The Other Autism

EP31: Neural Pruning, Synesthesia, and Autism

January 22, 2024 Kristen Hovet Episode 31
The Other Autism
EP31: Neural Pruning, Synesthesia, and Autism
Show Notes Transcript Chapter Markers

What aspects of the brain differ between autistic people and non-autistic people? Do these brain differences lead to things like synesthesia in autistic people? Synesthesia is when your senses or perceptions overlap, like when you think of a number and see waves of red or some other colour. Or when you can feel in your own body the sensations and physical pain of another, just by looking at them!

In this episode, I also talk about ableist perspectives in autism research, secondary autism, neurons, glial cells, early brain development, mirror-touch synesthesia as the basis of deep empathy, and much more!

Watch this episode on YouTube.

If you'd like to know more about topics discussed in this episode, check out:

"What Is Synaptic Pruning?" by Jacquelyn Cafasso

"Astroglia in Autism Spectrum Disorder" by Kinga Gzielo and Agnieszka Nikiforuk

"Regional Differences in Synaptogenesis in Human Cerebral Cortex" by Peter Huttenlocher and Arun Dabholkar

"Microglia in the Pathogenesis of Autism Spectrum Disorders" by Ryuta Koyama and Yuji Ikegaya

"Astrocytes and Microglia and Their Potential Link With Autism Spectrum Disorders" by Francesco Petrelli et al.

"Balancing Excitation and Inhibition in the Autistic Brain" by Charlotte Pretzsch and Dorothea Floris

"Synaptic Growth, Synesthesia and Savant Abilities" by Martin Silvertant

"Neuroinflammation, Mast Cells, and Glia: Dangerous Liaisons" by Stephen D. Skaper et al.

"Lack of Neuron 'Pruning' May Be Behind Many Brain-Related Conditions" by Clare Wilson

"Microglia and Astrocytes Underlie Neuroinflammation and Synaptic Susceptibility in Autism Spectrum Disorder" by Yue Xiong et al.

Episode outro music: "It's Too Much" by Kristen Hovet 

Theme music: "Everything Feels New" by Evgeny Bardyuzha.

All episodes written and produced by Kristen Hovet.

To submit a question to possibly be answered in a future episode, please email kristen.hovet@gmail.com

Become a patron on Patreon!

Buy me a coffee!

Kristen Hovet:

Hey everyone, my name is Kristen Hovet. Welcome back to The Other Autism podcast. Today we're talking about neural pruning and how it differs in the brains of autistics versus the brains of neurotypicals. I'll also discuss synesthesia. I don't know if I'm saying that right. I'm saying it. I think I tried getting Google Translate to help me and I'm still not saying it right. So, actually, speaking of Google Translate, I think she's going to help me in this episode, so I'm going to need her here. One sec, okay, synesthesia. Synesthesia, yeah, where one sensory or cognitive pathway activates a second or maybe even third sensory or cognitive pathway. But before we get into all of that, I wanted to say sorry for the long gap of time between this episode today and the last one in November. So a lot has happened between November and today, which is January 21st. I did have an interview lined up for December and we had to cancel it last minute and then holiday rush began, so I didn't have time to set up something else. And there's other reasons too. I probably could have fit something in there if I was at my usual healthy, energized kind of self. So I finished my Master of Health Studies degree with a major in health research in December, then went away for a while for the holidays, then I got sick a few times and now I'm back. So my degree, as some of you know, took three years to complete. I was considered a full time Master's student and I was also working for most of that working full time at the same time. It would have taken me four years in the program I was in, but I did have some Master's level classes under my belt from before I had cancer, before I was diagnosed with cancer, when I was still pursuing a Master's in counseling psychology. I got to use those classes towards my degree, thankfully. Anyway, the last three years have been a lot. It's been a lot of really good things and a lot of very challenging things. Also, so while I was in school and working, I went through the end of an almost 12 year long relationship that upended everything, including, I mean, that has an impact on your self- concept. It has an impact on how you spend your time and it leads to a sort of having to like readjust everything, your schedule, how you spend your free time. It impacts everything. So I went through the end of that and, about a year and a half after that, the beginning of an amazing new relationship. I also worked through grief related to the loss of my brother and the loss of a friend. Not to mention, I moved twice in the past two years alone. And then, when I moved to my current place here, I got evacuated from fires this past summer, so that was literally like a couple months after I moved. It's like, now you have to run away from fire and you have to stay out of your house for a week, and I was lucky that I had a place to stay, because not everyone was so fortunate and some people lost their homes. That was terrifying and I sort of just kept trucking along. I got back home and just kind of almost tried to forget that that all had happened, because it was just like, really like, really, you're gonna, this is gonna be what's happening right now. So anyway, on top of all of that, there was significant work related stress that I've been dealing with off and on, I would say, for a long time, and I enjoy my work, but there are some stressful elements. And I think all of it just finally caught up with me. I have a lot of things in place to sort of like deal with impacts of stress and deal with impacts of challenging life events happening, but it's like all of those, those resources and things I have in place were not enough, I don't think, and it all just kind of caught up and I was just blindsided by the after effects, all of a sudden. I found myself pretty burnt out, despite, like I said, so many good things going on and so many elements that bring resilience to my life, like, I think internal elements and also support system outside of myself. I also have, like I stick to a pretty clear routine, a pretty strict sleep schedule, all these things that I know to help myself. It was just not enough and what happened was like I've experienced burnout before, which I did talk about, ironically, last couple episodes ago. I was talking about burnout. If you heard that one, you know that I've experienced burnout before, and this one was like it came up very, very slowly and then it just knocked me off my feet. What happened was I was able to every day, get through the workday, do my work, concentrate on work, and after that, when I would normally do some errands and then work on a podcast or do something like that, I couldn't do anything else for the rest of the day other than washing dishes and vacuuming and then playing with my cat and then watching TV. Like I really, I had zero energy for anything more, unfortunately, and there were so many things I wanted to do with the podcast and so many emails I wanted to respond to and I just. I appreciate that several of you took the time to check in and I fairly confidently can say I'm back. I don't know if I'm going to be able to keep up the two or three episodes a month. We'll see. Ideally, as I've said before, I would love to have The Other Autism be my full-time job. That is my dream. Unfortunately, I'm not quite close there yet. I don't know if a lot of you know, but to be part of the bigger advertising groups or to get in on the bigger advertising that podcasts do, you have to have 10,000 listens per episode, to even sign up for a lot of those. Actually, most of them have some very strict guidelines like that and I'm not quite there yet for that many per episode. But that's my goal to get there and to be able to give you more content, more interviews, and do a lot of other things. It's my goal, my dream, to be able to do that. I felt like this was a significant stumbling block this past couple months and I really don't want it to happen again. I can't promise that it won't, but I don't foresee all the things that happened in the last few years happening ever again to me. Knock on wood. But I don't foresee all of those things happening again or happening in such quick succession, one after the other, the way that they have. I could have chosen an easier subject for myself, in the face of burnout especially, but once I started reading about it, I knew I had to do this episode and I knew it had to be the first one of 2024. The topics I'm going to cover today are, as I said, not easy. For that reason, I'm going to try to take it slow and break things down without getting too deeply into the weeds or the unnecessary details. I think it's important, too, since the research is still underway in this area, to keep things a bit high level, and what I mean by high level here is that I'll try to stick to more general summaries as opposed to getting into the minute biological, neurological details. I also wanted to mention that I was a bit disturbed while I was reading the research on these neurological, brain-based aspects of autism. I found that the language used in a lot, not all, but a lot of the content was quite in line with the deficit model of autism and a lot of it seemed focused on like oh, if we understand these neurological differences in autistic brains, then one day we might be able to fix them. I just want to say that's so against what I stand for. It's so against what almost everyone active in the neurodiversity space stands for. I don't support the search for treatments or cures for autism. I don't support researchers or research that claim in any way to have autism eradication as their goal. But at the same time I need to report on the research and I find myself often having to make do with what's there. I think that's the case for a lot of areas, not just autism research. The research on these particular topics is quite different from other autism research I've been reading lately, which has been quite a bit more neurodiversity affirming and where the writers and researchers worked hard to challenge ableism with everything they did, starting from the actual research and the research questions and even the composition of the research team, to the writing of their research publications and conveying of their study results. So a lot of that research, not the research I read for this episode, but the other research I'm talking about, I did notice that a lot of their research teams had autistic academics and researchers or autistic clients that were part of the research team. I will say it was disheartening to kind of feel like, with a lot of the research I read for this episode in particular, I was going back in time or reading regressive stances from those who clearly hadn't worked to ensure they're following current best practice when it comes to writing about and researching autism and autistic people. It's unfortunate that they don't seem to realize just how many people they're alienating with their word choice and the perspectives they're taking or allowing themselves to uncritically fall into. I guess the equivalent might be a study where they're researching differences in the brains of gay or queer people versus the brains of straight or non queer people and in addition to objectively studying these differences, they oddly also take a stance that being queer is not ideal or even that there could one day be a cure or brain based fix for being gay. Now, that sounds obviously horrible and absurd, right? Well, it's also horrible and absurd for it to be 2024 and researchers and other experts still talking this way about autism and being autistic, like assuming we all want to be cured or assuming that we want interventions that get rid of our sorry, getting worked up here and trying to destroy my equipment. Some people have challenged me behind the scenes when I talk this way, when I talk about this stuff. They say well, you're dismissing the autistic people who suffer greatly because of their autism and who might want some kind of intervention to take autistic symptoms or traits away. While I think my stance and response is still evolving, especially in the way I articulate it, I will say that I think that autistic people who want a cure or intervention that theoretically could take their traits away or greatly reduce them have likely internalized a very negative, deficit based view of autism. I mean, it makes sense if you grow up being told in both direct and indirect ways constantly that autistic traits are inferior or undesirable and you've never challenged these perspectives for yourself or been able to, heck yes, you're going to hold these same perspectives. Secondly, they likely have co-occurring conditions, such as intellectual disability or physical disabilities that are impacting them the most. These folks typically have what's called a syndromic form of autism, where the autism is secondary to a wider syndrome, such as fragile X syndrome. Some even question if it's accurate to call these folks autistic, because it's like the autism very much, it's considered like secondary autism. The autistic traits are not the main factor, are not the main focus of the disorder. So it might not even be accurate to call those folks autistic. Someone with Rett syndrome or fragile X, are they autistic? The jury, I think, is still out and I think more people are raising the question like are they? I don't know if they're autistic, should we be calling them? Should we be lumping them in with the autistic community? Because, as it stands, syndromic forms of autism account for less than a quarter of the autistic population. Non-syndromic autism, it's much, much more common, accounting for over 75% of the autistic population. I think I've read higher, like 80-85%. To say it in another way, if you were to talk about cures for the syndromic forms of autism, it would be targeting the underlying factors leading to their broader medical condition, such as the genetic variants or mutations behind Rett syndrome, R-E-T-T syndrome. Autism or autistic traits that come with these syndromes are, as I said before, considered secondary. So why, I ask, are these syndromic forms of autism very often treated as the predominant experience of autistic people. I don't discount their experiences or that their medical challenges are more severe, generally speaking, when compared to non-syndromic autism. But I want to make it clear as well that we're talking about very different conditions and very vastly different experiences. I can say with confidence that the majority of autistic people do not want you to even come near them with any talk of cures or autism interventions or anything of the sort. So please think twice before assuming this is what we want or assuming you know what's best for us. We have the ability and the agency to speak for ourselves. Shocking right? No! Will all autistic people agree with the stance I've just conveyed here? Absolutely not. I'm level one autistic with the non-syndromic diagnosis of autism and I'm one person. So I definitely don't speak for others on the spectrum and I don't claim to even try to speak for anyone else. There's going to be similarities, of course, like there is with any human group, but I don't claim to be a voice for the entire autistic population, not even close. Some people in our community might have zero problems with deficit-based language and deficit framing of autism. Even my own language maintains some of the deficit sort of framing or talk, for example, when I use the word diagnosis or when I say things like when I got diagnosed as autistic. It's very hard to talk about autism or autistic experience without using at least some of this terminology. I've talked about this at length, but I think it's important to continue to talk about, especially as the language has been and is changing and continues to do so. In my university, my degree program, I found myself teaching instructors and other students, even those who were quite up to date in knowledge of the DSM, knowledge of psychology, psychiatry, even those who claim knowledge of neurodevelopmental conditions, were using the wrong language. And I found myself having, they wanted evidence for why I kept calling autistic people autistic instead of saying person or people with autism. Part of what I studied and part of what I wrote about for papers and even my last manuscript, my final manuscript, had to do with autism-related topics. Instead of just being able to concentrate on the research I was doing and the work I was doing, I had to stop and constantly explain myself. Obviously, I don't think my classmates and my instructors were doing that on purpose, but it was exhausting. They' d ask a question, they'd try to challenge me, even though they knew I was autistic, they'd challenge why I was using that language and how it wasn't appropriate. I would give them things to read and they would still clearly not go and read it and continue to challenge me. I found myself having to do that continually, over and over and over again over the past three years. I just found myself having to be that person who has to teach everyone about, almost the entire autistic community prefers identity-first language instead of person-first. Why is it? How many times do we have to say that? Do we have? I don't know what it is with autistic folks being just like. If I had a heart condition and I was trying to teach someone about an aspect of the heart condition, I wouldn't get this much pushback. It was disheartening, especially after seeing how much work had been done with anti-racist sort of work and all the EDI, equity, diversity, inclusion work that's going on on campuses these days, to see that neurodiversity, autistic topics are kind of way down on the list for most organizations. I know for a fact that I'm not alone in having to be that person who's like actually we don't use that terminology anymore and we haven't for literally decades, so catch up, please, it's not hard. Anyway, that's sort of an aside, but I just had to share that. To just say one more thing about language, autism scholarship has a long, long history of being firmly rooted in the medical model. All of the language that we use to talk about autism and autistic people literally arose from the medical model. The language surrounding autism was born in that model and in that world, that mindset. So, it's going to be a process. At the same time, the challenging of the language, the challenging of the medical model, is really not that new. It's relatively new, but I mean like it started in the 60s and the 70s. And here we are and I'm still having to make a case for why I, an autistic person, am calling myself autistic. It's annoying. That was a very long way to introduce this topic and I think it's time to talk about neural pruning, neural N-E-U-R-A-L pruning, and how that might relate to autism. So any discussion about neural pruning needs to start with talk about the nervous system. While there are several types of cells in the nervous system, there are two main cell types: neurons and glial cells. G-L-I-A-L, glial. Neurons are the transmitting cells, or can be thought of as conducting cells. In the brain alone, there are 86 billion neurons. These neurons conduct or pass information or signals to each other, while glial cells can be thought of as, at least in part, the connective tissue of the nervous system. Glial cells are non-conductive and provide structural and nutritional support for the neurons. They also include the immune cells of the nervous system, but neurons will be our main focus here. Importantly, the spaces between neurons, where information is exchanged in the form of substances called neurotransmitters, are called synapses. While we typically think of the brain when we talk about neurons, there are also synapses between neurons and muscle cells and neurons and gland cells. Without these synapses, there would be no information exchange from one neuron to the next. During a certain period of early brain development, from several weeks after conception to around eight months after birth, there is a period of very intense, very rapid synaptic overgrowth, which is adorably referred to as exuberant synaptogenesis. Synaptogenesis here simply means the formation of synapses between neurons. There's kind of an explosion of these synapses, way more than is necessary. While synapses form throughout a person's life, they don't form nearly as quickly or exuberantly as they do in this critical period of early development. Then, around two years of age, something interesting happens, and that is a period of rapid synaptic pruning begins. During synaptic pruning, synapses that are not used, or not used very much, are simply destroyed or removed. It's thought that this is the body's way of making sure that brain function is efficient or streamlined as we learn increasingly more complicated information and skills. More efficient brain function would also mean faster brain function. The end result is a brain with both fewer synapses, of course, and fewer connections between brain cells and brain regions. Also, while very early synaptic pruning shortly after birth is thought to be influenced mainly by genetics, a bit later on it's mainly influenced by our experiences. So the brain of a toddler who's getting read to a lot and who has a lot of enriching experiences with toys that help them learn and parents who are very engaged in helping the child learn and experience new things, their brains are going to be very different. Their synapses are going to be very different than a child who lives in the opposite kind of experience or environment as that. The brain's going to prune very differently depending on their experiences. As Jacquelyn Cafasso says in an article for Healthline quote whether or not a synapse is pruned is influenced by the experiences a developing child has with the world around them. End quote.

Google:

Once the brain forms a synapse, it can either be strengthened or weakened. This depends on how often the synapse is used. In other words, the process follows the use it or lose it principle. Synapses that are more active are strengthened and synapses that are less active are weakened and, ultimately, pruned.

Kristen Hovet:

End quote. I hope you got that, so it's the use it or lose it principle. Also, she says synapse s weird.

Google:

Once the brain forms a synapse.

Kristen Hovet:

Synapse? I guess I say synapse the British way, synapse, synapse, weird. Anyway, a significant body of research has shown a link between certain gene variants related to synapses and synaptic function and autism, and a growing body of research has appeared to confirm, some through postmortem studies, that autistic individuals have more synapses than their non-autistic peers. In other words, autistic individuals' brains experience reduced synaptic pruning. At least that's what the research appears to be showing. This means we have more connections between brain cells and between various brain regions. We have a whole whack of exuberant synapses that refuse to go gentle into that good night, to borrow a line from poet Dylan Thomas.

Google:

This under pruning theory, may help explain some of the common symptoms of autism, like oversensitivity to noise, light, and social experiences, as well as epileptic seizures. If there are too many synapses firing at once, a person with autism will likely experience an overload of noise.

Kristen Hovet:

End quote. So our autistic brains retain quite a lot of extra or what a lot of the research papers I read call redundant connections between neurons and brain regions. But this word redundant sounds quite judgy to me and comes from comparing said connections to the fewer connections in the non-autistic brain. So obviously the research is based on assumptions that the neurotypical brain is the right brain, the proper brain, the healthy brain, the brain that we should all aspire to be. But I think we need all the brains. I think we need all the autistic brains and the non-autistic brains and we need to stop comparing everything to the non-autistic brain, self, way, et cetera. It's quite likely that the reduced synaptic pruning and the resulting extra brain connections explain why it sometimes feels to me like I need to wait for signals to pass through a literal tangle of cognitive networks and also why my brain sometimes feels on fire with all of the electrical signals zooming around. If you did a scan of my brain during these moments, it would probably look like it was literally on fire. If this is all true, our brains are working harder and messages in our brains need to go through more channels, which takes longer. There's more processing to be done. Some have theorized that this slower processing underlies our tendency to think deeply, to be quote unquote intense, to think outside the box, and to be more inclined to take in a lot of details, favoring details over bigger picture perspectives. As Martin Silvertant states in an article for Embrace Autism, the, quote, increased communication between neurons and particular pathways can lead to amazing abilities. End quote. For example, being an autistic savant is likely linked with a bunch of synapses that didn't ever get pruned away. Also, synesthesia, known to be very common in brains with reduced synaptic pruning and very common in autistics and other neurodivergent individuals, is likely directly related to increased brain connectivity. Synesthesia is defined as a phenomenon where the activation of one sensory or cognitive pathway triggers the activation of one or more additional sensory and or cognitive pathways. A person with synesthesia might experience colors when listening to music, or they might experience certain tastes or smells when reading particular words. While only about 4% of the general population experiences synesthesia, almost a quarter of the autistic population does. This percentage might actually be higher as the research grows in this area. It's very common for an autistic person to not even realize they have synesthesia. They might not know there's anything different about their experience and the way they experience reality, and so they may assume that everyone has the same experiences that we now know to be synesthesia. This is certainly the case with me, in that I thought everyone has an explosion of sensory or cognitive experiences as a result of specific perceptions or thoughts. Let me explain, because that all sounds pretty abstract. But first, more lip gloss. My lips are getting dry. I don't know about you, but I'm one of those autistics that always has to have something on my lips and lotion on my hands. I cannot handle dry hands. I know that there's I have autistic friends who are the opposite. They can't stand sticky lotion on their hands. I don't like sticky lotion, but I need my hands moisturized at all times, or I'm like I can't touch anything, my hands are dry! I don't like dry lips either. It's like I just get really distracted and all I think about is hands! Or Lips. So synesthesia. I have mirror touch synesthesia, to give one example, which is when you feel the same or similar sensations as another person. So if I see someone get hit in the stomach, I'll literally feel pain or a jolting sensation in my own stomach. This type of synesthesia, this mirror touch synesthesia, has been associated with really high levels of empathy compared to the general population. It might be that people who are described as empaths simply have mirror touch synesthesia, basically a bunch of extra synaptic connections in the somatosensory and mirror neuron areas of their brain. I also have misophonia, which some think is a form of synesthesia. Misophonia is when you experience negative emotions or states, such as a state of major annoyance or the negative emotions of anger, fear and or disgust, when you hear certain sounds or like certain words or sounds made in certain frequencies. So with me, when I hear people blowing in that raspberry sound, like I can't even do it, it's so, making that sputtery spitting sound with their mouths, my brain just like feels like someone's gripped it from the inside and is sort of like rubbing it with steel wool or something. I don't know how else to describe it, and I feel like this kind of, I guess, disgust would be close to what I feel, the same kind of like heebie-jeebie feeling that some people get with the nails on chalkboard thing. So it's intensely unpleasant and like I just, if I'm around other people and it happens, I can sort of usually suppress my response, my reaction, but I'm feeling it and it's very unpleasant. I don't like it at all. Like I literally can't make the sound to show you or play you the sound because I edit my own podcast episodes. I'd have to hear that back and I just I don't want to do that to myself right now. I don't want to put myself through that. It's not fun. The other type of synesthesia that I didn't even know was synesthesia until I did the reading for this episode, it's called number form synesthesia. It's like a spatial form of synesthesia where you have like a spatial sense of numbers or like, as opposed to abstract. Numbers are almost like a literal map of numbers in your brain, that kind of like appear in your mind as though your perception or awareness is kind of focused into the middle of the map that it's sort of generating and other numbers span to the left and to the right, into the distance and air quotes, of course, on distance because it's in your mind, but whatever, it's really hard to explain. So let's say, if I'm asked to think about the year 1980, numbers to the left are older than 1980, with the year like 1900 being more to the left than like the year 1940, which would be like more here right. 1980, of course in the center, because I've been asked to think about 1980 and numbers to the right being closer to now and then spanning into the future further right. So it's like this very specific spatial orientation and it's like almost literally every time I'm asked to think about or I need to think about a number. I hope it makes sense and I'm wondering if you experienced that, like does anyone else? What's your synesthesia? I think there's like 80 some odd kinds and they're still, there's only been research kind of focused on a few, but more research is being done, so it's pretty exciting. Like many people with synesthesia, we didn't, like I said, know that our experiences are different than others. Like why would we know that? Like if, unless it's something that specifically talked about quite early on in our lives. We don't start learning about it until we're talking about something related to synesthesia and people react with shock or confusion or even fear, like really, what? That's weird! That's so weird! I think the most shocking to me personally was realizing that most people don't feel sensations that mirror or reflect what others feel. It's such a common experience for me and it's so core to my experience of the world, of others, that I can't believe that it isn't like human default mode. I'm trying to understand how others understand, because for me it's like a physical thing. I can understand, I can empathize, and I can feel what you're feeling, because I literally feel what you're feeling. If you're describing it, if you are showing that you're feeling something, let's say like you're doing this because your shoulder hurts, so my shoulder will start to feel weird or pain. Sometimes it's like what I would call a queasy sensation that is like radiating from my shoulder. Again, I know from talking to others that this sounds very strange and weird, but for many of you, you'll be like yeah, yeah, of course, obviously duh, like, that's what I experience, too, and I know for some people this mirror touch synesthesia specifically, is so strong that it's almost hard to be around people because you're not only feeling your own feels but you're feeling the other people's literal feels at the same time and that's exhausting. It's exhausting to feel everyone's feels and I would say mine is strong, but not strong to that degree. I mean I do have to spend a lot of time on my own. Maybe a lot of it is to do with the mirror touch thing, but because I think a lot of it happens without me being immediately aware, because it's so, like I said, it's so core to my experience of others that I don't think I necessarily always know that it's happening when it's happening. I kind of have to like take a step back and go what's this, what's going on? Oh yeah, this is my sensation and this here, that's your sensation and I'm feeling it. So it's, now my brain is going off into all these different thoughts about how autistic folks are impacted by these various types of synesthesia and how that is so core to what we call, what some call symptoms, what I prefer to call traits, autistic traits, that, um, yeah. So to sum up this section on synaptic pruning and synesthesia, I really like Silvert ant's words that with reduced synaptic pruning, quote, society gains an autistic person person in a smaller number of cases, people with synesthesia, and in rare cases, a savant, end quote. I really like that because it's sort of a positive way of seeing this and it's not like, oh darn, you have so many darn synapses. Ya poor thing, ya have billions of synapses. What ya gonna do? It's like you are you in part because of all your lovely, exuberant synapses and all the beautiful brain fires that your brain ignites and keeps the flame every single day. That is awesome, that is beautiful. I like that. I like that slant on it as opposed to. I think I especially like it because I've had to read all the very disappointing research on like yeah, we know these changes exist now, so maybe one day we can develop a neurologically based cure or intervention and just zap, zap, zap. No, thank you, I'm done with that research for a while. I don't want to read anything like that for a good long while and I said I wasn't going to get into the weeds and details. But dang it. Glial cells are interesting, and microglial microglia in particular might be behind a lot of the differences in synaptic pruning that are seen between autistic and non-autistic brains. So I can't help myself. I'll talk a bit about it here. But for any of you who are interested in reading more about microglia and autism, I'll include some interesting articles in the show notes. It includes work about glial cells called astrocytes, which are beautiful. As their name describes, astro, they're kind of like star shaped and, of course, well, not of course, I'm looking it up on my Merriam- Webster dictionary app. Astro combining form from astron, which means star, borrowed from Greek, so astrocytes are these beautiful star shaped cells in the brain. And anyway, I'm going to stop there before I go on another tangent. Microglial cells, or microglia, are the most abundant immune cells in the central nervous system and they have the ability to carry out phagocytosis, an amazing word. Phagocytosis means that they can eat, quote unquote eat, or engulf dead cells or damaged cell components or parts that form when the brain's experiencing inflammation, for example. Some of the components that microglia can engulf include weak or inactive synapses. Hello, synaptic pruning. This means that microglial cells need to be activated to clear out underused or unused synapses in the developing brain. It could be that autistic brains have differently programmed, differently behaving, or differently shaped or activated microglia, resulting in a different balance between neuronal excitation or firing, and neuronal inhibition or ceasing to fire, when compared to non-autistic brains. The increased excitation theory holds that autistic brains will experience more excitation, more connectivity in key regions of the brain, and this theory is in part supported by the known high rate of co-occurrence between autism and epilepsy and autism and seizure disorders. Neuronal hyperactivity or hyperexcitability underlie epilepsy and seizures, so there's a lot of overlap there. Some research has shown that some autistic brains have an increase in brain cell activity in some brain regions, while having a decrease in brain cell activity in other regions. This balance of neuronal excitation and inhibition seems to vary from one autistic person to the next, so it could be that the only thing we might be able to say for sure at this point in time is that autistic brains are characterized by marked differences in the balance of excitation and inhibition of neurons compared to non-autistic brains, and that we also have more synapses. That seems pretty clear. However, more research is needed to really determine the details of these differences. That is where I'd like to end, because I feel like I could just keep talking. I really like this topic and I do want to hear from you. Synesthesia is a very new word in my vocabulary. I have known about it for a couple years now, but it was like a huge epiphany when I first learned about it and when I learned that it's not the norm. I also see colors with different numbers and I thought that that was because of how I learned to count. We had this like penny system where pennies, circles were drawn with pennies, and that's why they called it the penny system. So they would have these charts showing the numbers and they would take a penny and draw circles over the numbers, so like the number two had two circles, so you'd have this like image in your brain, at least I did very much, like the number two always has two dots and each number has a color. And I don't know if that's my brain doing synesthesia stuff or if it's because when I learned the numbers, they were on these colored charts and they were almost permanently attached to the wall in elementary school, and so I'm not sure if my brain is just applying the colors of that chart or if I literally, if it's a synesthesia thing. Like I can't think of certain numbers without also feeling, sensing a color to go with it. And I just thought that that was normal. Like how else would I know unless, like there's so many things that we think and feel and process that we don't ever talk about and that they almost come out accidentally. And you might be talking about it one day and someone goes, huh, no, that's not what I experience, or whatever, and so you learn about it in these weird moments and then to find out later it has a name. So I'm not, I'm not weird. Like this is something that is normal for our community. Some of it's very beautiful, like I saw someone on social media who's autistic, who you give them your name and they come up with like this beautiful, like they have this beautiful almost like rainbow in their head of different colors, that matches each person's name, or like with a predominant color. So I think my name has purple in it. Yay, I love purple! But for that person, like for another person, it might be a totally different color scheme, but I just think that's beautiful, to like have this parade of colors that come along with language, like that's beautiful. I have it with numbers and they're kind of not exciting colors and like it's primary colors, which makes me think it's just from elementary school days. But anyway, I'd love to hear your experience of synesthesia. I don't know if I'm saying it right again. Like, help me Google. Synesthesia. What is it in Romanian?

Google:

Sinestezie.

Kristen Hovet:

Nice. Norwegian! Synestesi. I like that one. Okay, well, that's all I have for you today.

Speaker 3:

Thank you so much for being here. Until next time, bye.

Neural Pruning and Synesthesia in Autism
Understanding Syndromic Autism and Neural Pruning
The Connections Between Synapses and Autism
Autistic Brains and Microglial Cell Balance