Autism: The Brain Science
Brain differences in Autism by Dr Victoria Lawson (2026)- date for citation purposes.
I am delighted for the information to be shared but ask that people using for their professional purposes cite the source of their information.
It is widely accepted that autism is a neurological and developmental condition that usually appears in the first few years of life. Although, as we know from the wide spectrum of genetic contributions that form an autistic person’s DNA, no two autistic people are alike. This brings up one of my favourite phrases regarding autism: “if you have met one person with autism, then you have met one person with autism” coined by Dr Stephen Shore.
Despite the variation or ‘heterogeneity’ of people with autism, it is also widely agreed that the structure of the brain of a person with autism is different to a neurotypical person’s brain. Research has been undertaken into brain differences in autism since the 1960’s and often has its roots in studies on other mammals, such as mice and monkeys. As technology has progressed researchers have refined their approaches to use EEGs, PET scans, and functional imaging (fMRI’s) and have moved confidently to studying people.
Here is a collection of some of the most up to date research on specific areas of the brain and their likely impact on the symptoms of autism. Research progresses and evolves all the time, so I invite you to take this as a guide only and not an absolute answer to structural brain differences causing autistic experiences.
Included is research where there is a general professional consensus on findings, including metanalysis and systematic reviews. Left out are more disputed theories, such as the role of the amygdala, due to disparity in findings over time over its potential role in autism.
This isn’t to say the more disputed theories aren’t correct, it’s more that the brain does not come with a road map or guidebook or pointy figure saying, “this bit does this”. These areas are a guide, and the complexity of the brain cannot be understood only in its component parts. Many researchers, like Shuo Wang in 2023 in the paper “a revisit of the amygdala theory of autism, twenty years after”, call for a wider view on the functioning of the brain and autism, considering global brain connectivity rather than focusing on the impact of just one structure.
The science evolves and grows and builds on each other’s foundational theories.
This information aims to foster an awareness that regardless of the detail, there is a clinically established difference in the brain structure and function of individuals with autism.
Apologies if this feels a bit theory heavy, I’ve tried to keep it whistlestop and feel strongly that an awareness that a brain difference is at the root of many of the challenging experiences you and /or your young person has. My experiences tells me that understanding the likely cause can take the heat out of some high voltage autism parenting moments. I’ve tried to summarise what this means for what we see in behaviours in bold so please feel free to skim and focus on the bold bits.
So here we go:
Reduced volume of the corpus callosum:
The brain is formed of two hemispheres which work together and are linked by the corpus callosum. The corpus callosum is essentially the bridge between the two hemispheres of the brain and supports our everyday functioning and understanding. The volume of the bridge implies how well the two sides of our brain can communicate with one another.
In 2021 Prigge and colleagues completed a longitudinal study of 105 males with autism and 125 controls. They found that as children these males with autism had a larger brain volume, as measured using MRI scanning than the control group that did not level out until late childhood. They found that individuals with autism showed ventricle volume differences and a reduced corpus callosum (CC) volume by adulthood.
Reduced corpus callosum volume is an interesting finding and is reported to have been replicated across studies.
Corpus callosum is implicated in interhemispheric communication and atypical development has implications for behavioural functioning. The researchers found a correlation between ADOS scores and the discovered atypical corpus callosum structure. They reported smaller corpus callosum volume was correlated to higher or persistent ADOS scores, indicating the continued presence and/or severity of autism symptoms.
Goldstein and colleagues in 2023 elaborated on the potential role of the corpus callosum in the national library of medicine. They provided an account of how the corpus callosum connects the two hemispheres of the brain and the implications this has on human functioning. They highlighted the role of the corpus callosum in helping us process and integrate information. This information can be sensory, motor and cognitive in nature and can have implications on cognitive and motor functioning. According to the handbook of clinical neurology (2019) the corpus callosum has been implicated in integration between both hemispheres and subsequently the ability to perceive, comprehend and act fully upon sensory input.
Reduced corpus callosum volume was found by Scaccabarozzi and colleagues in July 2025 in 35 children studied with autism. They reported correlations between reduced corpus callosum volume and repetitive behaviours and some challenges in motor skills seen in children with autism.
Atypical activation and connectivity of the Insula
Summarising literature and highlighting functional MRI studies on the area, Nomi and colleagues in 2019 highlighted the differences in the insula in individuals with autism. The insula has long been an area of interest for researchers due to its implications across individuals and diagnoses. The insula forms part of the limbic system and is involved in threat detection, emotional regulation and interoception (the sense of perceiving and understanding what is happening within our body). The insula is also said to be involved with speech and language tasks. The insula in the brains of individuals with autism is said to have weaker connections with other brain structures and does not form the “salience network” coined by Uddin and Menon in 2010 in the same way a neurotypical brain does. This network is said to support the integration of external sensory input with our internal states. (The link between the messages we receive from outside to how they are experienced in our body)
The anterior insular is said to play a role in social perception and emotional recognition and be part of the mirror neuron system supporting with perceiving, imitating and empathising with the expressed emotions of another individual. As the insular is documented to play such a pivotal role in numerous social, emotional and sensory integratory processes, it is believed that atypical insular function may underly a range of symptoms of autism.
The thalamus and the cortex
It is largely agreed in neuroscience that the prefrontal cortex is responsible for the higher order functioning in our brains. It is said to play a key role in integrating and modulating numerous brain functions in response to what is perceived by the senses. The prefrontal cortex includes the basal ganglia, the thalamus and the cerebellum. Using functional neuroimaging of 81 individuals with autism and sex matched typically developing control individuals, Ayub and colleagues in 2021 found evidence for thalamocortical hyperconnectivity in individuals with autism. This means there is an increased connectivity between the thalamus and the cortex and this has implications for the sensorimotor processing differences in autism and symptom severity.
Further research has been made into the difference in connections between structures in the brains of people with autism and some of this has spanned over the past decade. Although not replicated in all studies, a recent addition to the research by Weber and colleagues in 2024 has built on previous research indicating there may be a reduction in longer connections between brain structures. Using specialist equipment to measure brain function in very young children in 2014, Kikucki and colleagues completed a study on 50 children with autism and 50 matched typically developing controls. Their results suggested a reduced connection between frontal lobes and posterior brain areas, strengthening the theory that connectivity between the frontal cortex and other systems is poorly synchronised and less responsive in autism. The posterior brain areas with poor connection include the occipital lobe related to vision, the parietal lobe, related to special awareness and sensory processing and the temporal lobe, related to working memory. Atypical brain connectivity is believed to play a major role in the experience of autistic symptoms.
Fewer synapses in the autistic brain:
There is emerging evidence that the brains of individuals with autism have fewer synapses than neurotypical counterparts:
In 2024 McPartland and colleagues at Yale completed a small scale study on live brains using PET Scanning. The study of live brains in itself is a technological leap in research and hopefully more of its kind are to be looked forward to. They compared 12 autistic adults (confirmed by administration of the ADOS) and 20 neurotypical adults. They found the autistic adults consistently had fewer synapses in their brains.
We understand that synapses are the way that neurons communicate within the brain, allowing the brain to process information and control bodily functions. As our brains are neuroplastic and therefore constantly developing it cannot be known from this study exactly how (or if) the brains of autistic individuals are different at birth, and how much is through changes in development and experiences (synapse elimination or formation through development).
What we do know is that fewer connections can mean slower cognitive functioning, so could account for executive functioning difficulties with people with autism.
So there is a collection of research in regards to the difference in brain structures in individuals with autism. As previously mentioned, it is by no means definitive or exhaustive and certainly not perfect. As autism is a spectrum condition and as such ‘heterogenous’, therefore no group is the same and this can made research complicated and limited.
Much research is also undertaken on male brains and researchers acknowledge the need to include more gender diversity in participants.
