Autism, or Autism Spectrum Disorder (ASD), is a neurodevelopmental condition that affects how people communicate, socialise, and process the world around them. While autism has been recognised for over a century, our understanding of its neurological roots has grown dramatically in recent decades. From changes at the level of brain cells to insights from psychology and cognitive science, neuroscience is beginning to reveal how autistic brains work differently — not incorrectly, just differently.
The History of the Term Autism
The word autism comes from the Greek autos, meaning “self.” It was first used in 1911 by Swiss psychiatrist Eugen Bleuler to describe patients who seemed deeply withdrawn into their own world. However, the modern concept of autism began with two researchers working independently in the 1940s: Leo Kanner in the United States and Hans Asperger in Austria.
Kanner described children who showed difficulties with social interaction and communication, as well as repetitive behaviours. Asperger described a group of boys with similar traits but often with strong language and intellectual skills. For decades, these two descriptions were seen as separate conditions: “Kanner’s autism” and “Asperger’s syndrome.”
The classification of autism has evolved with each edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM) — the key guide used by clinicians worldwide:
DSM-III (1980): Autism was officially recognised as “Infantile Autism,” distinguishing it from childhood schizophrenia.
DSM-IV (1994): Introduced the broader term Autism Spectrum Disorders, including Asperger’s syndrome and Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS).
DSM-5 (2013): Merged these categories under one diagnosis: Autism Spectrum Disorder. This change reflected the idea that autism is not a single condition, but a spectrum that varies in severity and traits.
This shift helped researchers and clinicians view autism as a complex interplay of neurological, genetic, and environmental factors — not as a single “disease” but a difference in brain development.
How Synapses May Be Affected
At the most basic level, the brain is a network of around 86 billion neurons. These neurons communicate through synapses, tiny junctions where chemical messengers called neurotransmitters carry signals from one neuron to another.
Research suggests that autism may involve differences in how these synapses form, function, and are pruned during development. Normally, the brain goes through periods of synaptic pruning — removing weaker connections and strengthening important ones. In autistic individuals, studies have shown that this pruning may be less efficient, leading to an unusually high number of synaptic connections.
This could help explain why some autistic people experience sensory overload or heightened perception. Their brains may literally be processing too much information at once.
Excitation and Inhibition Balance
Another key finding relates to the balance between excitatory and inhibitory signals in the brain. Excitatory signals (mostly driven by the neurotransmitter glutamate) stimulate neurons, while inhibitory signals (often via GABA) calm them down. If this balance shifts — say, too much excitation or not enough inhibition — the brain’s circuits can become overactive or poorly synchronised.
Researchers have found evidence of this imbalance in regions linked to social cognition, communication, and sensory processing, such as the prefrontal cortex and temporal lobes. These changes don’t mean “damage” to the brain, but rather a different tuning of neural activity that affects how information is filtered and prioritised.
Genetic and Molecular Clues
Many genes linked to autism affect synaptic proteins — molecules that help neurons form and stabilise connections. For instance, mutations in genes like SHANK3, NRXN1, and NLGN3 can disrupt how synapses develop or communicate. These findings point towards autism as a synaptopathy — a condition involving differences at the level of synaptic structure and signalling.
The Psychology and Theory of Mind
Autism has also been studied through psychology and cognitive neuroscience. One of the most influential ideas is the Theory of Mind (ToM) hypothesis — the ability to understand that other people have thoughts, feelings, and perspectives different from one’s own.
In classic experiments, such as the Sally-Anne test, children are shown two dolls: Sally puts a marble in a basket and leaves the room, while Anne moves it to a box. Neurotypical children usually understand that Sally will believe the marble is still in the basket. Many autistic children, however, answer based on what they know — the marble’s actual location. This suggests differences in spontaneous social reasoning rather than lack of empathy.
Beyond Theory of Mind
Later research showed that Theory of Mind is only one part of the picture. Other cognitive theories have added depth:
Weak Central Coherence: Autistic individuals often focus on details rather than the “big picture.” This can lead to exceptional pattern recognition and attention to fine detail.
Executive Function Differences: Some find it harder to switch tasks or plan sequences of actions, which might explain repetitive behaviours.
Enhanced Perceptual Functioning: Many autistic people show heightened perception in sound, colour, or touch — aligning with neuroscientific findings of altered sensory processing.
Bridging Psychology and Neuroscience
Brain imaging studies have linked these cognitive traits to differences in neural connectivity. For example, areas involved in social understanding (like the medial prefrontal cortex and temporal-parietal junction) may show reduced synchronisation during social tasks. Meanwhile, sensory regions can be more active or more connected. This blend of hyper- and hypoconnectivity mirrors the diversity seen across the autism spectrum.
Conclusion
Autism is not a single condition, but a mosaic of brain differences affecting how people perceive and interact with the world. From the history of its definition to the discovery of altered synaptic signalling and distinct patterns of cognition, neuroscience has helped shift our view of autism from disorder to difference.
Understanding these mechanisms doesn’t just deepen our science — it encourages society to embrace neurodiversity and support individuals in ways that align with how their brains work best. If you’d like to learn more about these amazing roles of water in the brain, check out my video on the topic.
Thanks for reading and please comment on YouTube with any questions! Click here to see the other blogs and associated videos I have about neuroscience! 🙂
If you want to support this evidence based neuro-explainer content then feel free to buy me a coffee or become a patreon! 😊
