Child Brain Development and Environmental Influences

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Welcome everybody . This week , we're going to be talking about the next step in our understanding of how our kids' brains develop . Last week , we talked about stressors and how they impact children during pregnancy . This week , we're going to start talking about our children's brain and emotional development , from birth until the period of two years . So there are really just two main points that I want you to take away from today . The first is that it is your genetics and your experiences that build your brain together . This harkens back to the diathesis stress model that we talked about previously in the video about the effects of stress on children while they're in the womb . The second thing that I want you to learn from today is that toxic stress affects your child's brain architecture . Those two things go together . Stress affects your child's brain architecture . Those two things go together . So , one , your child's brain is developed by a combination of their genetics and their experiences , and two , toxic stress affects your child's brain architecture .

Speaker 1 0:56

Big takeaways . So let's start for a second thinking about how your child's brain develops in the first place . And it builds on itself . That brain structure starts at the back of your child's brain , right the back of that brainstem , which is the more primitive portion of the brain and it curls up and over to the front of the brain where the more executive functioning takes place . So it builds on itself . While your child is very young , right An infant up to two years old they're simply starting to get the basics in place and their prefrontal cortex is not yet fully developed . I mean , that's not going to occur . Children don't reach their full adult mental capacity until they're 25 . And that's why you can't rent a car until you're 25 . So this is a very long process .

Speaker 1 1:47

One of the things that we have to keep in mind when we're talking about how our child's brains develop is that humans are altricial . That means that when human babies are born , they're essentially helpless , right ? It's kind of like when a baby bird is being born or when a rodent is being born , like when rodents are being born . They're deaf and they're blind . They rely on smell . When human babies are born , as you know , they rely on their parents for everything , and humans are kind of unique among altruistial species anyway , because it takes so long .

Speaker 1 2:18

The glide path of a human from infant to adulthood is very , very long . We just talked about the fact that your prefrontal cortex isn't fully online . Your executive functioning isn't fully online until you're in your early twenties . So what is the evolutionary benefit of that ? Because it puts an infinite risk . An infant human has to rely on their caregiver to provide everything to provide safety , to provide food , to provide shelter all of the things that a creature needs to survive . And also , if you think about it , not every parent is a great parent , I think , as we know , unfortunately . So human effort is kind of playing the lottery in terms of having a parent who is capable or interested in providing for them .

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So what's the evolutionary benefit to being not only altricial but also over such a long period of time ? Well , one hypothesis about why this is the case is that , by having this long glide path , it enables our brains to sort of take its time and develop really complicated structures . It enables us to have a really complex brain development that permits us levels of thinking that other species don't have Some evidence for . That is the amazing plasticity that our brains have during childhood . Your child's brain is extremely plastic , is moldable , is able to learn to build new pathways , to prune away unnecessary pathways , unnecessary pathways , and so , in the right hands , in the right caregiver's hands , this permits a child to spend a great period of time , with a very plastic brain that permits them to learn complicated things right , to have the ability to have complex emotional regulation , complex intellectual activities . If we put all that together , assuming that there's a good caregiver , then it's an amazing outcome . And not to mention the fact that , if we're thinking evolutionarily , it's a lot of work for the progenitor as well . For the parent it's a lot of work to have a child who is altruical , to have a child who depends on you for everything for up to 20 years or so , to have a child who depends on you for everything for up to 20 years or so . So the only real reason why that is the case is because the product at the end of that 20-year process is kind of amazing . Right , it's the human being , fully formed and well-formed , which is fantastic .

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The downside of that is that all powerful experiences shape our brain's architecture , shapes our emotional regulation , shapes our ability to have social interactions . So if you have powerful negative inputs , that's going to affect your brain architecture negatively , because our brains develop from the base up . They're not all developing at the same time . Some portions of the brain have rapid bits of growth , while others are kind of maintaining Some portions of the brain have rapid bits of growth , while others are kind of maintaining . One way to describe these different times , when the brain is either progressing rapidly or is kind of on hold , is saying that they have sensitive periods . So parts of your brain have different sensitive periods during which they're growing at various rates , and during those sensitive periods that portion of your brain is especially susceptible to certain stresses , to certain stimuli . Right , it can be a positive stimulus or a negative stimulus , but during these sensitive periods is extremely susceptible to modification based on the environmental stressors that it experiences . So in terms of the power of the human brain , it's kind of fascinating .

Speaker 1 5:51

We have 22,000 genes in our genome , all of which are going to be expressed at some point during the development of our brain , like we talked about when we were talking about the diathesis stress model . If you think about your genome as sort of this sheet music , then the experiences that we have in the environment allow us to make some notes . Right , we're going to play this section faster , that section slower . You know , this section louder , that section softer . Those notes on our sheet music is the changes in the expression of those genes . So as our brain develops , the way that the architecture unfolds is being changed by the epigenetic responses to the stressors on the genes in our genome . So , as we're thinking about brain development and we're thinking about how our brain reacts , as it's growing , to the experiences in the environment , our brain , our body is preparing us for the environment in which it thinks we're going to have to exist . That's how the changes are made , that's how the body adapts .

Speaker 1 6:47

So , as we talked about in the prior episode , if an infant is being placed in situations of extreme neglect , for example , the brain is preparing itself to experience life in extreme neglect . That is an allocation of resources that is not necessarily optimal , right , that's not optimal for a child who is going to live in this world hopefully not in a situation of extreme neglect . It has trade-offs and that trade-off is going to have some negative implications for a child as they grow and mature . So , ultimately , we develop approximately 40% more neural connections than we're going to wind up having when we're adults , because what happens is the neural connections that we don't to wind up having when we're adults , because what happens is the neural connections that we don't need are pruned .

Speaker 1 7:32

When we aren't using neural connections , the brain says well , this is not an efficient allocation of resources and it gets rid of those pathways . Instead , it takes the available resources and it strengthens and speeds up the neural pathways that are used the most . It's kind of a use it or lose it situation , and this is what . That use it or lose it situation kind of looks like You've got billions of brain cells . Those are the brain cells called neurons and they send electrical signals that communicate with each other . Now , as these connections form circuits , they become the basic foundation of your brain's architecture that we've been talking about . These circuits , these connections , they grow at this rapid pace and they're reinforced by repeated use . Connections that are used more often grow stronger and more permanent . But connections that aren't used that often , they get pruned , they start to fade away . Low-use circuits create these really fast lightningick pathways . First you get these simple circuits that form . They provide a foundation for more complex circuits that get built on later . Throughout the process , neurons form strong circuits and the connections for things like emotions , motor skills , behavior controls , logic , language and memory , and that all happens during this early critical period of development that we're discussing .

Speaker 1 8:49

Here's a pretty fascinating example of that concept in rats . Now , a lot of the studies that I see when I'm trying to get prepared for one of these videos are rodent studies , because you can do things with rodents and experiments that you can't do with humans . But in this example we're talking about rodent auditory development . Now , initially , rodents are able to hear all sorts of different frequencies . This diagram that you're looking at shows how early experiences , extreme early experiences , can disrupt a rat's ability to hear different frequencies . Now , early on , if you look towards the left at A , you'll see that there are all these different colors right and you have this big red color that's circled . We're going to be looking at that more in a minute . But next to the red you see these different colors yellow , greens , blues . These are the various frequencies that a rat can hear and you can see the different hertz levels on the right in that bar graph . Now , early on , the rat can hear all sorts of different frequencies , can hear that entire range . Look at B . But if , for whatever reason , a rat is no longer provided with the full range of those frequencies , the brain is going to stop being able to hear them , literally stop being able to hear the full range of frequencies . And so , as you get to see on the right-hand side , when they've been exposed to these extreme early experiences , the rat's brain can no longer hear the full frequencies . You don't have all the blues , you don't have the greens , you're really just left with that red area . That's the majority of what's left , because that's all the rats can hear . Okay , now here's the interesting thing it's not an efficient allocation of resources for the brain to remain capable of hearing the frequencies that it's never gonna hear .

Speaker 1 10:35

That same concept applies to us . It applies to your kid . If your child is not using certain neural pathways , then those pathways are going to shrivel up and eventually be pruned . The pathways that the child uses a lot are pathways that are going to be strengthened Think about this as a co-parent that are going to be strengthened . Think about this as a co-parent . Which pathways are you encouraging to grow ? Are you encouraging neural pathways that are positive , that are the result of good parenting , to emerge ? Are you encouraging those pathways to be strengthened , to be sped up , or is your child not having the kinds of experiences that we would hope a child has ? Is your child focused primarily on dealing with stressors , on having their body receive environmental stress , fear being neglected and realizing that they're not going to be receiving the assistance that they need . And so other neural pathways that are the result of neglect are being reinforced and sped up .

Speaker 1 11:34

Even though your child may be too young to understand what's going on , even though your child hasn't developed speech , even though you don't necessarily have the concept that your child actually knows the kinds of things that are being said or done around them , your child feels it right . Your child's body reacts to stress . Your child's body reacts to conflict , even though they can't necessarily tell you that there's conflict going on . Even if 10 years from now , they wouldn't be able to remember that they were exposed to co-parenting conflict or physical arts of altercation or yelling and screaming or neglect and things like that . Even though they won't be able to verbalize those things to you as they get older , their body remembers it . The neural pathways that are essentially selected will remember it . The neural pathways that are pruned and gone that would have been positive . Those are gone .

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So , as you're interacting with your child , as you're interacting with your co-parent in the presence of your child , think about what you are doing to the presence of your

Impact of Stress on Child Development

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child .

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Think about what you were doing to the development of your child's brain architecture . There are good things and bad things that we can do to help our child's brain develop . The things that are bad for you as an adult , the things that cause you stress , that makes your heart race , that makes your blood pressure go up , that makes your heart race , that makes your blood pressure go up , that makes your palms sweat , that gives you that sense of dread those are all things that impact your child too . Just because they're too young to tell you that they're feeling it doesn't mean their body doesn't feel it . So I'm going to get more into some details of this and some studies that I think are quite fascinating as we get into further podcast episodes . In upcoming episodes , we're going to talk about the positive things that you can do that can have good results on your child's brain development . We're also going to talk about things that are negative for your child's brain development . In the meantime , I hope everybody has a great week and I'll talk to you all soon . Thanks ,