Phonological processing in first‐degree relatives of individuals with autism: An fMRI study

Abstract

Autism spectrum disorders (ASD) are complex neurodevelopmental disorders. Twin studies have provided heritability estimates as high as 90% for idiopathic ASD. Further evidence for the spectrum’s heritability is provided by the presence of the broad autism phenotype (BAP) in unaffected first-degree relatives. Language ability, specifically phonological processing, is proposed to be a core BAP trait. To date, however, no functional neuroimaging investigations of phonological processing in relatives of individuals with ASD have been undertaken. We conducted a functional magnetic resonance imaging (fMRI) study in parents of children with ASD utilizing a priming task probing implicit phonological processing. In our condition that placed heavier demands on phonological recoding, parents exhibited greater hemodynamic responses than controls in a network of cortical regions involved in phonological processing. Across conditions, parents exhibited enhanced priming-induced response suppression suggesting compensatory neural processing. A nonword repetition test used in previous studies of relatives was also administered. Correlations between this measure and our functional measures also suggested compensatory processing in parents. Regions exhibiting atypical responses in parents included regions previously implicated in the spectrum’s language impairments and found to exhibit structural abnormalities in a parent study. These results suggest a possible neurobiological substrate of the phonological deficits proposed to be a core BAP trait. However, these results should be considered preliminary. No previous fMRI study has investigated phonological processing in ASD, so replication is required. Furthermore, interpretation of our fMRI results is limited by the fact that the parent group failed to exhibit behavioral evidence of phonological impairments.

Shared Neuroanatomical Substrates of Impaired Phonological Working Memory Across Reading Disability and Autism

“…Performance on all these tasks reflects the ability to maintain and manipulate auditory verbal or phonological information in short-term memory (e.g., 49). Such PWM deficits have been well documented in separate studies of children with reading disability (6, 50-52) or ASD (8, 11, 16). Our results show directly that a similar impairment of PWM is shared across poor readers and the age-, IQ-, and gender-matched children with ASD.…”

“…Children with ASD, particularly those with broader language impairments, have also shown impaired phonological awareness and verbal short-term memory (8-11). Moreover, atypical verbal short-term memory was found among unaffected first-degree relatives, which indicates that impaired PWM is a prominent feature of the broader autism phenotype (16). …”

Phonological Working Memory for Words and Nonwords in Cerebral Cortex

“…Children and adults who stutter also appear to have deficits in phonological working memory that may be independent of speech fluency (Anderson, Wagovich, & Hall, 2006;Byrd, McGill, & Usler, 2015;Hakim & Ratner, 2004). In autism, too, there is a pronounced impairment in phonological working memory (Kjelgaard & Tager-Flusberg, 2001), which appears to extend even to first-degree family members evincing the broad autism phenotype (Wilson et al, 2013).…”

Cognitive Functioning in the Broad Autism Phenotype

“…Consequently, Wilson and associates (2013) proposed that phonological processing differences in the brain appear to be a basic feature of the BAP. However, similar to Losh et al (2012), Wilson et al (2013) indicated that replication of their findings are necessary before any firm conclusions can be drawn.…”

“…More recently, Wilson et al (2013) claimed that deficient phonological processing is "a core BAP trait" (p. 1447). They explored this supposition by using an fMRI to scan the brains of parents of children with ASD and control participants.…”