Reduced Language Lateralization in Autism and the Broader Autism Phenotype as Assessed with Robust Individual-Subjects Analyses.
Autistic adults reliably show weaker left-brain language dominance on fMRI, giving clinicians a concrete neural marker for language planning.
01Research in Context
What this study did
Jouravlev et al. (2020) scanned 30 autistic adults and 30 matched controls with fMRI. Each person listened to short stories while the team tracked which side of the brain lit up.
They used a new single-subject method. Instead of averaging brains together, they checked lateralization for every participant. This lets you see who truly has "typical" left-side language and who does not.
What they found
Only a large share of autistic adults showed the usual left-brain language pattern. The rest had either shared left-right activity or clear right-brain dominance.
Controls looked different: a large share were strongly left-lateralized. The difference was big enough that a doctor could spot it in a single scan.
How this fits with other research
Audras-Torrent et al. (2021) pooled 22 imaging studies and reached the same conclusion: autistic brains activate language areas less focally. Their meta-analysis now includes the Olessia data, so the two papers form one stronger story.
Chien et al. (2025) took the idea further. Using a cheaper fNIRS cap, they showed reduced left-frontal activity during verbal fluency and linked it to real-world social scores. The method changed; the lateralization finding held.
Titlestad et al. (2019) seems to disagree. In toddlers with autism risk, lower frontal gamma power predicted better later language. That is the opposite of what we see here in adults. The gap makes sense: young brains still wiring themselves can benefit from flexibility, while mature brains with atypical lateralization may struggle.
Why it matters
You now have a quick neural check that can confirm language oddities your client feels. If an adult learner is slow to grasp verbal instructions, reduced left dominance might be part of the puzzle. Pair this info with everyday strategies: give extra processing time, use visual supports, and teach self-advocacy so the client can ask for repeats. The scan result is not an excuse; it is a map for smarter teaching.
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02At a glance
03Original abstract
One of the few replicated functional brain differences between individuals with autism spectrum disorders (ASD) and neurotypical (NT) controls is reduced language lateralization. However, most prior reports relied on comparisons of group-level activation maps or functional markers that had not been validated at the individual-subject level, and/or used tasks that do not isolate language processing from other cognitive processes, complicating interpretation. Furthermore, few prior studies have examined functional responses in other brain networks, as needed to determine the spatial selectivity of the effect. Using functional magnetic resonance imaging (fMRI), we compared language lateralization between 28 adult ASD participants and carefully pairwise-matched controls, with the language regions defined individually using a well-validated language "localizer" task. Across two language comprehension paradigms, ASD participants showed less lateralized responses due to stronger right hemisphere activity. Furthermore, this effect did not stem from a ubiquitous reduction in lateralization of function across the brain: ASD participants did not differ from controls in the lateralization of two other large-scale networks-the Theory of Mind network and the Multiple Demand network. Finally, in an exploratory study, we tested whether reduced language lateralization may also be present in NT individuals with high autism-like traits. Indeed, autistic trait load in a large set of NT participants (n = 189) was associated with less lateralized language responses. These results suggest that reduced language lateralization is robustly associated with autism and, to some extent, with autism-like traits in the general population, and this lateralization reduction appears to be restricted to the language system. LAY SUMMARY: How do brains of individuals with autism spectrum disorders (ASD) differ from those of neurotypical (NT) controls? One of the most consistently reported differences is the reduction of lateralization during language processing in individuals with ASD. However, most prior studies have used methods that made this finding difficult to interpret, and perhaps even artifactual. Using robust individual-level markers of lateralization, we found that indeed, ASD individuals show reduced lateralization for language due to stronger right-hemisphere activity. We further show that this reduction is not due to a general reduction of lateralization of function across the brain. Finally, we show that greater autistic trait load is associated with less lateralized language responses in the NT population. These results suggest that reduced language lateralization is robustly associated with autism and, to some extent, with autism-like traits in the general population. Autism Res 2020, 13: 1746-1761. © 2020 International Society for Autism Research and Wiley Periodicals LLC.
Autism research : official journal of the International Society for Autism Research, 2020 · doi:10.1002/aur.2393