Trauma's Echo: Genes, Brains, and Your Lifetime Impact | NOVA | PBS

Hinzugefügt: 2026-05-04

[00:00:00]- People in the world suffer from traumatic events.

[00:00:03]And these traumatic events aren't just a one-time change in their brain and their body.

[00:00:07]It actually continues for seemingly their lifetime.

[00:00:11]- [Heather] Bianca's research is inspired by her upbringing.

[00:00:15]- My parents, my biological parents were also foster parents, so I had foster siblings and adopted siblings growing up.

[00:00:21]Only now as a scientist I realize that that motivates a lot of the questions that I ask.

[00:00:26]How do we understand what happens when kids are born into trauma and optimize what we do have for better generations?

[00:00:35]- [Heather] One insight comes from an event during World War II.

[00:00:40]- At the end of World War II, the Netherlands were cut off from food by Nazi troops because they decided to protest through the country.

[00:00:47]And during this period of time, it created a man-made famine.

[00:00:50]There was starvation, death, there was trauma.

[00:00:54]- [Heather] Not only did those who suffered during the famine experience health problems, but some of their children and even their grandchildren had metabolic issues.

[00:01:04]- So people began to ask, how does an experience of a parent, of a grandparent, change offspring?

[00:01:13]- [Heather] Researchers began to discover that your environment and your experiences can change the way your genes are activated in your body and in your brain.

[00:01:24]- It's not like you get your genes and it's set in stone.

[00:01:26]They're constantly changing based on the environment.

[00:01:29]- [Heather] To see this in action, Bianca studies mice.

[00:01:33]- We're able to map the whole genome of mice, target certain areas of that genetic code, and use them to answer the important questions in science.

[00:01:43]- [Heather] So how could stress and trauma alter the biology of the mice's offspring?

[00:01:50]To find out, Bianca paired the smell of almond with an electric shock.

[00:01:56]- Because mice really navigate the world and rely heavily on the sense of smell, we use olfaction, pair it with the light foot shock, and we observe changes in the brain and changes in behavior.

[00:02:07]- [Heather] She noticed that something inside of the mice's noses changed.

[00:02:13]- We're able to look at the cells in the nose that only respond to almond.

[00:02:17]And what we observe is that after the light foot shock and the presentation of almond coinciding there are more cells in the nose that express the almond receptor.

[00:02:27]It's as if something in the milieu of the nose says, "Almond's important in this environment, we need more cells like you."

[00:02:34]- [Heather] Mice grew more cells that responded to the smell of almond.

[00:02:39]- Each one of these three dots you see here, these are neurons.

[00:02:43]They're cells that can respond to the almond smell.

[00:02:47]These red dots are cells that were born after the presentation of odor and shock.

[00:02:53]And this cell right here, this red-and-green cell, is a cell that was born after the presentation of almond and shock that also responds to almond.

[00:03:02]This is the cell that we wanna look at to see what information is inside, because we see more of these after the odor and shock pairing.

[00:03:11]- [Heather] Remarkably, these changes were actually passed down to the next generation.

[00:03:17]- The offspring, the kids of the parents that were shocked with odor were born with more cells that express the almond receptor, which means there's a memory that somehow is maintained in sperm and egg through implantation and represented in offspring.

[00:03:35]It is as if we are observing a change in evolution over the time span of one generation.

[00:03:43]And I just think that's fascinating.

[00:03:46]Because we as humans know how environment and how traumatic events change people.

[00:03:54]Just being able to take the science of that and being able to show that, we're just justifying what we already know as humans, what society has known for a long time, what individuals know.

[00:04:04]We just wanna bring that to an undeniable truth.

[00:04:11]- Our brains are not static.

[00:04:13]We try to make sense of what's happening right now, but we also try to make sense of what happened a long time ago, and to have, like, this grand picture of our life as a trajectory.

[00:04:27]- Our ability for conscious awareness it's a magnificent ability, this ability to reflect on our own minds, but it also leads us astray.

[00:04:36]- I have memories, plans, I have these feelings of agency over my actions, but what the science itself is telling us is that these things aren't necessarily bound together.

[00:04:46]Different aspects of the self can be manipulated or even taken away altogether.

[00:04:52]- Your biology and the choices you make are all molded by your social interactions and even your family history.

[00:05:00]And yet we feel like we have control, like we have agency, right?

[00:05:13]- An agent is somebody that is the author of their own story.

[00:05:19]But actually most of what's happening in our brain, we are not conscious of.

[00:05:23]And I think this gets you starting to think, "Wait a minute, you know, is really everything under my control?"

[00:05:31]- [Heather] Neuroscientist Uri Maoz is putting our sense of control to the test.

[00:05:37]We feel like we're in control, but where exactly does that feeling come from and how does it work?

[00:05:44]- Ah, here you are.

[00:05:47]Hello. - Hello.

[00:05:48]Thank you very much for joining us agentically and out of your own volition.

[00:05:54]- (chuckles) Of course.

[00:05:54]- Before we start- - Mm-hmm.

[00:05:56]- let me give you this envelope.

[00:05:58]- Okay?

[00:05:58]- Please don't let anybody touch it and- - Okay. - don't look inside, but we'll need it for later on.

[00:06:04]- For later, okay. I'm gonna put it in my... To show me how my sense of control isn't always what it seems, Uri kicked things off by trying to get me to question my ability to choose by using a magic trick.

[00:06:15]- So where would you like to sit?

[00:06:18]- Where would I like to sit? - It's really up to you.

[00:06:19]- [Heather] It's really, I have a choice? - Wherever you want.

[00:06:21]- [Uri] You have a choice.

[00:06:22]- All right, so I'm gonna sit here.

[00:06:24]- You're gonna sit over there.

[00:06:25]Okay. - Yes.

[00:06:25]- So how about just before you sit down, if you don't mind.

[00:06:28]- [Heather] Mm-hmm.

[00:06:29]- Let's see. Let's see what this says.

[00:06:33]- Oh my god. Okay.

[00:06:34]- So... - So then that one obviously says the same thing, right?

[00:06:39]- No? - Let's check and see what this one says.

[00:06:42]This one says... - Oh, come on.

[00:06:47]- Okay. - So I'm that predictable?

[00:06:49]You don't even know me yet.

[00:06:51]- So if this is- - I really don't know how he did that.

[00:06:54]I'm not totally convinced, but I'm starting to question how do I know when I have made a decision?

[00:07:02]So to find out what's actually going on in the brain when our sense of control is in question, I took a look at a trial designed by postdoctoral researcher Alice Wong.

[00:07:13]A volunteer from the lab, Tomas, is being fitted with a transcranial magnetic stimulation device, TMS for short.

[00:07:23]It generates a strong magnetic field that can send signals to your brain.

[00:07:28]- The idea is that you stimulate the brain using a focused magnetic field, and if you stimulate that in the right part of the motor cortex, it's a part of the brain that actually controls your fingers.

[00:07:42]It's like you're pulling on a string here.

[00:07:43]Every time you pull at the finger goes.

[00:07:47]- [Heather] With the device hooked up, the researchers can make his finger jump involuntarily by sending a signal to his motor cortex.

[00:07:56]- We're gonna be locating the spot of your motor cortex that moves one of your fingers.

[00:08:03]How about that? - That works.

[00:08:05]That was a pinky movement up.

[00:08:07]- [Alice] Okay.

[00:08:08]- [Heather] Sometimes they ask him to move his finger on his own.

[00:08:12]- Could you replicate the movement if in, that you felt- - It was something like this.

[00:08:18]- [Heather] Remarkably, by recording the small electrical signals that travel from his brain down to his finger muscles, Alice and Uri can pinpoint the exact moment that Tomas's brain has initiated a movement, almost 50 milliseconds before he actually moves.

[00:08:36]With this information, it's as though they can predict his movement slightly before it actually happens.

[00:08:44]So now his sense of agency is about to be put to the test.

[00:08:48]- [Alice] Who initiated the movement?

[00:08:49]- [Tomas] It was me.

[00:08:51]- [Alice] How much agency did you feel over the movement?

[00:08:53]- Quite a lot. - Full agency. Okay.

[00:08:57]- [Heather] Normally the researcher isn't in the room and all the questions are conducted by the computer.

[00:09:03]- [Alice] Who initiated the movement?

[00:09:07]- I don't know.

[00:09:10]- How much agency did you feel over the movement?

[00:09:13]- I would say some agency.

[00:09:16]- [Heather] In some instances, just as Tomas decides to move his finger, the researchers use the magnetic field to make his finger move.

[00:09:25]- [Alice] Who initiated the movement?

[00:09:27]- I really don't know.

[00:09:29]- [Alice] Okay.

[00:09:31]How much agency did you feel over the movement?

[00:09:35]- A little bit.

[00:09:36]- [Heather] So even in the instances when Tomas really did decide to move his finger... - [Alice] How much agency did you feel over the movement?

[00:09:44]- No agency at all.

[00:09:46]- [Heather] He didn't always feel like he was in control.

[00:09:50]So after the experiment, I was excited to hear the results.

[00:09:55]- When Tomas initiated the movement himself, yet we intervened with the TMS, Tomas said, "That wasn't me.

[00:10:03]I didn't initiate the movement. It was the computer."

[00:10:07]He thought that the computer initiated the movement or it was both of them, or he wasn't sure, but he almost never said that it was him.

[00:10:14]- So what do you think is going on there?

[00:10:16]How is this happening?

[00:10:18]- You know, we walk around and we feel like, you know, we are the authors of our actions and so on.

[00:10:22]And you can see with just a little bit of messing around, it tends to fall apart.

[00:10:27]- [Heather] It's fragile, like our sense of self- - Yes.

[00:10:29]- our memories, our sense of agency.

[00:10:31]They're all things that our brain evolved over time, but they're fragile- Yes.

[00:10:35]- [Heather] and they can be manipulated under the right circumstances.