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Neurobiology

Neurobiology of autism

An overview of what brain research has found about autism, from brain growth and networks to cells, senses, memory and reading, and how much of it is settled. Each section links to a full entry.

A short tour of what brain scientists have learned about autism, and how sure they are. Each part links to a longer page.

Last reviewed 12 October 2026 · one person's reading of the research · 22 sources

Brain growth Established

On average, young autistic children, mostly boys in these studies, have larger brains than non-autistic children of the same age, visible on brain scans by about age 2 to 2½.1,2 In one large study, the average difference came from a subgroup of autistic boys with large brains.3

Full entryBrain growth across the lifespan How the size and shape of the autistic brain change from infancy to later life, what is well established, and how much of it applies only to some autistic people.

On average, young autistic kids have bigger brains than other kids their age. This shows up by about age 2.1,2 In one big study, the difference came from a small group of boys with big brains.3

Full entryBrain growth across the lifespan How an autistic person's brain grows and changes, from being a baby to being old. Some of this is well known. A lot of it is true for only some autistic people.
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Established

Summarizes the most settled finding in Brain growth. Several MRI studies that followed the same children agree; the samples were mostly boys.

Established

Many studies agree. Most of them looked at boys.

Brain networks Emerging

The idea that autistic brains have weak long-distance and strong local connections has not held up in a simple form. The largest pooled analysis found both weaker and stronger connections.4 Small head movements during scanning lower long-distance and raise short-distance measures, the same shape the theory predicts.5,6

Full entryBrain networks How brain regions coordinate their activity in autistic people, how the idea of weak long-range and strong local wiring has fared in large studies, what is known about three large networks, and what the oxytocin receptor findings amount to.

An old idea said autistic brains have weak far-away links and strong nearby links. Big studies found both weaker and stronger links, in different places.4 Moving your head in a scanner can make the same pattern appear by mistake.5,6

Full entryBrain networks How parts of the brain work together in autistic people. An old idea about long and short links has not held up well. Some other findings are still small and unsure.
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Emerging

Summarizes Brain networks. The large studies draw largely on the same shared data, so they are not independent of each other.

Emerging

The big studies share much of the same data, so they are not fully separate checks.

Cells and synapses Emerging

In one post-mortem study of 10 autistic and 10 non-autistic brains, the number of dendritic spines fell less between childhood and adolescence in the autistic tissue.7 Its authors proposed that autistic brains prune fewer connections, but the steps linking pruning to autism have been shown only in mice.7 Drugs aimed at the mTOR pathway did not improve thinking or autistic traits in two trials in tuberous sclerosis,8,9 and two large trials of bumetanide were stopped early because it did no better than placebo.10

Full entryCells and synapses What brain tissue, brain chemistry and drug trials show about synapses, the mTOR pathway and the balance of excitation and inhibition in autism, and how much of it rests on mice.

Synapses are where nerve cells connect. In one small study, autistic brains lost fewer of these connections between childhood and the teenage years.7 Clearing away extra links is called pruning. The idea that autistic brains prune less has only been tested in mice.7 Some medicines aimed at this did not help in trials.8,9,10

Full entryCells and synapses What scientists know about the tiny parts of the brain where nerve cells connect, and about some drugs tested in autism. Much of it comes from mice, not people.
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Emerging

Summarizes Cells and synapses. The tissue studies are small, much of the mechanism work is in mice, and drug trials disagree.

Word
Pruning

The normal loss of surplus connections between nerve cells during childhood and adolescence.

Emerging

The studies of brain tissue are small, and a lot of the work is in mice.

Sensory processing and prediction Emerging

A meta-analysis of 55 questionnaire studies found large differences from non-autistic people in how autistic people respond to sound, touch, light and other senses.11 Theories that explain this through prediction have had mixed results when tested, and a meta-analysis called their support limited.12,13 In young autistic children followed for a year, strong reactions to sensations predicted later anxiety, which is not the same as causing it.14

Full entrySensory processing and prediction How common sensory differences are in autism, what the prediction, thalamus and arousal theories propose, how those theories have fared when tested, and what is known about the link between sensory differences and anxiety.

Many autistic people react differently to sound, touch and light.11 Some scientists think this is about how the brain makes guesses. Tests of that idea have given mixed results.12,13 Toddlers with strong reactions to sensations were more likely to feel anxious a year later.14

Full entrySensory processing and prediction Many autistic people sense the world differently. This page covers how common that is, what scientists think might be going on in the brain, and what tests of those ideas have found. It also covers how sensory differences and worry are linked.
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Emerging

Summarizes Sensory processing and prediction. Sensory differences are well documented; tests of the prediction theories are mixed, and the studies of what comes first are few.

Emerging

Sensory differences are well known. Ideas about why are still being tested.

Memory Established

Three meta-analyses find that autistic people score lower on average on tests of memory for events and lists.15,16,17 The gap is larger when people must recall without help than when they only have to recognize what they saw before.15

Full entryMemory What meta-analyses show about memory in autistic people, which kinds of remembering differ on average and which do not, how much depends on the way memory is tested, and how little is settled about the brain behind it.

On average, autistic people score a bit lower on tests of remembering events and lists.15,16,17 The gap is bigger when you must remember without help. It is smaller when you only have to spot what you saw before.15

Full entryMemory What scientists know about memory in autistic people. Some kinds of memory differ a little on average, and some do not. A lot depends on how memory is tested. Much less is known about the brain parts behind it.
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Established

Summarizes Memory. Three meta-analyses agree, though they draw on many of the same studies and mostly on male samples.

Established

Several big reviews agree. Most people studied were boys and men.

Hyperlexia and reading Emerging

Hyperlexia, reading words early and well, is found in a minority of autistic children, with figures between about 9% and 19% depending on how it is defined.18,19,20 As a group, autistic children tend to read words at about the expected level and understand what they read less well.21,22

Full entryHyperlexia and reading Some autistic children read words early and well, often before they understand what they read. How hyperlexia is defined, how common it is, what brain imaging has and has not shown, and how it relates to dyslexia and to reading in autism generally.

Some autistic kids read words early and very well. This is called hyperlexia. Studies put it at about 1 in 10 to 1 in 5 autistic kids.18,19,20 As a group, autistic kids often read words fine but find it harder to understand what they read.21,22

Full entryHyperlexia and reading Some autistic kids learn to read words very early, often before they understand what they read. This is called hyperlexia. Here is what scientists know about it, and what they are still not sure about.
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Emerging

Summarizes Hyperlexia. How common hyperlexia is comes from three single studies with different definitions.

Emerging

Each number comes from a different study. Each study measured it in its own way.

Sources

  1. 1Hazlett HC, Poe MD, Gerig G, et al. Early brain overgrowth in autism associated with an increase in cortical surface area before age 2 years. Archives of General Psychiatry 2011. https://doi.org/10.1001/archgenpsychiatry.2011.39 ; https://pubmed.ncbi.nlm.nih.gov/21536976/
  2. 2Schumann CM, Bloss CS, Barnes CC, et al. Longitudinal magnetic resonance imaging study of cortical development through early childhood in autism. Journal of Neuroscience 2010. https://doi.org/10.1523/JNEUROSCI.5714-09.2010 ; https://pubmed.ncbi.nlm.nih.gov/20335478/
  3. 3Lee JK, Andrews DS, Ozonoff S, et al. Longitudinal evaluation of cerebral growth across childhood in boys and girls with autism spectrum disorder. Biological Psychiatry 2021;90:286–294. https://doi.org/10.1016/j.biopsych.2020.10.014 ; https://pubmed.ncbi.nlm.nih.gov/33388135/
  4. 4Di Martino A, Yan CG, Li Q, et al. The autism brain imaging data exchange: towards a large-scale evaluation of the intrinsic brain architecture in autism. Molecular Psychiatry, 2014. https://doi.org/10.1038/mp.2013.78
  5. 5Power JD, Barnes KA, Snyder AZ, et al. Spurious but systematic correlations in functional connectivity MRI networks arise from subject motion. NeuroImage, 2012. https://doi.org/10.1016/j.neuroimage.2011.10.018
  6. 6Van Dijk KRA, Sabuncu MR, Buckner RL. The influence of head motion on intrinsic functional connectivity MRI. NeuroImage, 2012. https://doi.org/10.1016/j.neuroimage.2011.07.044
  7. 7Tang G, Gudsnuk K, Kuo SH, et al. Loss of mTOR-dependent macroautophagy causes autistic-like synaptic pruning deficits. Neuron, 2014. https://doi.org/10.1016/j.neuron.2014.07.040
  8. 8Krueger DA, Sadhwani A, Byars AW, et al. Everolimus for treatment of tuberous sclerosis complex-associated neuropsychiatric disorders. Annals of Clinical and Translational Neurology, 2017. https://doi.org/10.1002/acn3.494
  9. 9Overwater IE, Rietman AB, Mous SE, et al. A randomized controlled trial with everolimus for IQ and autism in tuberous sclerosis complex. Neurology, 2019. https://doi.org/10.1212/WNL.0000000000007749
  10. 10Fuentes J, Parellada M, Georgoula C, et al. Bumetanide oral solution for the treatment of children and adolescents with autism spectrum disorder: results from two randomized phase III studies. Autism Research, 2023. https://doi.org/10.1002/aur.3005
  11. 11Ben-Sasson A, Gal E, Fluss R, et al. Update of a Meta-analysis of Sensory Symptoms in ASD: A New Decade of Research. Journal of Autism and Developmental Disorders, 2019. https://doi.org/10.1007/s10803-019-04180-0 ; https://pubmed.ncbi.nlm.nih.gov/31501953/
  12. 12Angeletos Chrysaitis N, Seriès P. 10 years of Bayesian theories of autism: A comprehensive review. Neuroscience & Biobehavioral Reviews, 2023. https://doi.org/10.1016/j.neubiorev.2022.105022 ; https://pubmed.ncbi.nlm.nih.gov/36581168/
  13. 13Cui K, Lin X, Gao R, et al. A Systematic Review and Meta-analysis of Empirical Evidence for the Simple Bayesian Model of Autism. Neuropsychology Review, 2026. https://doi.org/10.1007/s11065-025-09672-8 ; https://pubmed.ncbi.nlm.nih.gov/40576893/
  14. 14Green SA, Ben-Sasson A, Soto TW, et al. Anxiety and Sensory Over-Responsivity in Toddlers with Autism Spectrum Disorders: Bidirectional Effects Across Time. Journal of Autism and Developmental Disorders, 2012. https://doi.org/10.1007/s10803-011-1361-3 ; https://pubmed.ncbi.nlm.nih.gov/21935727/
  15. 15Griffin JW, Bauer R, Gavett BE. The Episodic Memory Profile in Autism Spectrum Disorder: A Bayesian Meta-Analysis. Neuropsychology Review, 2022. https://doi.org/10.1007/s11065-021-09493-5 ; https://pubmed.ncbi.nlm.nih.gov/33954915/
  16. 16Geng K, Wang Y, Fu W, et al. Episodic memory impairment and its influencing factors in individuals with autism spectrum disorder: systematic review and meta-analysis. European Archives of Psychiatry and Clinical Neuroscience, 2025. https://doi.org/10.1007/s00406-024-01889-7 ; https://pubmed.ncbi.nlm.nih.gov/39269621/
  17. 17Desaunay P, Briant AR, Bowler DM, et al. Memory in autism spectrum disorder: A meta-analysis of experimental studies. Psychological Bulletin, 2020. https://doi.org/10.1037/bul0000225 ; https://pubmed.ncbi.nlm.nih.gov/32191044/
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  21. 21Vale AP, Fernandes C, Cardoso S. Word reading skills in autism spectrum disorder: A systematic review. Frontiers in Psychology, 2022. https://doi.org/10.3389/fpsyg.2022.930275
  22. 22Brown HM, Oram-Cardy J, Johnson A. A Meta-Analysis of the Reading Comprehension Skills of Individuals on the Autism Spectrum. Journal of Autism and Developmental Disorders, 2013. https://doi.org/10.1007/s10803-012-1638-1