Neural Processing of Speech Sounds in ASD and First-Degree Relatives

Abstract

Background: Efficient neural encoding of sound plays a critical and widespread role in speech and language, and when impaired, may have reverberating effects on a range of communication skills. Autism spectrum disorder (ASD) is a condition involving impaired communication abilities, including atypical prosody (e.g., intonation modulation, rate, rhythm), in which atypical neural processing of speech has been implicated. Parallel patterns of communication differences have been noted in parents of individuals with ASD, who may exhibit subclinical language-related differences believed to reflect genetic liability to ASD. The present study investigated disruptions to neural processing of temporal and spectral (i.e., frequency/pitch) properties of speech sounds as a potential neurobiological mechanism underlying specific language-related impairments in ASD and related subclinical differences documented among first-degree relatives of individuals with ASD. Methods: Participants included individuals with ASD, their parents, and respective control groups. Group differences in temporal and spectral processing based on the neural FFR were assessed using MANCOVAs controlling for chronological age. Relationships between the FFR, pragmatic language ability, and receptive and expressive prosody skills were assessed using Pearson correlations. Familiality of the FFR in mother-child dyads were also examined using Pearson correlations.Results: Findings revealed inefficiencies in neural encoding of speech sounds in both individuals with ASD and their parents (specifically, increased neural noise and delayed neural processing of speech sounds), as well as a less robust neural representation of spectral properties of speech sounds in individuals with ASD. Associations between neural processing of speech sounds and language-related abilities were detected in both groups, along with evidence of familiality of neural pitch processing in the ASD family groups. Limitations: Additional investigation is necessary to determine whether relationships between FFR and pragmatic language and prosody extend to individuals with more severe language and/or cognitive impairments. Conclusions: Overall, results suggest atypical neural processing of speech sounds may constitute an important, heritable ingredient contributing to the ASD language phenotype and subclinical phenotypic expression of genetic liability in parents.

Childhood Academic Performance: A Potential Marker of Genetic Liability to Autism

“…Furthermore, the present study identified key associations that suggest differential parentchild relationships for mothers and fathers, where only mothers' BAP characteristics and childhood language abilities were related to siblings' language abilities. Indeed, a growing body of literature has suggested that the presence and quality of ASD endophenotypes differ among mothers and fathers, as do relationships between parent endophenotypes and their child's clinical behavioral presentation (33,43,83,(92)(93)(94). Consistent with the results reported here, several studies have found BAP traits in mothers, but not fathers, to be linked to child language abilities in individuals with ASD (34,83,92,93).…”

“…Such weaknesses in linguistic fluency and speech sound processing may have downstream impacts on functional language abilities such as pragmatic language skills. Deeper explorations of pragmatic phenotypes have also revealed discrepancies from controls in the acoustic characteristics of speech that are similar to those observed in ASD and characterized by differences in intonation, modulation of volume, rate of speech, and stress patterns (30,(41)(42)(43). Pragmatic language difficulties have further been evidenced among parents through subtle differences in narrative generation, characterized by decreased complexity and coherence, with overall narrative quality subject to context variability (40).…”

“…Subtle differences in language-related skills have been particularly notable in clinically unaffected relatives of individuals with ASD ranging from self and informant reported early language delays or literacy difficulties (38,39) and mechanistic differences in language processing and fluency (32,34,37), to more nuanced or complex features of pragmatics, including prosody, auditory processing, and narrative generation abilities (30,(40)(41)(42)(43). Several studies have demonstrated reduced fluency on tasks that tap into broader cognitive and linguistic processes that underly complex language among first-degree relatives (32)(33)(34)(35).…”

“…For instance, a study investigating links between eye movement and speech on a task that involves rapid naming of familiar objects (Rapid Automatized Naming, RAN), found slower naming times, and less fluid eye movement patterns during naming (e.g., frequent refixations to previous items) relative to controls, and associations between such patterns and characteristics of the BAP (34). The literature also suggests that speech sound processing is impacted in parents, including phonological processing weaknesses evidenced via difficulties with nonword repetition (37), as well as diminished neural representations of speech sounds and less efficient neural systems of audio-vocal feedback (37,42,43). Such weaknesses in linguistic fluency and speech sound processing may have downstream impacts on functional language abilities such as pragmatic language skills.…”

Heritability of Sound Processing Deficits in Autism: Neural Insights

“…Over the years, my team has published a few studies on auditory processing in autism and I have written about the topic here in Hearing Matters. 1,2 In a new study published in the Journal of Autism and Developmental Disorders 3, my colleagues down the hall at the Northwestern University Neurodevelopmental Disabilities Lab, headed by Dr. Molly Losh, teamed up with my Brainvolts Lab to look at sound processing not only in people with autism, but in parents of people with autism.…”