abnormalities in ASD. Therefore, clarifying the relationship between olfactory traits and the influence of real-life situations in a laboratory setting is very difficult. Some new methodologies for measuring olfactory traits are gradually becoming available. New methods that reveal important links between ASD and olfactory traits should be developed in the future.

Comprehensive Behavioral Analysis of Activating Transcription Factor 5-Deficient Mice

Activating transcription factor 5 (ATF5) is a member of the CREB/ATF family of basic leucine zipper transcription factors. We previously reported that ATF5-deficient (ATF5^-/-) mice demonstrated abnormal olfactory bulb development due to impaired interneuron supply. Furthermore, ATF5^-/- mice were less aggressive than ATF5^+/+ mice. Although ATF5 is widely expressed in the brain, and involved in the regulation of proliferation and development of neurons, the physiological role of ATF5 in the higher brain remains unknown. Our objective was to investigate the physiological role of ATF5 in the higher brain. We performed a comprehensive behavioral analysis using ATF5^-/- mice and wild type littermates. ATF5^-/- mice exhibited abnormal locomotor activity in the open field test. They also exhibited abnormal anxiety-like behavior in the light/dark transition test and open field test. Furthermore, ATF5^-/- mice displayed reduced social interaction in the Crawley’s social interaction test and increased pain sensitivity in the hot plate test compared with wild type. Finally, behavioral flexibility was reduced in the T-maze test in ATF5^-/- mice compared with wild type. In addition, we demonstrated that ATF5^-/- mice display disturbances of monoamine neurotransmitter levels in several brain regions. These results indicate that ATF5 deficiency elicits abnormal behaviors and the disturbance of monoamine neurotransmitter levels in the brain. The behavioral abnormalities of ATF5^-/- mice may be due to the disturbance of monoamine levels. Taken together, these findings suggest that ATF5^-/- mice may be a unique animal model of some psychiatric disorders.

A Meta-Analysis of Odor Thresholds and Odor Identification in Autism Spectrum Disorders

Autism Spectrum Disorders (ASD) are often accompanied by atypical visual, auditory, and tactile sensory behavior. Evidence also suggests alterations of the olfactory system, but the pattern of findings appears mixed. To quantify this pattern systematically, we conducted a meta-analysis. Studies were included if they examined olfactory function (i.e., odor threshold, or odor identification) in ASD compared with healthy age-matched control groups. We also coded for the potential moderators gender, age, and IQ. Articles were identified through computerized literature search using Web of Science, PubMed, and Scopus databases. A total of 11 articles compared odor threshold and/or odor identification between cases and controls (for threshold, n = 143 ASD and 148 controls; and for identification, n = 132 ASD and 139 controls). Effects sizes showed a substantial heterogeneity. As a result, the 95% prediction intervals were wide and ranged between a large negative and a large positive effect size for odor threshold, [-1.86, 2.05], and for odor identification, [-1.51, 2.52]. Exploratory analyses suggested that age and IQ may be potential moderators. To conclude, the large heterogeneity is consistent with the notion of both hyposensitivity and hypersensitivity in individuals with ASD. However, future research needs to predict and test the specific direction of the effect to provide convincing evidence for atypical olfactory functions in ASD.