A Neurodevelopmental Shift in Reward Circuitry from Mother's to Nonfamilial Voices in Adolescence

Perception and adaptation of receptive prosody in autistic adolescents

A fundamental aspect of language processing is inferring others' minds from subtle variations in speech. The same word or sentence can often convey different meanings depending on its tempo, timing, and intonation-features often referred to as prosody. Although autistic children and adults are known to experience difficulty in making such inferences, the science remains unclear as to why. We hypothesize that detail-oriented perception in autism may interfere with the inference process if it lacks the adaptivity required to cope with the variability ubiquitous in human speech. Using a novel prosodic continuum that shifts the sentence meaning gradiently from a statement (e.g., "It's raining") to a question (e.g., "It's raining?"), we have investigated the perception and adaptation of receptive prosody in autistic adolescents and two groups of non-autistic controls. Autistic adolescents showed attenuated adaptivity in categorizing prosody, whereas they were equivalent to controls in terms of discrimination accuracy. Combined with recent findings in segmental (e.g., phoneme) recognition, the current results provide the basis for an emerging research framework for attenuated flexibility and reduced influence of contextual feedback as a possible source of deficits that hinder linguistic and social communication in autism.

Unveiling the development of human voice perception: Neurobiological mechanisms and pathophysiology

The human voice is a critical stimulus for the auditory system that promotes social connection, informs the listener about identity and emotion, and acts as the carrier for spoken language. Research on voice processing in adults has informed our understanding of the unique status of the human voice in the mature auditory cortex and provided potential explanations for mechanisms that underly voice selectivity and identity processing. There is evidence that voice perception undergoes developmental change starting in infancy and extending through early adolescence. While even young infants recognize the voice of their mother, there is an apparent protracted course of development to reach adult-like selectivity for human voice over other sound categories and recognition of other talkers by voice. Gaps in the literature do not allow for an exact mapping of this trajectory or an adequate description of how voice processing and its neural underpinnings abilities evolve. This review provides a comprehensive account of developmental voice processing research published to date and discusses how this evidence fits with and contributes to current theoretical models proposed in the adult literature. We discuss how factors such as cognitive development, neural plasticity, perceptual narrowing, and language acquisition may contribute to the development of voice processing and its investigation in children. We also review evidence of voice processing abilities in premature birth, autism spectrum disorder, and phonagnosia to examine where and how deviations from the typical trajectory of development may manifest.

Social motivation by self- and caregiver-report: Reporter concordance and social correlates among autistic and neurotypical youth

Differences in social motivation underlie the core social-communication features of autism according to several theoretical models, with decreased social motivation among autistic youth relative to neurotypical peers. However, research on social motivation often relies on caregiver reports and rarely includes firsthand perspectives of children and adolescents with autism. Furthermore, social motivation is typically assumed to be constant across social settings when it may actually vary by social context. Among a sample of 58 verbally fluent youth (8-13 years old; 22 with autism, 36 neurotypical), we examined correspondence between youth and caregiver reports of social motivation with peers and with adults, as well as diagnostic group differences and associations with social outcomes. Results suggest youth and caregivers provide overlapping but distinct information. Autistic youth had lower levels of social motivation relative to neurotypical youth, and reported relatively consistent motivation toward peers and adults. Youth self- and caregiver-report were correlated for motivation toward adults, but not toward peers. Despite low correspondence between self- and caregiver-reported motivation toward peers, autistic youths' self-report corresponded to caregiver-reported social skills and difficulties whereas caregiver-report of peer motivation did not. For neurotypical youth, self- and caregiver-reported motivation toward adults was correlated, but motivation by both reporters was largely independent of broader social outcomes. Findings highlight the unique value of self-report among autistic children and adolescents, and warrant additional work exploring the development, structure, and correlates of social motivation among autistic and neurotypical youth.

When the Brain Cares: Personal interests amplify engagement of language, self-reference, and reward regions in the brains of children with and without autism

Human language is shaped by individual experiences and interests. However, to study language in the brain, researchers use generic stimuli, avoiding the variable personal interests that typically animate language. Thus, it is unknown how personal interests affect language function in the brain. We conducted personalized functional magnetic resonance imaging (fMRI) in 20 typically-developing children as they listened to personalized narratives about their specific interest and non-personalized, generic narratives. Personally-interesting narratives amplified engagement of language regions, producing more consistent activation patterns across individuals - even though each narrative was unique - than the generic narratives. The personalized narratives also engaged self-reference and reward areas of the brain associated with motivation. Amplification of brain responses to personally-interesting narratives was also observed in 15 autistic children, a condition characterized by both intense specific interests and difficulties with communication. Here we show that personal interests significantly affect language processing in the human brain.

Amygdala circuit transitions supporting developmentally-appropriate social behavior

Social behaviors dynamically change throughout the lifespan alongside the maturation of neural circuits. The basolateral region of the amygdala (BLA), in particular, undergoes substantial maturational changes from birth throughout adolescence that are characterized by changes in excitation, inhibition, and dopaminergic modulation. In this review, we detail the trajectory through which BLA circuits mature and are influenced by dopaminergic systems to guide transitions in social behavior in infancy and adolescence using data from rodents. In early life, social behavior is oriented towards approaching the attachment figure, with minimal BLA involvement. Around weaning age, dopaminergic innervation of the BLA introduces avoidance of novel peers into rat pups' behavioral repertoire. In adolescence, social behavior transitions towards peer-peer interactions with a high incidence of social play-related behaviors. This transition coincides with an increasing role of the BLA in the regulation of social behavior. Adolescent BLA maturation can be characterized by an increasing integration and function of local inhibitory GABAergic circuits and their engagement by the medial prefrontal cortex (mPFC). Manipulation of these transitions using viral circuit dissection techniques and early adversity paradigms reveals the sensitivity of this system and its role in producing age-appropriate social behavior.

Acute intranasal oxytocin dose enhances social preference for parents over peers in male but not female peri-adolescent California mice (Peromyscus californicus)

Peri-adolescence is a critical developmental stage marked by profound changes in the valence of social interactions with parents and peers. We hypothesized that the oxytocin (OXT) and vasopressin (AVP) systems, known for influencing social behavior, would be involved in the maintenance and breaking of bonding behavior expressed by very early peri-adolescent males and females. In rodents, OXT is associated with mother-pup bonding and may promote social attachment to members of the natal territory. AVP, on the other hand, can act in contrasting ways to OXT and has been associated with aggression and territoriality. Specifically, we predicted that in peri-adolescent male and female juveniles of the biparental and territorial California mouse (Peromyscus californicus), a) OXT would increase the social preferences for the parents over unfamiliar age-matched peers (one male and one female), and b) AVP would break the parent-offspring bond and either increase time in the neutral chamber and/or approach to their unfamiliar and novel peers. We examined anxiety and exploratory behavior using an elevated plus maze and a novel object task as a control. Peri-adolescent mice were administered an acute intranasal (IN) treatment of 0.5 IU/kg IN AVP, 0.5 IU/kg IN OXT, or saline control; five minutes later, the behavioral tests were conducted. As predicted, we found that IN OXT enhanced social preference for parents; however, this was only in male and not female peri-adolescent mice. IN AVP did not influence social preference in either sex. These effects appear specific to social behavior and not anxiety, as neither IN OXT nor AVP influenced behavior during the elevated plus maze or novel object tasks. To our knowledge, this is the first evidence indicating that OXT may play a role in promoting peri-adolescent social preferences for parents and delaying weaning in males.

Exogenous testosterone administration is associated with differential neural response to unfamiliar peer's and own caregiver's voice in transgender adolescents

Changes in gonadal hormones during puberty are thought to potentiate adolescents' social re-orientation away from caregivers and towards peers. This study investigated the effect of testosterone on neural processing of emotional (vocal) stimuli by unfamiliar peers vs. parents, in transgender boys receiving exogenous testosterone as a gender-affirming hormone (GAH+) or not (GAH-). During fMRI, youth heard angry and happy vocal expressions spoken by their caregiver and an unfamiliar teenager. Youth also self-reported on closeness with friends and parents. Whole-brain analyses (controlling for age) revealed that GAH+ youth showed blunted neural response to caregivers' angry voices-and heightened response to unfamiliar teenage angry voices-in the anterior cingulate cortex. This pattern was reversed in GAH- youth, who also showed greater response to happy unfamiliar teenager vs. happy caregiver voices in this region. Blunted ACC response to angry caregiver voices-a pattern characteristic of GAH+ youth-was associated with greater relative closeness with friends over parents, which could index more "advanced" social re-orientation. Consistent with models of adolescent neurodevelopment, increases in testosterone during adolescence may shift the valuation of caregiver vs. peer emotional cues in a brain region associated with processing affective information.

Immune signaling in sex-specific neural and behavioral development: Adolescent opportunity

Sex differences in neural and behavioral development are integral to understanding neurodevelopmental, mental health, and neurodegenerative disorders. Much of the literature has focused on late prenatal and early postnatal life as a critical juncture for establishing sex-specific developmental trajectories, and data are now clear that immune signaling plays a central role in establishing sex differences early in life. Adolescence is another developmental period during which sex differences arise. However, we know far less about how immune signaling plays a role in establishing sex differences during adolescence. Herein, we review well-defined examples of sex differences during adolescence and then survey the literature to speculate how immune signaling might be playing a role in defining sex-specific adolescent outcomes. We discuss open questions in the literature and propose experimental design tenets that may assist in better understanding adolescent neurodevelopment.