Preference for biological motion is reduced in ASD: implications for clinical trials and the search for biomarkers

The Selective Social Attention task in children with autism spectrum disorder: Results from the Autism Biomarkers Consortium for Clinical Trials (ABC-CT) feasibility study

The Selective Social Attention (SSA) task is a brief eye-tracking task involving experimental conditions varying along socio-communicative axes. Traditionally the SSA has been used to probe socially-specific attentional patterns in infants and toddlers who develop autism spectrum disorder (ASD). This current work extends these findings to preschool and school-age children. Children 4- to 12-years-old with ASD (N = 23) and a typically-developing comparison group (TD; N = 25) completed the SSA task as well as standardized clinical assessments. Linear mixed models examined group and condition effects on two outcome variables: percent of time spent looking at the scene relative to scene presentation time (%Valid), and percent of time looking at the face relative to time spent looking at the scene (%Face). Age and IQ were included as covariates. Outcome variables' relationships to clinical data were assessed via correlation analysis. The ASD group, compared to the TD group, looked less at the scene and focused less on the actress' face during the most socially-engaging experimental conditions. Additionally, within the ASD group, %Face negatively correlated with SRS total T-scores with a particularly strong negative correlation with the Autistic Mannerism subscale T-score. These results highlight the extensibility of the SSA to older children with ASD, including replication of between-group differences previously seen in infants and toddlers, as well as its ability to capture meaningful clinical variation within the autism spectrum across a wide developmental span inclusive of preschool and school-aged children. The properties suggest that the SSA may have broad potential as a biomarker for ASD.

Hysteresis reveals a happiness bias effect in dynamic emotion recognition from ambiguous biological motion

Considering the nonlinear dynamic nature of emotion recognition, it is believed to be strongly dependent on temporal context. This can be investigated by resorting to the phenomenon of hysteresis, which features a form of serial dependence, entailed by continuous temporal stimulus trajectories. Under positive hysteresis, the percept remains stable in visual memory (persistence) while in negative hysteresis, it shifts earlier (adaptation) to the opposite interpretation. Here, we asked whether positive or negative hysteresis occurs in emotion recognition of inherently ambiguous biological motion, while testing for the controversial debate of a negative versus positive emotional bias. Participants (n = 22) performed a psychophysical experiment in which they were asked to judge stimulus transitions between two emotions, happiness and sadness, from an actor database, and report perceived emotion across time, from one emotion to the opposite as physical cues were continuously changing. Our results reveal perceptual hysteresis in ambiguous emotion recognition, with positive hysteresis (visual persistence) predominating. However, negative hysteresis (adaptation/fatigue) was also observed in particular in the direction from sadness to happiness. This demonstrates a positive (happiness) bias in emotion recognition in ambiguous biological motion recognition. Finally, the interplay between positive and negative hysteresis suggests an underlying competition between visual persistence and adaptation mechanisms during ambiguous emotion recognition.

Does the current state of biomarker discovery in autism reflect the limits of reductionism in precision medicine? Suggestions for an integrative approach that considers dynamic mechanisms between brain, body, and the social environment

Over the past decade, precision medicine has become one of the most influential approaches in biomedical research to improve early detection, diagnosis, and prognosis of clinical conditions and develop mechanism-based therapies tailored to individual characteristics using biomarkers. This perspective article first reviews the origins and concept of precision medicine approaches to autism and summarises recent findings from the first "generation" of biomarker studies. Multi-disciplinary research initiatives created substantially larger, comprehensively characterised cohorts, shifted the focus from group-comparisons to individual variability and subgroups, increased methodological rigour and advanced analytic innovations. However, although several candidate markers with probabilistic value have been identified, separate efforts to divide autism by molecular, brain structural/functional or cognitive markers have not identified a validated diagnostic subgroup. Conversely, studies of specific monogenic subgroups revealed substantial variability in biology and behaviour. The second part discusses both conceptual and methodological factors in these findings. It is argued that the predominant reductionist approach, which seeks to parse complex issues into simpler, more tractable units, let us to neglect the interactions between brain and body, and divorce individuals from their social environment. The third part draws on insights from systems biology, developmental psychology and neurodiversity approaches to outline an integrative approach that considers the dynamic interaction between biological (brain, body) and social mechanisms (stress, stigma) to understanding the origins of autistic features in particular conditions and contexts. This requires 1) closer collaboration with autistic people to increase face validity of concepts and methodologies; (2) development of measures/technologies that enable repeat assessment of social and biological factors in different (naturalistic) conditions and contexts, (3) new analytic methods to study (simulate) these interactions (including emergent properties), and (4) cross-condition designs to understand which mechanisms are transdiagnostic or specific for particular autistic sub-populations. Tailored support may entail both creating more favourable conditions in the social environment and interventions for some autistic people to increase well-being.

Pupillometric measures of altered stimulus-evoked locus coeruleus-norepinephrine activity explain attenuated social attention in preschoolers with autism spectrum disorder

Attenuated social attention has been described as a reduced preference for social compared to geometric motion in preschoolers with autism spectrum disorder (ASD). The locus coeruleus-norpinephrine (LC-NE) system modulates sensory reactivity and is a promising underlying mechanism. LC-NE activity is indexed by a stimulus-evoked pupillary response (SEPR) and partially by a luminance-adaptation pupillary response (LAPR), which were both shown to be aberrant in ASD. We examined whether SEPR and LAPR explain an attenuated social motion preference. We applied pupillometry via video-based eye tracking in young children (18-65 months) with ASD (n = 57) and typically developing (TD) children (n = 39) during a preferential looking paradigm of competing social and geometric motion and a changing light condition paradigm. We found an attenuated social motion preference in the ASD compared to the TD group. This was accompanied by atypical pupillometry showing a smaller SEPR to social motion, a larger SEPR to geometric motion and a reduced LAPR to a dark screen. SEPR but not LAPR explained the group difference in social motion preference. An ASD diagnosis was statistically predicted by the social motion preference, while this effect was mediated by the inclusion of SEPR to geometric and social motion. Our findings suggest a decreased sensory reactivity to social and increased reactivity to non-social motion in ASD, which may concurrently contribute to an attenuated social attention. The LC-NE system is supported as a promising underlying mechanism of altered social attention in young children with ASD, while the specificity of findings remains to be addressed.

Social Attention: Developmental Foundations and Relevance for Autism Spectrum Disorder

The use of the term "social attention" (SA) in the cognitive neuroscience and developmental psychopathology literature has increased exponentially in recent years, in part motivated by the aim to understand the early development of autism spectrum disorder (ASD). Unfortunately, theoretical discussions around the term have lagged behind its various uses. Here, we evaluate SA through a review of key candidate SA phenotypes emerging early in life, from newborn gaze cueing and preference for face-like configurations to later emerging skills such as joint attention. We argue that most of the considered SA phenotypes are unlikely to represent unique socioattentional processes and instead have to be understood in the broader context of bottom-up and emerging top-down (domain-general) attention. Some types of SA behaviors (e.g., initiation of joint attention) are linked to the early development of ASD, but this may reflect differences in social motivation rather than attention per se. Several SA candidates are not linked to ASD early in life, including the ones that may represent uniquely socioattentional processes (e.g., orienting to faces, predicting others' manual action goals). Although SA may be a useful superordinate category under which one can organize certain research questions, the widespread use of the term without proper definition is problematic. Characterizing gaze patterns and visual attention in social contexts in infants at elevated likelihood of ASD may facilitate early detection, but conceptual clarity regarding the underlying processes at play is needed to sharpen research questions and identify potential targets for early intervention.

Modern Biomarkers for Autism Spectrum Disorder: Future Directions

Autism spectrum disorder is an increasingly prevalent neurodevelopmental disorder in the world today, with an estimated 2% of the population being affected in the USA. A major complicating factor in diagnosing, treating, and understanding autism spectrum disorder is that defining the disorder is solely based on the observation of behavior. Thus, recent research has focused on identifying specific biological abnormalities in autism spectrum disorder that can provide clues to diagnosis and treatment. Biomarkers are an objective way to identify and measure biological abnormalities for diagnostic purposes as well as to measure changes resulting from treatment. This current opinion paper discusses the state of research of various biomarkers currently in development for autism spectrum disorder. The types of biomarkers identified include prenatal history, genetics, neurological including neuroimaging, neurophysiologic, and visual attention, metabolic including abnormalities in mitochondrial, folate, trans-methylation, and trans-sulfuration pathways, immune including autoantibodies and cytokine dysregulation, autonomic nervous system, and nutritional. Many of these biomarkers have promising preliminary evidence for prenatal and post-natal pre-symptomatic risk assessment, confirmation of diagnosis, subtyping, and treatment response. However, most biomarkers have not undergone validation studies and most studies do not investigate biomarkers with clinically relevant comparison groups. Although the field of biomarker research in autism spectrum disorder is promising, it appears that it is currently in the early stages of development.