Perceptual and neural response to affective tactile texture stimulation in adults with autism spectrum disorders

Exploring social touch in autistic and non-autistic adults via a self-report body-painting task: The role of sex, social context and body area

LAY ABSTRACT

What is already known about the topic?At least in neurotypical individuals, social touch represents an important channel for emotional communication associated with social bonding and pain/anxiety modulation. Autistic adults report to avoid social touch more and to have different tactile sensitivity than their non-autistic comparisons.What this paper adds?Few studies specifically investigated social touch in autistic individuals, and none of them examined the role of participants' sex, social context in which social touch occurs, and specific body areas being touched. In our study, adult participants reported how pleasant, erogenous and appropriate they would consider touches delivered by another person over their entire body in intimate (date), friendly (dance class) and professional (physiotherapy-massage session) social contexts. Autistic adults reported social touch to be less pleasant, erogenous and appropriate specifically in intimate and friendly social contexts and in body areas typically touched in these situations. Importantly, autistic females seem more at risk to experience unpleasant social touch as, although they considered it more unpleasant than non-autistic females and autistic males, they did consider it similarly appropriate in professional social contexts where touch is normed to be socially appropriate.Implications for practice, research or policyOur results might improve awareness and understanding about autistic adults' different, and often more discomforting, experience of social touch and thus help consider and respect it during everyday social interactions. Our results might also benefit future research investigating, for instance, the neural underpinnings of social touch differences in autism or aiming at developing support for autistic individuals seeking help in the diverse spheres of social touch.

Maternal prenatal depressive symptoms and child brain responses to affective touch at two years of age

BACKGROUND

Touch is an essential form of mother-child interaction, instigating better social bonding and emotional stability.

METHODS

We used diffuse optical tomography to explore the relationship between total haemoglobin (HbT) responses to affective touch in the child's brain at two years of age and maternal self-reported prenatal depressive symptoms (EPDS). Affective touch was implemented via slow brushing of the child's right forearm at 3 cm/s and non-affective touch via fast brushing at 30 cm/s and HbT responses were recorded on the left hemisphere.

RESULTS

We discovered a cluster in the postcentral gyrus exhibiting a negative correlation (Pearson's r = -0.84, p = 0.015 corrected for multiple comparisons) between child HbT response to affective touch and EPDS at gestational week 34. Based on region of interest (ROI) analysis, we found negative correlations between child responses to affective touch and maternal prenatal EPDS at gestational week 14 in the precentral gyrus, Rolandic operculum and secondary somatosensory cortex. The responses to non-affective touch did not correlate with EPDS in these regions.

LIMITATIONS

The number of mother-child dyads was 16. However, by utilising high-density optode arrangements, individualised anatomical models, and video and accelerometry to monitor movement, we were able to minimize methodological sources of variability in the data.

CONCLUSIONS

The results show that maternal depressive symptoms during pregnancy may be associated with reduced child responses to affective touch in the temporoparietal cortex. Responses to affective touch may be considered as potential biomarkers for psychosocial development in children. Early identification of and intervention in maternal depression may be important already during early pregnancy.

Autonomic and hedonic response to affective touch in autism spectrum disorder

Interpersonal touch plays a crucial role in shaping relationships and encouraging social connections. Failure in processing tactile input or abnormal tactile sensitivity may hamper social behaviors and have severe consequences in individuals' relational lives. Autism Spectrum Disorder (ASD) is characterized by both sensory disruptions and social impairments, making affective touch an ideal meeting point for understanding these features in ASD individuals. By integrating behavioral and physiological measures, we investigated the effects of affective touch on adult individuals with ASD from both an implicit and explicit perspective. Specifically, at an implicit level, we investigated whether and how receiving an affective touch influenced participants' skin conductance tonic and phasic components. At the explicit level, we delved into the affective and unpleasant features of affective touch. Overall, we observed lower skin conductance level in ASD compared to TD subjects. Interestingly, the typically developing (TD) group showed an increased autonomic response for affective touch compared to a control touch, while ASD subjects' autonomic response did not differ between the two conditions. Furthermore, ASD participants provided higher ratings for both the affective and unpleasant components of the touch, compared to TD subjects. Our results reveal a noteworthy discrepancy in ASD population between the subjective experience, characterized by amplified hedonic but also unpleasant responses, and the physiological response, marked by a lack of autonomic activation related to affective touch. This insightful dissociation seems crucial for a deeper understanding of the distinctive challenges characterizing people with ASD and may have implications for diagnosis and therapeutic approaches.

People with Autism Spectrum Disorder Could Interact More Easily with a Robot than with a Human: Reasons and Limits

Individuals with Autism Spectrum Disorder show deficits in communication and social interaction, as well as repetitive behaviors and restricted interests. Interacting with robots could bring benefits to this population, notably by fostering communication and social interaction. Studies even suggest that people with Autism Spectrum Disorder could interact more easily with a robot partner rather than a human partner. We will be looking at the benefits of robots and the reasons put forward to explain these results. The interest regarding robots would mainly be due to three of their characteristics: they can act as motivational tools, and they are simplified agents whose behavior is more predictable than that of a human. Nevertheless, there are still many challenges to be met in specifying the optimum conditions for using robots with individuals with Autism Spectrum Disorder.

A sensory signature of unaffected biological parents predicts the risk of autism in their offspring

AIM

Despite the emphasis on sensory dysfunction phenotypes in the revised diagnostic criteria for autism spectrum disorder (ASD), there has been limited research, particularly in the field of neurobiology, investigating the concordance in sensory features between individuals with ASD and their genetic relatives. Therefore, our objective was to examine whether neurobehavioral sensory patterns could serve as endophenotypic markers for ASD.

METHODS

We combined questionnaire- and lab-based sensory evaluations with sensory fMRI measures to examine the patterns of sensory responsivity in 30 clinically diagnosed with ASD, 26 matched controls (CON), and 48 biological parents for both groups (27 parents of individuals with ASD [P-ASD] and 21 for individuals with CON [P-CON]).

RESULTS

The ASD and P-ASD groups had higher sensory responsivity and rated sensory stimuli as more unpleasant than the CON and P-CON groups, respectively. They also exhibited greater hemodynamic responses within the sensory cortices. Overlapping activations were observed within these sensory cortices in the ASD and P-ASD groups. Using a machine learning approach with robust prediction models across cohorts, we demonstrated that the sensory profile of biological parents accurately predicted the likelihood of their offspring having ASD, achieving a prediction accuracy of 71.4%.

CONCLUSIONS

These findings provide support for the hereditary basis of sensory alterations in ASD and suggest a potential avenue to improve ASD diagnosis by utilizing the sensory signature of biological parents, especially in families with a high risk of ASD. This approach holds promising prospects for early detection, even before the birth of the offspring.

Differences in temporal profile of brain responses by pleasantness of somatosensory stimulation in autistic individuals

Purpose/Aim. Autistic individuals may show either hyper- or hypo- responsiveness to touch compared to non-autistic individuals. These behavioural responses depend on perceptual and evaluative mechanisms, which unfold sequentially and thus can be distinguished by exploring the timing of neural responses. In this study, we examined neural response timing to pleasant, unpleasant, and affectively neutral textures, to determine whether these perceptual versus evaluative subprocesses differ in autism and how each subprocess contributes to behavioural responses.Materials and Methods. Our sample included n = 13 autistic and n = 14 non-autistic adults who completed functional magnetic resonance imaging. We analysed early, intermediate, and late phases of the tactile response, derived from studies of noxious tactile stimulation, to three different textures.Results. The autistic group showed distinct differences from the non-autistic group to each of the textures, showing earlier, somatosensory differences in response to the pleasantly and unpleasantly rated textures and later, frontomotor differences in response to the neutrally rated texture. Further, reduced early phase response to the pleasant texture correlated with increased sensory seeking behaviour.Conclusions. While preliminary, these results suggest distinct patterns between autistic and non-autistic individuals in how the neural response to touch unfolds and its correspondence with the perceived pleasantness of tactile experience. The findings suggest perceptual differences in response to affectively charged textures and evaluative differences in response to neutral, ambiguous textures. These temporal properties may inform future studies of tactile processing in autism, lending a better understanding of how individuals differ in their sensory experiences across contexts.

Autistic Traits Related to the Importance of Interpersonal Touch and Appreciation of Observed Touch during COVID-19 Social Distancing

Studies have confirmed the significance of touch for psychological wellbeing. Social distancing regulations during the COVID-19 pandemic reduced people's ability to engage in interpersonal touch and caused increased an appreciation for observed touch, as well as a longing for touch within the neurotypical population. Yet, while the impact of social distancing and the importance of touch are evident in neurotypical individuals, it remains unclear how these factors manifest in autistic individuals. Previous research has related high levels of autistic traits to reduced levels of perceived pleasantness of touch and a reduced interest in interpersonal touch. Our study aimed to examine the differences in the appreciation of observed touch and longing for touch during social distancing between individuals with low and high levels of autistic traits. We conducted an online survey on autistic traits, the appreciation of observed CT-optimal touch and longing for touch. Consistent with our predictions, our results confirmed that individuals with high levels of autistic traits evaluated videos depicting CT-optimal touch less favorably compared to those with lower scores on autistic traits. Additionally, only the group with low levels of autistic traits exhibited a longing for touch during social distancing, whereas the group with high levels of autistic traits did not. The results provide insights in the appreciation of touch in relation to autistic traits during the unique circumstances of the COVID-19 pandemic.

No differences in implicit hand maps among different degrees of autistic traits

People with autism spectrum disorder (ASD) or higher levels of autistic traits have atypical characteristics in sensory processing. Atypicalities have been reported for proprioceptive judgments, which are tightly related to internal bodily representations underlying position sense. However, no research has directly investigated whether self-bodily representations are different in individuals with ASD. Implicit hand maps, estimated based on participants' proprioceptive sensations without sight of their hand, are known to be distorted such that the shape is stretched along the medio-lateral hand axis even for neurotypical participants. Here, with the view of ASD as falling on a continuous distribution among the general population, we explored differences in implicit body representations along with autistic traits by focusing on relationships between autistic traits and the magnitudes of the distortions in implicit hand maps (N ~ 100). We estimated the magnitudes of distortions in implicit hand maps both for fingers and hand surfaces on the dorsal and palmar sides of the hand. Autistic traits were measured by questionnaires (Autism Spectrum [AQ] and Empathy/Systemizing [EQ-SQ] Quotients). The distortions in implicit hand maps were replicated in our experimental situations. However, there were no significant relationships between autistic traits and the magnitudes of the distortions as well as within-individual variabilities in the maps and localization performances. Consistent results were observed from comparisons between IQ-matched samples of people with and without a diagnosis of ASD. Our findings suggest that there exist perceptual and neural processes for implicit body representations underlying position sense consistent across levels of autistic traits.

Caught on the surface: Tustin on autistic experience

According to Frances Tustin, the core of autism is found in sensory modifications-and tactile modifications in particular. Tustin argues that sensory experiences may become self-absorbed to such an extent that the sensory environment experientially flattens into a two-dimensional "feel," which complicates the individual's relations with the external environment and other people. Focusing on these fundamental modifications and their experiential consequences, the article introduces Tustin's main insight in terms of collapse of intentional depth, suggesting that this collapse concerns not only concrete spatial depth, but symbolic and intersubjective depth as well. By so doing, the article illustrates how Tustin's ideas render intelligible certain commonly recognized features of autism, such as "deficits in the ability to initiate and to sustain reciprocal social interaction and social communication" and "restricted, repetitive, and inflexible patterns of behavior, interests or activities" (ICD-11).

Maternal autistic traits and antenatal pain by cross-sectional analysis of the Japan Environment and Children's Study

The aim of cross-sectional study was to investigate whether the presence of autistic traits in pregnant women was positively associated with the prevalence and severity of antenatal pain. We analyzed 89,068 pregnant women from a Japanese national birth cohort cross-sectionally. Autistic traits were assessed using the Japanese version of the Autism-Spectrum Quotient short form (AQ-10-J). Antenatal pain was measured using the SF-8 bodily pain item (SF-8-Pain). Antenatal pain in the second to third trimester during pregnancy was categorized into three groups: without pain, mild pain, and moderate-to-severe pain. Participants were divided into eight groups by AQ-10-J score: seven consecutive scoring groups (scores 0-6), and those above the cut-off (≥ 7) for probable autistic spectrum disorders. Odds ratios (OR) for the prevalence of mild and moderate-to-severe pain were calculated for each AQ-10-J scoring group (reference: without pain group) using multinominal logistic regression analysis. Autistic traits were positively associated with mild and moderate-to-severe pain in a dose-response manner, but the association with moderate-to-severe pain was strongest. Fully-adjusted ORs (95% confidence intervals) for moderate-to-severe pain were: 1.01 (0.91-1.13) for 1 point, 1.13 (1.02-1.25) for 2 points, 1.16 (1.04-1.29) for 3 points, 1.20 (1.07-1.34) for 4 points, 1.23 (1.09-1.40) for 5 points, 1.27 (1.10-1.47) for 6 points, and 1.24 (1.05-1.46) for ≥ 7 points (AQ-10-J cut-off). We identified an association between maternal autistic traits and antenatal pain. Maternal autistic traits may need to be considered when addressing antenatal pain during healthcare for expectant mothers.

A working taxonomy for describing the sensory differences of autism

BACKGROUND

Individuals on the autism spectrum have been long described to process sensory information differently than neurotypical individuals. While much effort has been leveraged towards characterizing and investigating the neurobiology underlying the sensory differences of autism, there has been a notable lack of consistency in the terms being used to describe the nature of those differences.

MAIN BODY

We argue that inconsistent and interchangeable terminology-use when describing the sensory differences of autism has become problematic beyond mere pedantry and inconvenience. We begin by highlighting popular terms that are currently being used to describe the sensory differences of autism (e.g. "sensitivity", "reactivity" and "responsivity") and discuss why poor nomenclature may hamper efforts towards understanding the aetiology of sensory differences in autism. We then provide a solution to poor terminology-use by proposing a hierarchical taxonomy for describing and referring to various sensory features.

CONCLUSION

Inconsistent terminology-use when describing the sensory features of autism has stifled discussion and scientific understanding of the sensory differences of autism. The hierarchical taxonomy proposed was developed to help resolve lack of clarity when discussing the sensory differences of autism and to place future research targets at appropriate levels of analysis.

Clothes, Sensory Experiences and Autism: Is Wearing the Right Fabric Important?

Tactile defensiveness in autistic individuals is the least investigated sensory modality. The current multi-component, explorative study aimed to understand the experiences of ten autistic adults regarding tactile defensiveness and fabrics, using semi-structured, one-to-one interviews. Participants were asked to discuss the effects of seven provided samples of fabrics and were also asked to bring their 'favourite' fabric (s) and express their thoughts about their choices. Using Interpretative Phenomenological Analysis and Content Analysis, the findings showed that some fabrics can impact individuals' reported wellbeing. Participants' experiences with several stimuli appeared to have helped them implement coping strategies. By understanding tactile defensiveness, society could move towards increasing autism-friendly approaches with appropriate fabrics. Recommendations for future research, policy and practice are also discussed.

Topology of the lateral visual system: The fundus of the superior temporal sulcus and parietal area H connect nonvisual cerebrum to the lateral occipital lobe

BACKGROUND AND PURPOSE

Mapping the topology of the visual system is critical for understanding how complex cognitive processes like reading can occur. We aim to describe the connectivity of the visual system to understand how the cerebrum accesses visual information in the lateral occipital lobe.

METHODS

Using meta-analytic software focused on task-based functional MRI studies, an activation likelihood estimation (ALE) of the visual network was created. Regions of interest corresponding to the cortical parcellation scheme previously published under the Human Connectome Project were co-registered onto the ALE to identify the hub-like regions of the visual network. Diffusion Spectrum Imaging-based fiber tractography was performed to determine the structural connectivity of these regions with extraoccipital cortices.

RESULTS

The fundus of the superior temporal sulcus (FST) and parietal area H (PH) were identified as hub-like regions for the visual network. FST and PH demonstrated several areas of coactivation beyond the occipital lobe and visual network. Furthermore, these parcellations were highly interconnected with other cortical regions throughout extraoccipital cortices related to their nonvisual functional roles. A cortical model demonstrating connections to these hub-like areas was created.

CONCLUSIONS

FST and PH are two hub-like areas that demonstrate extensive functional coactivation and structural connections to nonvisual cerebrum. Their structural interconnectedness with language cortices along with the abnormal activation of areas commonly located in the temporo-occipital region in dyslexic individuals suggests possible important roles of FST and PH in the integration of information related to language and reading. Future studies should refine our model by examining the functional roles of these hub areas and their clinical significance.

Comparing sensory processing in children with Down syndrome to a mental age matched sample of children with autism, other developmental disabilities, and typically developing children

BACKGROUND

Atypical sensory processing impacts children with intellectual and developmental disabilities (IDD). Research has focused on SP in individuals with autism spectrum disorder (ASD); comparatively, little has been written regarding individuals with Down syndrome (DS) and IDDs.

AIMS

We compared patterns of sensory processing in children with DS to children with ASD, other IDDs, and typically developing (TD) peers examining the relationship among different sensory processing measures.

METHODS AND PROCEDURES

We analyzed cross-sectional data using two caregiver questionnaires (SP, SEQ) and one observational measure (SPA). Groups were compared on three sensory processing patterns: hyporesponsiveness; hyperresponsiveness; and sensory interests, repetitions, and seeking (SIRS) via ANOVA. We assessed concordance through correlations.

OUTCOMES AND RESULTS

Children with DS, IDD, and ASD demonstrated more atypical sensory processing behaviors than TD peers. Children with ASD exhibited the most atypical responses across all measures, significantly more than DS children on all but one subscale. The IDD and DS groups differed on several measures. Measurement concordance was higher between caregiver-report versus observational assessment.

CONCLUSIONS AND IMPLICATIONS

Differences between three clinical groups indicate that sensory processing features may differ across clinical populations regardless of cognitive functioning. Lower concordance between caregiver-report and observation measures highlights the need to understand sensory processing expression across different tasks and environments.

Brainstem white matter microstructure is associated with hyporesponsiveness and overall sensory features in autistic children

BACKGROUND

Elevated or reduced responses to sensory stimuli, known as sensory features, are common in autistic individuals and often impact quality of life. Little is known about the neurobiological basis of sensory features in autistic children. However, the brainstem may offer critical insights as it has been associated with both basic sensory processing and core features of autism.

METHODS

Diffusion-weighted imaging (DWI) and parent-report of sensory features were acquired from 133 children (61 autistic children with and 72 non-autistic children, 6-11 years-old). Leveraging novel DWI processing techniques, we investigated the relationship between sensory features and white matter microstructure properties (free-water-elimination-corrected fractional anisotropy [FA] and mean diffusivity [MD]) in precisely delineated brainstem white matter tracts. Follow-up analyses assessed relationships between microstructure and sensory response patterns/modalities and analyzed whole brain white matter using voxel-based analysis.

RESULTS

Results revealed distinct relationships between brainstem microstructure and sensory features in autistic children compared to non-autistic children. In autistic children, more prominent sensory features were generally associated with lower MD. Further, in autistic children, sensory hyporesponsiveness and tactile responsivity were strongly associated with white matter microstructure in nearly all brainstem tracts. Follow-up voxel-based analyses confirmed that these relationships were more prominent in the brainstem/cerebellum, with additional sensory-brain findings in the autistic group in the white matter of the primary motor and somatosensory cortices, the occipital lobe, the inferior parietal lobe, and the thalamic projections.

LIMITATIONS

All participants communicated via spoken language and acclimated to the sensory environment of an MRI session, which should be considered when assessing the generalizability of this work to the whole of the autism spectrum.

CONCLUSIONS

These findings suggest unique brainstem white matter contributions to sensory features in autistic children compared to non-autistic children. The brainstem correlates of sensory features underscore the potential reflex-like nature of behavioral responses to sensory stimuli in autism and have implications for how we conceptualize and address sensory features in autistic populations.

Atypical Response to Affective Touch in Children with Autism: Multi-Parametric Exploration of the Autonomic System

This study aimed at evaluating the autonomic response to pleasant affective touch in children with Autism Spectrum Disorders (ASD) and age-matched typically developing (TD) peers, thanks to multiple autonomic nervous system (ANS) parameters and by contrasting CT (C-tactile fibers) high- vs. low-density territory stimulations. We measured pupil diameter, skin conductance, and heart rate during gentle stroking of two skin territories (CT high- and low-density, respectively, forearm and palm of the hand) in thirty 6-12-year-old TD children and twenty ASD children. TD children showed an increase in pupil diameter and skin conductance associated with a heart rate deceleration in response to tactile stimulations at the two locations. Only the pupil was influenced by the stimulated location, with a later dilation peak following CT low-density territory stimulation. Globally, ASD children exhibited reduced autonomic responses, as well as different ANS baseline values compared to TD children. These atypical ANS responses to pleasant touch in ASD children were not specific to CT-fiber stimulation. Overall, these results point towards both basal autonomic dysregulation and lower tactile autonomic evoked responses in ASD, possibly reflecting lower arousal and related to social disengagement.

Endowing a NAO Robot With Practical Social-Touch Perception

Social touch is essential to everyday interactions, but current socially assistive robots have limited touch-perception capabilities. Rather than build entirely new robotic systems, we propose to augment existing rigid-bodied robots with an external touch-perception system. This practical approach can enable researchers and caregivers to continue to use robotic technology they have already purchased and learned about, but with a myriad of new social-touch interactions possible. This paper presents a low-cost, easy-to-build, soft tactile-perception system that we created for the NAO robot, as well as participants’ feedback on touching this system. We installed four of our fabric-and-foam-based resistive sensors on the curved surfaces of a NAO’s left arm, including its hand, lower arm, upper arm, and shoulder. Fifteen adults then performed five types of affective touch-communication gestures (hitting, poking, squeezing, stroking, and tickling) at two force intensities (gentle and energetic) on the four sensor locations; we share this dataset of four time-varying resistances, our sensor patterns, and a characterization of the sensors’ physical performance. After training, a gesture-classification algorithm based on a random forest identified the correct combined touch gesture and force intensity on windows of held-out test data with an average accuracy of 74.1%, which is more than eight times better than chance. Participants rated the sensor-equipped arm as pleasant to touch and liked the robot’s presence significantly more after touch interactions. Our promising results show that this type of tactile-perception system can detect necessary social-touch communication cues from users, can be tailored to a variety of robot body parts, and can provide HRI researchers with the tools needed to implement social touch in their own systems.

Atypically high influence of subcortical activity on primary sensory regions in autism

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The age-dependent decrease of subcortico-cortical connectivity is attenuated in ASD.

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Primary sensory regions remain less segregated from subcortical activity in ASD.

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This could underlie an excessive amount of sensory input relayed to the cortex.

Background

Hypersensitivity, stereotyped behaviors and attentional problems in autism spectrum disorder (ASD) are compatible with inefficient filtering of undesired or irrelevant sensory information at early stages of neural processing. This could stem from the persistent overconnectivity between primary sensory regions and deep brain nuclei in both children and adults with ASD – as reported by several previous studies – which could reflect a decreased or arrested maturation of brain connectivity. However, it has not yet been investigated whether this overconnectivity can be modelled as an excessive directional influence of subcortical brain activity on primary sensory cortical regions in ASD, with respect to age-matched typically developing (TD) individuals.

Methods

To this aim, we used dynamic causal modelling to estimate (1) the directional influence of subcortical activity on cortical processing and (2) the functional segregation of primary sensory cortical regions from subcortical activity in 166 participants with ASD and 193 TD participants from the Autism Brain Imaging Data Exchange (ABIDE). We then specifically tested the hypothesis that the age-related changes of these indicators of brain connectivity would differ between the two groups.

Results

We found that in TD participants age was significantly associated with decreased influence of subcortical activity on cortical processing, paralleled by an increased functional segregation of cortical sensory processing from subcortical activity. Instead these effects were highly reduced and mostly absent in ASD participants, suggesting a delayed or arrested development of the segregation between subcortical and cortical sensory processing in ASD.

Conclusion

This atypical configuration of subcortico-cortical connectivity in ASD can result in an excessive amount of unprocessed sensory input relayed to the cortex, which is likely to impact cognitive functioning in everyday situations where it is beneficial to limit the influence of basic sensory information on cognitive processing, such as activities requiring focused attention or social interactions.

Looking Back at the Next 40 Years of ASD Neuroscience Research

During the last 40 years, neuroscience has become one of the most central and most productive approaches to investigating autism. In this commentary, we assemble a group of established investigators and trainees to review key advances and anticipated developments in neuroscience research across five modalities most commonly employed in autism research: magnetic resonance imaging, functional near infrared spectroscopy, positron emission tomography, electroencephalography, and transcranial magnetic stimulation. Broadly, neuroscience research has provided important insights into brain systems involved in autism but not yet mechanistic understanding. Methodological advancements are expected to proffer deeper understanding of neural circuitry associated with function and dysfunction during the next 40 years.

People With High Autistic Traits Show Fewer Consensual Crossmodal Correspondences Between Visual Features and Tastes

Crossmodal correspondences between visual features (e.g., color/shape) and tastes have been extensively documented in recent years. Visual colors and shapes have been shown to consensually match to specific tastes. Meanwhile, individuals with autism spectrum disorder are reported to have atypical sensory processing and deficits in multisensory integration. However, the influence of autistic traits on the formation of such correspondences is relatively unknown. Here, we examined whether autistic traits could influence visual–taste associations using an online questionnaire survey among Japanese participants. The results showed that the participants exhibited strong color–taste, shape–taste, and shape–color associations, and the proportions of choosing the consensual color–taste/shape–color associations were significantly associated with autistic traits. The participants with higher autistic quotient scores chose fewer of the consensual color–taste/shape–color associations while there was no difference in choosing shape–taste associations. We interpreted the results as statistical learning with a reduced prior knowledge effect in participants with higher autistic quotient scores.

Investigating sensory response to physical discomfort in children with autism spectrum disorder using near-infrared spectroscopy

Self-reporting of pain can be difficult in populations with communication challenges or atypical sensory processing, such as children with autism spectrum disorder (ASD). Consequently, pain can go untreated. An objective method to identify discomfort would be valuable to individuals unable to express or recognize their own bodily distress. Near-infrared spectroscopy (NIRS) is a brain-imaging modality that is suited for this application. We evaluated the potential of detecting a cortical response to discomfort in the ASD population using NIRS. Using a continuous-wave spectrometer, prefrontal and parietal measures were collected from 15 males with ASD and 7 typically developing (TD) males 10-15 years of age. Participants were exposed to a noxious cold stimulus by immersing their hands in cold water and tepid water as a baseline task. Across all participants, the magnitude and timing of the cold and tepid water-induced brain responses were significantly different (p < 0.001). The effect of the task on the brain response depended on the study group (group x task: p < 0.001), with the ASD group exhibiting a blunted response to the cold stimulus. Findings suggest that NIRS may serve as a tool for objective pain assessment and atypical sensory processing.

A huggable device can reduce the stress of calling an unfamiliar person on the phone for individuals with ASD

Individuals with autism spectrum disorders (ASD) are often not comfortable during mobile-phone conversations with unfamiliar people. “Hugvie” is a pillow with a human-like shape that has been designed to provide users with the tactile sensation of hugging another person during phone conversations to promote feelings of comfort and trust in the speaker toward their conversation partners. Our primary aim was to examine whether physical contact by hugging a Hugvie could reduce the stress of speaking with an unfamiliar person on the phone in individuals with ASD. We enrolled 24 individuals and requested them to carry out phone conversations either using only a mobile phone or using a mobile phone along with the Hugvie. All participants in both groups completed questionnaires designed to evaluate their self-confidence while talking on the phone, and also provided salivary cortisol samples four times each day. Our analysis revealed that the medium of communication was a significant factor, indicating that individuals with ASD who spoke with an unfamiliar person on the phone while hugging a Hugvie had stronger self-confidence and lower stress levels than those who did not use Hugvie. Hence, we recommend that huggable devices be used as adjunctive tools to support individuals with ASD during telephonic conversations with unfamiliar people.

Clothes, Sensory Experiences and Autism: Is Wearing the Right Fabric Important?

Tactile defensiveness in autistic individuals is the least investigated sensory modality. The current multi-component, explorative study aimed to understand the experiences of ten autistic adults regarding tactile defensiveness and fabrics, using semi-structured, one-to-one interviews. Participants were asked to discuss the effects of seven provided samples of fabrics and were also asked to bring their 'favourite' fabric (s) and express their thoughts about their choices. Using Interpretative Phenomenological Analysis and Content Analysis, the findings showed that some fabrics can impact individuals' reported wellbeing. Participants' experiences with several stimuli appeared to have helped them implement coping strategies. By understanding tactile defensiveness, society could move towards increasing autism-friendly approaches with appropriate fabrics. Recommendations for future research, policy and practice are also discussed.

Cortical Morphology in Autism: Findings from a Cortical Shape-Adaptive Approach to Local Gyrification Indexing

It has been challenging to elucidate the differences in brain structure that underlie behavioral features of autism. Prior studies have begun to identify patterns of changes in autism across multiple structural indices, including cortical thickness, local gyrification, and sulcal depth. However, common approaches to local gyrification indexing used in prior studies have been limited by low spatial resolution relative to functional brain topography. In this study, we analyze the aforementioned structural indices, utilizing a new method of local gyrification indexing that quantifies this index adaptively in relation to specific sulci/gyri, improving interpretation with respect to functional organization. Our sample included n = 115 autistic and n = 254 neurotypical participants aged 5-54, and we investigated structural patterns by group, age, and autism-related behaviors. Differing structural patterns by group emerged in many regions, with age moderating group differences particularly in frontal and limbic regions. There were also several regions, particularly in sensory areas, in which one or more of the structural indices of interest either positively or negatively covaried with autism-related behaviors. Given the advantages of this approach, future studies may benefit from its application in hypothesis-driven examinations of specific brain regions and/or longitudinal studies to assess brain development in autism.

The functional neural architecture of dysfunctional reward processing in autism

Functional imaging studies have found differential neural activation patterns during reward-paradigms in patients with autism spectrum disorder (ASD) compared to neurotypical controls. However, publications report conflicting results on the directionality and location of these aberrant activations. We here quantitatively summarized relevant fMRI papers in the field using the anatomical likelihood estimation (ALE) algorithm. Patients with ASD consistently showed hypoactivations in the striatum across studies, mainly in the right putamen and accumbens. These regions are functionally involved in the processing of rewards and are enrolled in extensive neural networks involving limbic, cortical, thalamic and mesencephalic regions. The striatal hypo-activations found in our ALE meta-analysis, which pooled over contrasts derived from the included studies on reward-processing in ASD, highlight the role of the striatum as a key neural correlate of impaired reward processing in autism. These changes were present for studies using social and non-social stimuli alike. The involvement of these regions in extensive networks associated with the processing of both positive and negative emotion alike might hint at broader impairments of emotion processing in the disorder.

Strengths and weaknesses of affective touch studies over the lifetime: A systematic review

C-Tactile (CT) fibers are activated by slow, caress-like stimulations, and convey a specific tactile processing of hedonic and interpersonal components, defined as affective touch. Given the beneficial effects deriving from affective tactile experiences in social interactions at all ages, a systematic review of experimental studies on affective touch perception across the lifespan was performed with the aims of 1) examining whether and how affective touch has been studied in a systematic manner throughout the lifespan; 2) verifying whether the pleasantness associated to affective stimulations is found during the entire lifespan. Empirical human studies on affective touch were searched in two databases (PubMed, PsychINFO) and 112 articles were retrieved. Results indicated that most of the studies recruited participants with a mean age ranging from 18 to 40 years, whereas other age ranges came out as under-represented or not represented at all. Despite high heterogeneity across studies, affective touch was considered as a pleasant experience across the lifetime, and it was associated to specific psychophysiological patterns in infants and adults.

Altered relationship between subjective perception and central representation of touch hedonics in adolescents with autism-spectrum disorder

An impairment of social communication is a core symptom of autism-spectrum disorder (ASD). Affective touch is an important means of social interaction, and C-Tactile (CT) afferents are thought to play a key role in the peripheral detection and encoding of these stimuli. Exploring the neural and behavioral mechanisms for processing CT-optimal touch (~3 cm/s) may therefore provide useful insights into the pathophysiology of ASD. We examined the relationship between touch hedonics (i.e. the subjective pleasantness with which affective touch stimuli are perceived) and neural processing in the posterior superior temporal sulcus (pSTS). This region is less activated to affective touch in individuals with ASD, and, in typically developing individuals (TD), is correlated positively with touch pleasantness. TD and ASD participants received brushing stimuli at CT-optimal, and CT-non-optimal speeds during fMRI. Touch pleasantness and intensity ratings were collected, and affective touch awareness, a measure of general touch hedonics was calculated. As expected, slow touch was perceived as more pleasant and less intense than fast touch in both groups, whereas affective touch awareness was moderately higher in TD compared to ASD. There was a strong, positive correlation between right pSTS activation and affective touch awareness in TD, but not in ASD. Our findings suggest that altered neural coupling between right pSTS and touch hedonics in ASD may be associated with social touch avoidance in ASD.

Tactile cortical responses and association with tactile reactivity in young children on the autism spectrum

Background

Unusual behavioral reactions to sensory stimuli are frequently reported in individuals on the autism spectrum (AS). Despite the early emergence of sensory features (< age 3) and their potential impact on development and quality of life, little is known about the neural mechanisms underlying sensory reactivity in early childhood autism.

Methods

Here, we used electroencephalography (EEG) to investigate tactile cortical processing in young children aged 3–6 years with autism and in neurotypical (NT) children. Scalp EEG was recorded from 33 children with autism, including those with low cognitive and/or verbal abilities, and 45 age- and sex-matched NT children during passive tactile fingertip stimulation. We compared properties of early and later somatosensory-evoked potentials (SEPs) and their adaptation with repetitive stimulation between autistic and NT children and assessed whether these neural measures are linked to “real-world” parent-reported tactile reactivity.

Results

As expected, we found elevated tactile reactivity in children on the autism spectrum. Our findings indicated no differences in amplitude or latency of early and mid-latency somatosensory-evoked potentials (P50, N80, P100), nor adaptation between autistic and NT children. However, latency of later processing of tactile information (N140) was shorter in young children with autism compared to NT children, suggesting faster processing speed in young autistic children. Further, correlational analyses and exploratory analyses using tactile reactivity as a grouping variable found that enhanced early neural responses were associated with greater tactile reactivity in autism.

Limitations

The relatively small sample size and the inclusion of a broad range of autistic children (e.g., with low cognitive and/or verbal abilities) may have limited our power to detect subtle group differences and associations. Hence, replications are needed to verify these results.

Conclusions

Our findings suggest that electrophysiological somatosensory cortex processing measures may be indices of “real-world” tactile reactivity in early childhood autism. Together, these findings advance our understanding of the neurophysiological mechanisms underlying tactile reactivity in early childhood autism and, in the clinical context, may have therapeutic implications.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13229-021-00435-9.

Bliss in and Out of the Body: The (Extra)Corporeal Space Is Impervious to Social Pleasant Touch

Slow, gentle stimulation of hairy skin is generally accompanied by hedonic sensations. This phenomenon, also known as (positive) affective touch, is likely to be the basis of affiliative interactions with conspecifics by promoting inter-individual bindings. Previous studies on healthy humans have demonstrated that affective touch can remarkably impact behavior. For instance, by administering the Rubber Hand Illusion (RHI) paradigm, the embodiment of a fake hand enhances after a slow, affective touch compared to a fast, neutral touch. However, results coming from this area are not univocal. In addition, there are no clues in the existing literature on the relationship between affective touch and the space around our body. To overcome these lacks, we carried out two separate experiments where participants underwent a RHI paradigm (Experiment 1) and a Visuo-Tactile Interaction task (Experiment 2), designed to tap into body representation and peripersonal space processing, respectively. In both experiments, an affective touch (CT-optimal, 3 cm/s) and neutral touch (CT-suboptimal, 18 cm/s) were delivered by the experimenter on the dorsal side of participants’ hand through a “skin to skin” contact. In Experiment 1, we did not find any modulation of body representation—not at behavioral nor at a physiological level—by affective touch. In Experiment 2, no visuo-tactile spatial modulation emerged depending upon the pleasantness of the touch received. These null findings are interpreted in the light of the current scientific context where the real nature of affective touch is often misguided, and they offer the possibility to pave the way for understanding the real effects of affective touch on body/space representation.

Somatosensory Temporal Discrimination in Autism Spectrum Disorder

Sensory differences are common in Autism Spectrum Disorder (ASD). While there is no well-accepted method to measure sensory differences objectively, there is accumulating evidence from recent years concerning sensory perception, including data concerning temporal discrimination thresholds of individuals with ASD as measured by different measures. The somatosensory temporal discrimination (STD) test measures the threshold at which an individual can temporally discriminate multiple tactile stimuli delivered in succession. We aimed to investigate tactile perception in ASD and hypothesized that children with ASD have impaired STD related to their subjective sensory symptoms and daily difficulties. Thirty adolescents with ASD and 30 typically developed subjects were recruited. The Childhood Autism Rating Scale, Strengths and Difficulties Questionnaire, and Adolescent/Adult Sensory Profile were implemented before STD evaluation. Average somatosensory detection (1.48 ± 0.42) and discrimination thresholds (112.70 ± 43.45) of the children with ASD were significantly higher (P = 0.010, P = 0.001, respectively) than those of the controls (1.18 ± 0.42, 79.95 ± 31.60, respectively). Sensory seeking scores of the ASD group (40.8 ± 7.60) were significantly lower (P = 0.024) than those of the control group (45.83 ± 9.17). However, the psychophsycal thresholds did not have any statistically significant relationships with subjective sensory symptoms or daily difficulties. This study demonstrates impaired sensory processing in ASD evaluated by STD and its lack of relationship with subjective sensory symptoms and daily difficulties. This psychophysical evidence of increased STD thresholds and decreased sensory seeking profile supports the disturbances in the regulation of sensory processing in ASD. LAY SUMMARY: Sensory differences are common in autism; however, there is no well-accepted method to measure them objectively. This study aims to investigate somatosensory differences and their relation with sensory and emotional/behavioral difficulties of children with autism. We show that autistic children have higher tactile discrimination thresholds and fewer sensory seeking behaviors. This supports the presence of impairments in sensory processing in autism. Measuring the sensory differences may help understanding clinical symptoms and neurobiological underpinings of autism. Autism Res 2021, 14: 656-667. © 2021 International Society for Autism Research and Wiley Periodicals LLC.

Affective touch experiences across the lifespan: Development of the Tactile Biography questionnaire and the mediating role of attachment style

The sense of touch develops early in life and becomes a determinant aspect of our personal narratives, providing crucial information about the world around us and playing a prominent role in affective and social interactions. In this study we aimed to explore whether individual differences in touch experiences across the lifespan are related to adult attachment styles and to perceived touch deprivation. For this we first developed an instrument, namely the Tactile Biography, to quantify individual differences in affective touch experiences throughout life. Secondly, we performed a set of regressions models and a mediation analysis to investigate the role of attachment in relation to both the tactile history and perceived touch deprivation. We found that experiences of affective touch during childhood and adolescence seem to be closely associated with adult attachment styles and adult social touch experiences. Avoidant attachment appears to serve as a mediator in the relationship between earlier (childhood/adolescent) and later (adult) affective touch experiences, as well as between earlier affective touch experiences and perceived touch deprivation. These findings offer further support to existing literature, providing novel insights for the fields of social affective touch and attachment research.

Oxytocin increases the pleasantness of affective touch and orbitofrontal cortex activity independent of valence

Touch plays a crucial role in affiliative behavior and social communication. The neuropeptide oxytocin is released in response to touch and may act to facilitate the rewarding effects of social touch. However, no studies to date have determined whether oxytocin facilitates behavioral or neural responses to non-socially administered affective touch and possible differential effects of touch valence. In a functional MRI experiment using a randomized placebo-controlled, within-subject design in 40 male subjects we investigated the effects of intranasal oxytocin (24IU) on behavioral and neural responses to positive, neutral and negative valence touch administered to the arm via different types of materials at a frequency aimed to optimally stimulate C-fibers. Results showed that oxytocin significantly increased both the perceived pleasantness of touch and activation of the orbitofrontal cortex independent of touch valence. The effects of OT on touch-evoked orbitofrontal activation were also positively associated with basal oxytocin concentrations in blood. Additionally, anterior insula activity and the functional connectivity between the amygdala and right anterior insula were enhanced only in response to negative valence touch. Overall, the present study provides the first evidence that oxytocin may facilitate the rewarding effects of all types of touch, irrespective of valence.

Cortical signatures in behaviorally clustered autistic traits subgroups: a population-based study

Extensive heterogeneity in autism spectrum disorder (ASD) has hindered the characterization of consistent biomarkers, which has led to widespread negative results. Isolating homogenized subtypes could provide insight into underlying biological mechanisms and an overall better understanding of ASD. A total of 1093 participants from the population-based "Healthy Brain Network" cohort (Child Mind Institute in the New York City area, USA) were selected based on score availability in behaviors relevant to ASD, aged 6-18 and IQ >= 70. All participants underwent an unsupervised clustering analysis on behavioral dimensions to reveal subgroups with ASD traits, identified by the presence of social deficits. Analysis revealed three socially impaired ASD traits subgroups: (1) high in emotionally dysfunctional traits, (2) high in ADHD-like traits, and (3) high in anxiety and depressive symptoms. 527 subjects had good quality structural MRI T1 data. Site effects on cortical features were adjusted using the ComBat method. Neuroimaging analyses compared cortical thickness, gyrification, and surface area, and were controlled for age, gender, and IQ, and corrected for multiple comparisons. Structural neuroimaging analyses contrasting one combined heterogeneous ASD traits group against controls did not yield any significant differences. Unique cortical signatures, however, were observed within each of the three individual ASD traits subgroups versus controls. These observations provide evidence of ASD traits subtypes, and confirm the necessity of applying dimensional approaches to extract meaningful differences, thus reducing heterogeneity and paving the way to better understanding ASD traits.

Reduced task-dependent modulation of functional network architecture for positive versus negative affective touch processing in autism spectrum disorders

Individuals with autism spectrum disorders (ASD) experience impairments in social communication and interaction, and often show difficulties with receiving and offering touch. Despite the high prevalence of abnormal reactions to touch in ASD, and the importance of touch communication in human relationships, the neural mechanisms underlying atypical touch processing in ASD remain largely unknown. To answer this question, we provided both pleasant and unpleasant touch stimulation to male adults with and without ASD during functional neuroimaging. By employing generalized psychophysiological interaction analysis combined with an independent component analysis approach, we characterize stimulus-dependent changes in functional connectivity patterns for processing two tactile stimuli that evoke different emotions (i.e., pleasant vs. unpleasant touch). Results reveal that neurotypical male adults showed extensive stimulus-sensitive modulations of the functional network architecture in response to the different types of touch, both at the level of brain regions and large-scale networks. Conversely, far fewer stimulus-sensitive modulations were observed in the ASD group. These aberrant functional connectivity profiles in the ASD group were marked by hypo-connectivity of the parietal operculum and major pain networks and hyper-connectivity between the semantic and limbic networks. Lastly, individuals presenting more social deficits and a more negative attitude towards social touch showed greater hyper-connectivity between the limbic and semantic networks. These findings suggest that reduced stimulus-related modulation of this functional network architecture is associated with abnormal processing of touch in ASD.

Individual Variability of Pleasantness Ratings to Stroking Touch Over Different Velocities

Many studies have investigated the perception of tactile pleasantness over a range of stroking velocities. On average, pleasantness is low at slow (e.g. 0.3 cm/s) and fast (e.g. 30 cm/s) stroking velocities, but is rated highest at velocities between 1 and 10 cm/s. On a group level, this results in an inverted-U shape pleasantness ratings curve, which is described statistically by a negative quadratic equation. We reanalyzed the data from five earlier studies to investigate whether the inverted-U shape pleasantness curve at the group level is also present at the level of the individual, - a precondition for using tactile pleasantness perception as a diagnostic marker. We pooled the data from five studies with a total of 127 participants. Each study included a 'standard condition' of stroking on the dorsal forearm over different velocities (0.3, 1, 3, 10, 30 cm/s) and participants rated the pleasantness. Factors other than stroking velocity were also varied in these studies. On the whole-group level and in each study, pleasantness ratings produced a significant negative quadratic pleasantness curve over the stroking velocities. In individual participants, ratings varied greatly and only 42% of the participants showed a significant negative quadratic curve. The steepness of the inverted-U correlated only moderately across other experimental conditions, showing that the experimental circumstances can influence pleasantness ratings. Our findings have important implications for future work, where differences in the tactile pleasantness curve should not be used to predict or diagnose issues at an individual level.

The body comes first. Embodied reparation and the co-creation of infant bodily-self

During infancy relational experiences of body-to-body exchanges (i.e., embodied interactions) contribute to the infant's bodily perception. Early embodied interactions are based on countless multimodal reciprocal exchanges, in which mother and infant contribute to interpersonal rhythmic cycles of co-regulation (i.e., attunement). However, it remains unclear how infants and their mothers actually accomplish attunement in their exchanges. Interactions between mothers and their infants typically fluctuate between attuned and misattuned states and recovery attunement states by a process called 'reparation'. Here, we discuss recent neuroscientific evidence that provides insight into the mechanisms underpinning the concepts of attunement and misattunement in early embodied interactions. We propose that a process of embodied reparation might be achieved within the dyad through tactile contact behaviors (e.g., skin-to-skin, affectionate touch) and maternal interoceptive sensitivity (i.e., ability to perceive internal input about the state of one's own body). We describe how these elements that mothers provide during embodied interactions with their infants, might contribute not only to bodily attunement, but also to co-create the infant bodily-self.

Unique Relationships Between Autistic Traits and Visual, Auditory, and Tactile Sensory Thresholds in Typically Developing Adults

Autism spectrum disorder (ASD) refers to neurodevelopmental disorders characterized by symptoms such as social deficits and restricted interests and behavior. Several studies have investigated specific sensory processing in relation to ASD traits. However, findings appear to be inconsistent and inconclusive because of variation in ASD traits among participants and differences in the tasks adopted. In this study, we investigated relationships between sensory thresholds in visual, auditory, and tactile modalities and various ASD traits to account for individual variability of traits in typically developing adults using the same experimental tasks. We estimated detection and discrimination thresholds for brightness, sound pressure, and vibrotactile stimulus strength. We also estimated the degree of ASD traits in each participant with a questionnaire. We found that higher tactile detection and visual discrimination thresholds were related to ASD traits in difficulty of communication. A lower tactile discrimination threshold and higher visual detection threshold was also related to the ASD trait of strong focus of attention. These findings suggest the existence of unique relationships between particular low-level sensory processing and specific ASD traits, indicating that irregularities in sensory processing may underlie variation in ASD traits.

Update of a Meta-analysis of Sensory Symptoms in ASD: A New Decade of Research

This meta-analysis updated evidence regarding sensory over-responsivity (SOR), under-responsivity (SUR) and seeking symptoms in individuals with autism spectrum disorders (ASDs) relative to typical controls and those with other conditions. Fifty-five questionnaire studies included 4606 individuals with ASD. Moderators tested were age, IQ, male ratio, matching group, and self-report. Compared to typical controls, effect size was large and significant for SOR, SUR, and Seeking but heterogeneous. For Seeking, age, IQ and self-report were significant moderators. Compared with developmental disorders (DDs) groups, effect size was significantly positive for SOR and Seeking; whereas compared with other clinical groups, only SOR was significant. These findings highlight the core nature of sensory symptoms in ASD and particularly SOR. Explanatory factors are yet to be revealed.

Intact neural representations of affective meaning of touch but lack of embodied resonance in autism: a multi-voxel pattern analysis study

Background

Humans can easily grasp the affective meaning of touch when observing social interactions. Several neural systems support this ability, including the theory of mind (ToM) network and the somatosensory system linked to embodied resonance, but it is unclear how these systems are affected in autism spectrum disorder (ASD). Individuals with ASD exhibit impairments in the use of nonverbal communication such as social and reciprocal touch. Despite the importance of touch in social communication and the reported touch aversion in ASD, surprisingly little is known about the neural systems underlying impairments in touch communication in ASD.

Methods

The present study applies a dynamic and socially meaningful stimulus set combined with functional magnetic resonance imaging (fMRI) to pinpoint atypicalities in the neural circuitry underlying socio-affective touch observation in adults with ASD. Twenty-one adults with ASD and 21 matched neurotypical adults evaluated the valence and arousal of 75 video fragments displaying touch interactions. Subsequently, they underwent fMRI while watching the same videos. Using multi-voxel pattern analysis (MVPA) and multiple regression analysis, we examined which brain regions represent the socio-affective meaning of observed touch. To further understand the brain-behavior relationship, we correlated the strength of affective representations in the somatosensory cortex with individuals' attitude towards social touch in general and with a quantitative index of autism traits as measured by the Social Responsiveness Scale.

Results

Results revealed that the affective meaning of touch was well represented in the temporoparietal junction, a core mentalizing area, in both groups. Conversely, only the neurotypical group represented affective touch in the somatosensory cortex, a region involved in self-experienced touch. Lastly, irrespective of the group, individuals with a more positive attitude towards receiving, witnessing, and providing social touch and with a higher score on social responsivity showed more differentiated representations of the affective meaning of touch in these somatosensory areas.

Conclusions

Together, our findings imply that male adults with ASD show intact cognitive understanding (i.e., "knowing") of observed socio-affective touch interactions, but lack of spontaneous embodied resonance (i.e., "feeling").

Self-reported Sensory Hypersensitivity Moderates Association Between Tactile Psychophysical Performance and Autism-Related Traits in Neurotypical Adults

Atypical responses to tactile stimulation have been linked to core domains of dysfunction in individuals with autism spectrum disorder (ASD) and phenotypic traits associated with ASD in neurotypical individuals. We investigated (a) the extent to which two psychophysically derived measures of tactile sensitivity-detection threshold and dynamic range-relate to traits associated with ASD and (b) whether those relations vary according to the presence of self-reported sensory hypersensitivities in neurotypical individuals. A narrow dynamic range was associated with increased autism-related traits in individuals who reported greater sensory hypersensitivity. In contrast, in individuals less prone to sensory hypersensitivity, a narrow dynamic range was associated with reduced autism-related traits. Findings highlight the potential importance of considering dynamic psychophysical metrics in future studies.

Ayres Theories of Autism and Sensory Integration Revisited: What Contemporary Neuroscience Has to Say

Abnormal sensory-based behaviors are a defining feature of autism spectrum disorders (ASD). Dr. A. Jean Ayres was the first occupational therapist to conceptualize Sensory Integration (SI) theories and therapies to address these deficits. Her work was based on neurological knowledge of the 1970’s. Since then, advancements in neuroimaging techniques make it possible to better understand the brain areas that may underlie sensory processing deficits in ASD. In this article, we explore the postulates proposed by Ayres (i.e., registration, modulation, motivation) through current neuroimaging literature. To this end, we review the neural underpinnings of sensory processing and integration in ASD by examining the literature on neurophysiological responses to sensory stimuli in individuals with ASD as well as structural and network organization using a variety of neuroimaging techniques. Many aspects of Ayres’ hypotheses about the nature of the disorder were found to be highly consistent with current literature on sensory processing in children with ASD but there are some discrepancies across various methodological techniques and ASD development. With additional characterization, neurophysiological profiles of sensory processing in ASD may serve as valuable biomarkers for diagnosis and monitoring of therapeutic interventions, such as SI therapy.

Higher Tactile Temporal Resolution as a Basis of Hypersensitivity in Individuals with Autism Spectrum Disorder

Many individuals with autism spectrum disorder (ASD) have symptoms of sensory hypersensitivity. Several studies have shown high individual variations in temporal processing of tactile stimuli. We hypothesized that these individual differences are linked to differences in hyper-reactivity among individuals with ASD. Participants performed two tasks as to vibrotactile stimuli: One is a temporal order judgement task, and another is a detection task. We found that individuals with ASD with higher temporal resolution tended to have more severe hypersensitivity symptoms. In contrast, the tactile detection threshold/sensitivity were related to the severities of stereotyped behaviour and restricted interests, rather than to hypersensitivity. Our findings demonstrate that higher temporal resolution to sensory stimuli may contribute to sensory hypersensitivity in individuals with ASD.

A longitudinal study of parent-reported sensory responsiveness in toddlers at-risk for autism

BACKGROUND

Atypical sensory responsivity and sensory interests are now included in the DSM 5 diagnostic criteria for autism spectrum disorder (ASD) under the broad domain of restricted and repetitive behavior (RRB). However, relatively little is known about the emergence of sensory-related features and their relation to conventionally defined RRB in the first years of life.

METHODS

Prospective, longitudinal parent-report data using the Sensory Experiences Questionnaire (SEQ) were collected for 331 high-risk toddlers (74 of whom met diagnostic criteria for ASD at age 2) and 135 low-risk controls. Longitudinal profiles for SEQ scores were compared between groups across ages 12-24 months. Associations between SEQ measures and measures of RRB subtypes (based on the Repetitive Behavior Scale, Revised) were also examined.

RESULTS

Longitudinal profiles for all SEQ scores significantly differed between groups. SEQ scores were elevated for the ASD group from age 12 months, with differences becoming more pronounced across the 12-24 month interval. At both 12 and 24 months, most measures derived from the SEQ were significantly associated with all subtypes of RRB.

CONCLUSIONS

These findings suggest that differences in sensory responsivity may be evident in high-risk infants later diagnosed with ASD in early toddlerhood, and that the magnitude of these differences increases over the second year of life. The high degree of association between SEQ scores and RRB supports the conceptual alignment of these features but also raises questions as to explanatory mechanisms.

Gentle Handling Attenuates Innate Defensive Responses to Visual Threats

Innate defensive responses to threats are essential for animal survival. The complexity and variability of innate defensive behaviors can be due to individual experiences, environmental factors, and internal states. However, it is not completely understood if the gentle handling involved in sensory processing affects innate defensive responses to visual threats. Here, we report attenuation of innate defensive responses after gentle handling accompanied by de-excitation of the intermediate layer (IL) and deep layer (DL) of the superior colliculus (SC) but not of the superficial layer (SL). Our theoretical analysis of the c-Fos network revealed an increased correlation in module 1, which maybe generally functionally associated with fear emotional, a decreased correlation in module 2, which maybe generally functionally associated with sensory processing. The IL of the SC appeared to have the highest correlation with the two modules. We verified the dynamic activities of the IL of SC in response to overhead looming stimulus using fiber photometry. Retrograde labeling of 18 regions of interest (ROIs) showed that the IL received significant inputs from the cortical areas, thalamus, hypothalamus, and brainstem. These data suggest the sensory processing involved in the modulatory roles of the SC in innate fear processing.

Distributed Intrinsic Functional Connectivity Patterns Predict Diagnostic Status in Large Autism Cohort

Diagnosis of autism spectrum disorder (ASD) currently relies on behavioral observations because brain markers are unknown. Machine learning approaches can identify patterns in imaging data that predict diagnostic status, but most studies using functional connectivity MRI (fcMRI) data achieved only modest accuracies of 60-80%. We used conditional random forest (CRF), an ensemble learning technique protected against bias from feature correlation (which exists in fcMRI matrices). We selected 252 low-motion resting-state functional MRI scans from the Autism Brain Imaging Data Exchange, including 126 typically developing (TD) and 126 ASD participants, matched for age, nonverbal IQ, and head motion. A matrix of functional connectivities between 220 functionally defined regions of interest was used for diagnostic classification. In several runs, we achieved accuracies of 92-99% for classifiers with >300 features (most informative connections). Features, including pericentral somatosensory and motor regions, were disproportionately informative. Findings differed partially from a previous study in the same sample that used feature selection with random forest (which is biased by feature correlations). External validation in a smaller in-house data set, however, achieved only 67-71% accuracy. The large number of features in optimal models can be attributed to etiological heterogeneity under the clinical ASD umbrella. Lower accuracy in external validation is expected due to differences in unknown composition of ASD variants across samples. High accuracy in the main data set is unlikely due to noise overfitting, but rather indicates optimized characterization of a given cohort.

Factors influencing the severity of behavioral phenotype in autism spectrum disorders: Implications for research

The phenotypic heterogeneity of Autism Spectrum Disorders (ASD) presents particular research challenges in the assessment of symptom severity, while the standardized Autism Diagnostic Observation Schedule (ADOS) scores present a severity metric, namely calibrated severity scores (CSS) that are relatively impervious to individual characteristics. To date, no studies have examined the convergent validity of CSS in Chinese sample populations. The present study investigated the validity of the ADOS-CSS using a sample of 321 children aged 2-18 years with ASD, and developed upon existing literature examining the influence of non-ASD-specific characteristics on other types of measures including Autism Diagnostic Interview-Revised (ADI-R), Social Responsiveness Scale (SRS), and Vineland Adaptive Behavior Scales (VABS). As expected, the findings revealed that the CSS were less influenced than ADOS-RAW scores by the demographic and developmental-level variables. Moreover, compared to the ADOS-CSS, the ADI-R, SRS and VABS were still strongly correlated with confounding factors, such as chronological age, intelligence quotients, and language-level. The results of this study corroborate the utilization of CSS as a more valid indicator of ASD severity than raw scores from ADOS and other instruments.

Touch Processing and Social Behavior in ASD

Abnormal patterns of touch processing have been linked to core symptoms in ASD. This study examined the relation between tactile processing patterns and social problems in 44 children and adolescents with ASD, aged 6-14 (M = 8.39 ± 2.35). Multiple linear regression indicated significant associations between touch processing and social problems. No such relationships were found for social problems and autism severity. Within touch processing, patterns of hyper-responsiveness and hypo-responsiveness best predicted social problems, whereas sensory-seeking did not. These results support that atypical touch processing in individuals with ASD might be contributing to the social problems they present. Moreover, it the need to explore more in depth the contribution of sensory features to the ASD phenotype.

Altered reward system reactivity for personalized circumscribed interests in autism

Background

Neurobiological research in autism spectrum disorders (ASD) has paid little attention on brain mechanisms that cause and maintain restricted and repetitive behaviors and interests (RRBIs). Evidence indicates an imbalance in the brain’s reward system responsiveness to social and non-social stimuli may contribute to both social deficits and RRBIs. Thus, this study’s central aim was to compare brain responsiveness to individual RRBI (i.e., circumscribed interests), with social rewards (i.e., social approval), in youth with ASD relative to typically developing controls (TDCs).

Methods

We conducted a 3T functional magnetic resonance imaging (fMRI) study to investigate the blood-oxygenation-level-dependent effect of personalized circumscribed interest rewards versus social rewards in 39 youth with ASD relative to 22 TDC. To probe the reward system, we employed short video clips as reinforcement in an instrumental incentive delay task. This optimization increased the task’s ecological validity compared to still pictures that are often used in this line of research.

Results

Compared to TDCs, youth with ASD had stronger reward system responses for CIs mostly within the non-social realm (e.g., video games) than social rewards (e.g., approval). Additionally, this imbalance within the caudate nucleus’ responsiveness was related to greater social impairment.

Conclusions

The current data support the idea of reward system dysfunction that may contribute to enhanced motivation for RRBIs in ASD, accompanied by diminished motivation for social engagement. If a dysregulated reward system indeed supports the emergence and maintenance of social and non-social symptoms of ASD, then strategically targeting the reward system in future treatment endeavors may allow for more efficacious treatment practices that help improve outcomes for individuals with ASD and their families.

Electronic supplementary material

The online version of this article (10.1186/s13229-018-0195-7) contains supplementary material, which is available to authorized users.