Recapping some reasons why language is impaired in autism—and why degree of impairment correlates with autism severity

…With some implications for FC.

For infants to pick up language, they need to tune into it. That means preferentially tuning into the sounds of speech over non-speech sounds. Furthermore, they need to link speech sounds to meaning. This means tuning into the people who make those sounds—and, especially, to their eyes: where a speaker’s eyes are pointing indicates who the speaker is speaking to and/or what they speaking about. Speech, people, eyes: these are the key ingredients of social stimuli.

The less a child tunes into social stimuli, therefore, the less he or she will pick up language. The earlier in development this process is derailed, the greater the effects on language. At least eight studies of children 6 months and younger who are “at risk for autism”—that is, infants with an older autistic sibling—show that, in autism, this derailment begins early in development (bold-face added):

• Jones and Klin (2013): “infants later diagnosed with autism spectrum disorders (ASDs) exhibit mean decline in eye fixation from 2 to 6 months of age, a pattern not observed in infants who do not develop ASD.”

• Lloyd-Fox et al. (2013): “In a functional near-infrared spectroscopy study, infants aged 4–6 months at risk for autism showed less selective neural responses to social stimuli (auditory and visual) than low-risk controls…. Further, these differences closely resemble known patterns of neural atypicality in children and adults with autism.”

• Lloyd-Fox et al. (2017): “At 4-6 months, infants who went on to develop ASD at 3 years (N = 5) evidenced reduced activation to visual social stimuli relative to low-risk infants (N = 16) across inferior frontal (IFG) and posterior temporal (pSTS-TPJ) regions of the cortex. Furthermore, these infants also showed reduced activation to vocal sounds and enhanced activation to non-vocal sounds within left lateralized temporal (aMTG-STG/pSTS-TPJ) regions compared with low-risk infants and high-risk infants who did not develop ASD (N = 15).”

• Blanco et al. (2023): “infants at elevated likelihood of ASD showed attenuated responses to visual social stimuli in several cortical regions compared to infants at typical likelihood. Individual brain responses to visual social stimuli were associated with later autism traits... These outcomes support our previous observations showing atypical social brain responses in infants at elevated likelihood of ASD and align with later atypical brain responses to social stimuli observed in children and adults with ASD.” (Average age: 166 days).

• Blasi et al. (2015): “we used functional MRI to examine cortical sensitivity to auditory stimuli in infants at high familial risk for later emerging ASD (HR group, N = 15), and compared this to infants with no family history of ASD (LR group, N = 18)… Whereas LR infants showed early specialisation for human voice processing in right temporal and medial frontal regions, the HR infants did not. Similarly, LR infants showed stronger sensitivity than HR infants to sad vocalisations in the right fusiform gyrus and left hippocampus.”

• Jones et al. (2016): “High-risk infants who met criteria for ASD at 24 months showed shorter epochs of visual attention, faster but less prolonged neural activation to faces, and delayed sensitization responses (increases in looking) to faces at 6 months; these differences were less apparent at 12 months. These findings are consistent with disrupted engagement of sustained attention to social stimuli.”

• Chawarska et al. (2013): “6-month-old infants later diagnosed with ASD attended less to the social scene, and when they did look at the scene, they spent less time monitoring the actress in general and her face in particular.“

• Mastro et al. (2002):

  • “Fifteen home movies from the first 6 months of life of children who later received a diagnosis of ASD were compared with home movies of 15 normal children… found significant differences between the two groups for the items in the social attention and the social behavior areas; on the contrary, there were no differences in nonsocial attention.”

  • “The significant differences in items regarding interest in other persons confirm that children with ASD reveal a preference for nonsocial stimuli. Attention toward objects does not distinguish autistic from normal infants: object exploration, involving a few activity patterns, such as mouthing, waving, and banging, tended to be the same in both groups. This result probably means that attention is not implicated as a primary function but as an elective function only toward social stimuli. In short, infants with autism exhibited a specific qualitative pattern of attention, highly consistent with theories predicting that ASD children have a specific deficit in attending social stimuli.”

These patterns continue in older autistic children:

• Adamson et al. (2021). “Toddlers with ASD usually appeared aware of a new sound, often alerting to and orienting toward it. But compared to TD toddlers and toddlers with DD, they alerted and oriented less often to speech, a difference not found with the other sounds. Furthermore, toddlers with ASD were far less likely to spontaneously try to share the sound with the parents and to engage with the parent and the sound when parents tried to share it with them.” (Average age: 22.6 months).

• Kuhl et al. (2005): “In this study, we examined social and linguistic processing of speech in preschool children with autism spectrum disorder (ASD) and typically developing chronologically matched (TDCA) and mental age matched (TDMA) children. The social measure was an auditory preference test that pitted 'motherese' speech samples against non-speech analogs of the same signals. The linguistic measure was phonetic discrimination assessed with mismatch negativity (MMN), an event-related potential (ERP). As a group, children with ASD differed from controls by: (a) demonstrating a preference for the non-speech analog signals, and (b) failing to show a significant MMN in response to a syllable change.” (Average age: 45.31 months).

• Klin (1991): “[Participants] were given a choice between their mothers' speech and the noise of superimposed voices (a sound effect obtained in a busy canteen). Data were obtained utilizing a specially designed automated and computerized device which recorded the children's responses in their own homes. In contrast to comparison groups of mentally retarded and normally developing children who showed the expected strong preference for their mothers' speech, the autistic children actively preferred the alternative sound or showed a lack of preference for either audio segment. These results suggest that such abnormal reactions to speech are a feature of these children's overall disregard to people.” (Average age: 63.5 months.)

• Dawson et al (1998): “It was found that, compared to children with Down syndrome or typical development, children with autism more frequently failed to orient to all stimuli, and that this failure was much more extreme for social stimuli. Children with autism who oriented to social stimuli took longer to do so compared to the other two groups of children. Children with autism also exhibited impairments in shared attention.” (Average age: 64.6 months)

• Magreli et al. (2013): “While the two groups orient overtly to facial expressions, children with ASC do so to a lesser extent. Children with ASC differ importantly from TD children in the way they respond to speech cues, displaying little overt shifting of attention to speaking faces. When children with ASC orient to facial expressions, they show reaction times and first fixation lengths similar to those presented by TD children. However, children with ASC orient to speaking faces slower than TD children. These results support the hypothesis that individuals affected by ASC have difficulties processing complex social sounds and detecting intermodal correspondence between facial and vocal information.” “The impairment in social orienting to speech sound seems more severe than that observed with facial expressions.”  (Average age: 6.08 years).

• Čeponienė et al., (2003): “Acoustically matched simple tones, complex tones, and vowels were presented in separate oddball sequences, in which a repetitive "standard" sound was occasionally replaced by an infrequent ‘deviant’ sound differing from the standard in frequency (by 10%)… The sensory sound processing was intact in the high-functioning children with autism and was not affected by sound complexity or ‘speechness.’ In contrast, their involuntary orienting was affected by stimulus nature. It was normal to both simple- and complex-tone changes but was entirely abolished by vowel changes. These results demonstrate that, first, auditory orienting deficits in autism cannot be explained by sensory deficits and, second, that orienting deficit in autism might be speech-sound specific.” (Average age: 8.4 years).

• Lepistö et al. (2005): “involuntary orienting to sound changes, as reflected by the P3a ERP, was more impaired for speech than non-speech sounds in the children with autism, suggesting deficits particularly in social orienting. This has been proposed to be one of the earliest symptoms to emerge, with pervasive effects on later development.”

In addition, the degree to which these individuals tune in is correlated with autism severity, especially in terms of social symptoms like joint attention:

• Lloyd-Fox et al. (2017): “The degree of activation to both the visual and auditory stimuli correlated with parent-reported ASD symptomology in toddlerhood.”

• Blasi et al. (2015): “Also, in the HR group only, there was an association between each infant's degree of engagement during social interaction and the degree of voice sensitivity in key cortical regions.”

• Kuhl et al. (2005): “Participants with a strong preference for non-speech analogs tended to score lower on measures of initiating joint attention and expressive language.”

The connection to autism severity, together with the connection between attending to social stimuli and learning language, adds to the evidence I discussed in my last post: the evidence against the assumption that those who are most likely to be subjected to FC/RPM/S2C understand the sophisticated linguistic content that is attributed to them.

It’s worth noting, however, that one standard measure of autism severity, the ADOS Calibrated Severity Score (Gotham et al., 2009), controls for language levels, and thereby factors out the correlation between autism severity and language skill. To see the connection between language and autism severity, therefore, one must use raw, un-calibrated ADOS scores, or other measures—for example the various measures of social attention explored in the 15 studies reviewed here.

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REFERENCES:

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Blanco, B., Lloyd-Fox, S., Begum-Ali, J., Pirazzoli, L., Goodwin, A., Mason, L., Pasco, G., Charman, T., Jones, E. J. H., Johnson, M. H., & BASIS/STAARS Team (2023). Cortical responses to social stimuli in infants at elevated likelihood of ASD and/or ADHD: A prospective cross-condition fNIRS study. Cortex; a journal devoted to the study of the nervous system and behavior, 169, 18–34. https://doi.org/10.1016/j.cortex.2023.07.010

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