The Neuroscience of Autism ft. 12tone
When researchers talk about the “normal” human brain, there really isn’t any such thing. But trying to understand how brains vary is valuable, because it helps us understand how differences in the structure and function of the brain lead to differences in behavior. Hey there, Brainiacs! I’m Alie Astrocyte. This week, I want to talk about one particular type of variation in the human brain: Autism. Our friend Cory is here to share his personal experiences with us! Hey Cory, thanks for being here! Hey Alie! Cory is the creator and host of 12Tone, a channel where he breaks down your favorite songs and explains the core concepts of music theory. Cory is also autistic, so he has personal experience with this topic! Yep! I was diagnosed as a child, although no one actually told me until I was 15. It's taken me a long time to figure out what it means, and I think I'm still in that process, but just knowing the term has been really helpful. It's a good way to remind myself that I'm not broken, and that there are other people out there dealing with the same stuff.
I want to start by saying something important here: while the scientific and medical literature calls autism a disorder, that does not make it a disability. When we talk about autism, we often talk about deficits, but that should not limit us from seeing the person as a whole. The only people who really get to decide what autism is are the people who have it. It can be difficult to explain what the experience of autism is like, because I've never gotten the chance to try living without it. It's a part of who I am, and it affects pretty much every aspect of my life, but given how complex personalities are, it's basically impossible to tell which things are the result of my autism and which things are just..
Me. In fact, I don't really think there's a point in differentiating between the two. I think it's easy to assume that all autistic people are basically the same, but each of us has a different experience with the condition and with life in general. After all, we're still people. Exactly! Autism is a really complicated condition - it’s defined by a set of behaviors, and it exists on a spectrum, meaning that it affects individual people differently, and to varying degrees. It’s actually now called autism spectrum disorder, or ASD, to encompass the broad span of symptoms and severity.
And it affects a /lot/ of people - in 2016, the CDC released a report that nearly 1 in 70 kids in the US is autistic. There’s no single underlying genetic or environmental cause for ASD, so there’s no easy blood test to figure out if you have it or not. Instead, doctors screen for certain developmental delays and behavioral patterns beginning at about 18 months of age. Symptoms of autism include language delays, difficulty with eye contact and non-verbal communication, sensory avoidance or, conversely, sensory seeking, and stereotyped behaviors, including obsessive special interests, repetitive actions, and stimming, short for self-stimulation, which involves intentionally creating specific sensory inputs in order to calm down, like rubbing your hands on certain textures or making soothing noises. But what causes these symptoms in the first place? First off, let’s just get this out there: vaccines do not cause autism. There is no link between rate of vaccination and likelihood of an autism diagnosis. And like I said before, there’s no single underlying cause of autism - it really seems to be a combination of environmental factors and genetics. Some genetic mutations and disorders - like Fragile X Syndrome - are associated with high rates of ASD.
And having a parent or sibling with ASD makes it far more likely that someone will have ASD themselves. Over a hundred genes have been linked to the condition, but none of them seem to cause it. What’s more likely is that certain environmental factors - like if a mom has a fever while she’s pregnant - combined with genetic traits, come together in a perfect storm, resulting in ASD. So what makes our brains different? Even though a diagnosis is based on behavioral screening, scientists are learning that there are some key differences between the brain of someone with ASD and someone without. Right! When looking at overall brain size, autistic kids - between 2 and 4 years old - have, on average, a bigger brain than their non-ASD counterparts. That difference isn’t seen in older kids, though, which scientists think means there’s a difference in the rate of brain growth in early childhood. Researchers have also found that autistic kids have more grey matter than usual, without showing a similar growth in white matter.
Grey matter - which got its name because...well, it kinda looks grey - is full of neuronal cell bodies, dendrites, synapses, and glial cells. It’s sort of where the magic of synaptic signalling happens - it’s critical for all kinds of things like muscle control, sensory perception, memory, emotion, and even decision making. White matter, on the other hand, looks white because it mostly consists of myelinated axons. Myelin, which is the insulation around axons that helps them send signals faster, looks kinda white. White matter is like a bunch of XLR cables hooked up to a mixing board. It speeds up the signals, adjusts them as needed, and coordinates communication between brain regions. So what this could mean is that not only could ASD be related to differences in brain development - it could also be related to differences in communication within the brain. People with ASD may have more connectivity in the grey matter, and less white matter connecting across brain regions - manifesting in some of the typical behaviors associated with the condition.
Certain brain regions seem to be affected by ASD, too - one of the theories about why autistic people sometimes struggle with social interaction is that their mirror neuron system develops a bit differently. These neurons are unique because they fire when a person performs an action, or when they watch another person perform an action. So just watching my facial expressions or watching Cory draw makes your mirror neurons fire. Cool, right? In kids with ASD, this circuit seems to have a delayed response, which could indicate less signaling.
Changes have also been seen on the microscale - for example, a bunch of research has found changes in the development of synapses in ASD, which could lead to changes in how neurons are communicating with one another, and result in neurons not connecting properly. This could also help explain why autism is frequently associated with epilepsy. Children with autism also tend to have markers of inflammation in their brains - they have increased levels of inflammatory proteins called cytokines, and their microglia - the brain’s immune cells - are super active.
Because the immune system is a critical part of brain development, this shift could be affecting how the brain is growing during childhood. Studies using fMRI to examine the dynamic relationships between different brain regions have reported contrasting results - some say that in ASD, the brain has hyperconnectivity - it’s more connected than usual, while others say the opposite. Most of this work has been done in children - usually with the goal of helping identify and diagnose ASD sooner, so kids can start getting the resources they need, if any, to help them as they grow up. But ASD still isn’t very well understood, on the macro or the microscale - in fact, labs like mine are hard at work trying to better understand how all kinds of brain cells may be involved in all of these brain differences. All of the studies we’ve described today are really just talking about averages; just like neurotypical brains have a lot of variation, so do autistic ones! Not every brain with ASD will show obvious changes in brain size or connectivity. Just like the symptoms, brain differences exist on a spectrum. There's definitely still plenty of research to be done, but right now I think the most valuable thing we can do is just talk about it.
The internet has made it a whole lot easier for autistic people to come together to tell our stories and to advocate for ourselves and for each other. And that's important because, without naming names, many major autism advocacy groups have almost no autistic people in positions of real power, and the pictures they wind up painting of us look nothing like our actual lives. That said, a lot of scientists have worked towards better understanding the brain differences between autistic and neurotypical people.
With that knowledge, we can figure out how to best work with autistic kids, and develop treatments and therapies to help them navigate their lives and the world. There’s a lot of room to grow and understand autism - and we are lucky to have people like Cory who are willing to be so open and honest with us. Cory, thank you so much for joining us today for this video, and for sharing your experiences with us. Of course, thanks for having me! Cory is a musical genius and he shares his passion for music theory over at 12Tone. He’s an amazing YouTuber and (short clips play of songs)...recognize any of those, brainiacs? Then you should check out our other collaboration we did with him at his channel about how our brains can recognize that one 90s song, even after hearing it for less than half a second! Thanks for watching this episode of Neuro Transmissions.
If you liked it, hit that thumbs up button, and subscribe so you can catch our next fun collaboration with one of our YouTube friends! Head on over to our Patreon page to see Cory's drawings for this episode. Until our next transmission, I’m Alie Astrocyte - over and out.
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