Can an MRI show a difference in the brain of a nonverbal autistic vs. a speaking individual?
Nonverbal autism isn’t a choice; it’s Broca’s area not working properly.
Broca’s area is one of the brain regions most closely tied to spoken language.
It sits in the left frontal region and orchestrates speech production — not just single words, but sentence structure, and expressive and narrative language.
Because nonverbal autism involves limited or absent speech, researchers have long questioned whether Broca’s area looks different on MRI in this population.
We take the ability to talk, even just to say our name, for granted.
For autistics who can’t talk at all or who on occasion can utter a single simple word such as “Hi” or “No,” the neuro-path for speech is severely impaired.
MRI and the Brain
MRI allows researchers to examine brain structure, including size, shape, thickness and symmetry between the left and right hemispheres.
Some MRI imaging studies also examine connectivity, or how strongly different brain regions communicate.
What MRI can’t do is directly explain why someone can or just can’t form words, let alone a sentence.
Language development depends on multiple brain systems working together over time, not on one isolated region.
That distinction is especially important in autism, where brain development follows many different paths.
Structural Differences in Broca’s Area
Several structural MRI studies have found atypical patterns in Broca’s region among those with significant language impairment.
One frequently cited study (Foundas, et al, Journal of Speech, Language, and Hearing Research, 2004), found that kids with autism and language impairment showed a reversal of typical Broca’s area asymmetry.
Instead of being larger on the left, Broca’s area was larger on the right.
However, the same asymmetry pattern was also seen in kids with specific language impairment who did not have autism.
This suggests the finding is related to language development rather than autism itself.
Later studies expanded on this. Ecker et al (Brain, 2013), reported atypical cortical thickness patterns in frontal language regions in autism.
These differences varied widely across individuals and did not map cleanly onto verbal ability alone.
In short, some nonverbal autistics show structural differences in Broca’s area on MRI, but many do not.
Connectivity and Structure
More recent research points to connectivity as a stronger factor than size or shape.
First of all, a functional MRI study by Just et al (Brain, 2004), found reduced coordination between frontal and temporal language regions in autistic people.
Broca’s area was present, but it communicated less efficiently with other parts of the language network.
More recently, though, Zhou and colleagues reported altered connectivity between Broca’s area and subcortical regions in a 2022 Human Brain Mapping study.
These connectivity patterns were more closely related to language ability than to autism diagnosis itself.
This suggests that Broca’s area may be structurally intact — but functionally less integrated into the broader language system in some nonverbal autistic individuals.
Early Brain Development and Language Outcomes
Infant and toddler MRI studies offer additional insight.
Hazlett et al (Nature, 2017), showed that early brain overgrowth patterns in autism can affect frontal regions associated with language.
However, these early differences did not reliably predict which children would later turn out to be nonverbal.
Similarly, a longitudinal study led by Lombardo (Biological Psychiatry, 2015) found that developmental trajectories mattered more than single MRI snapshots when it came to predicting language outcomes.
This helps explain why MRI findings often overlap between verbal and nonverbal autistics.
Is there an MRI marker for nonverbal autism?
Or, to put this another way, if you look at a brain MRI of any nonverbal austic person and compare it to a brain MRI of any person with normal spoken language, will Broca’s area appear different in the autistic individual?
Could a neuroscientist look at a random brain MRI and say, “This person has nonverbal autism”?
Well, maybe in the Star Trek universe.
Despite extensive research, there is no MRI feature that reliably distinguishes nonverbal autism.
- Some nonverbal autistics do show atypical Broca’s area asymmetry or reduced connectivity.
- Others show brain patterns similar to verbal autistic individuals or even to neurotypical controls.
Because of this overlap, MRI can’t be used to reveal nonverbal autism or to explain speech differences on its own.
Broca’s area may look different on MRI in some nonverbal autistic individuals, particularly in terms of asymmetry or connectivity.
But those differences are neither universal nor specific.
There may still be a marker, though, yet to be discovered, that’s unique to only those with nonverbal ASD, but it looks as though that marker will be related to connectivity rather than something you can point to on the Broca area of the MRI image and say, “Oh, this here feature shows absence of speech.”
