Transcription
Well, 6 months ago I gave birth to my second child, Dylan. And as a mom and as a neuroscientist, I can't help but see my son through two lenses, as a bundle of joy and a science experiment in diapers. It's fascinating to witness his identity emerge at each stage of development.
The brain is sculpted like clay by our experiences over the course of our lives with the genes providing the raw material as well as a few pre-formed contours. And as our neurons begin to wire up, the clay hardens but never completely, so there's always room for change. A baby is born with billions of neurons with trillions of connections that are eventually pruned away with the most salient connections retained and the less of the rest allowed to wither. Identity in a way, like information, is a matter of differentiation. Of defining ourselves by what we're not or by what we do or don't reach for.
That's my son. At around 18 months a toddler can pass the mirror test. This is the first outward sign of self-recognition. If one placed in front of a mirror they rub a red mark that was covertly placed on their face. This is evidence that they recognize the image as themselves rather than someone else. That's actually my daughter Hannah at 2 months passing the mirror test way ahead of schedule. And the other species that are known to pass the mirror test are great apes, dolphins, orcas, magpies, and a single very precocious elephant.
So, self-recognition and identity formation in humans is reinforced as language emerges. So, babies go from identifying nouns like mommy, doggie, dolly to adding possessive pronouns, my doggie, my mommy, my dolly. And later they begin to identify themselves with adjectives, right? I'm smart, I'm friendly, I'm endowed with magical superpowers. Identity is clearly a verb, not a noun. Formed as our brains interact with our environments.
So, today I'm going to talk to you about how our brains make us who we are. And one way I explore this is by studying psychiatric and neurological patients with disorders of identity. Because when the brain goes wrong, it gives us an idea of how it's working the rest of the time when we take it for granted.
So, here's an extreme case. Uh this is a man who in his mid-40s developed pedophilia, which is unusual. Usually it manifests earlier. But in this case, the night before he was going to be sentenced for molestation he checked himself into a hospital for severe headaches. They did an MRI and they found that he actually had a large tumor in his right prefrontal cortex. Specifically in the orbital prefrontal cortex, the part of the brain just above the eye sockets and it's involved in our personality and impulse control. And this made sense because the man had stated that whenever he tried to restrain himself, the pleasure principle overrode. So, they surgically removed the tumor and his symptoms went away. He was allowed to return home uh where he was living with a young stepdaughter. Things were fine until about a year later the symptoms came back. And sure enough the tumor had grown back. So, a lot of neuroscience is about correlation, right? Showing that certain brain areas are active during certain behaviors or thoughts. But in this case we're talking about causation. Changes in the brain directly causing changes in personality and behavior.
Another condition that I study that has problems with impulse control is borderline personality disorder. Now, this is characterized by people who have instability in their self-image, in relationships, in their emotions. Um they also have a lot of impulsivity, things like reckless spending and driving and shopping and uh self-harm, substance abuse, binge eating. Now, this might sound like a typical weekend for Justin Bieber. But we have to resist the temptation to make these armchair diagnoses. People with borderline personality disorder make for dramatic film and television stories but they're suffering and so are the people around them.
So, I actually conducted a study where I compared people with borderline personality disorder to patients with orbital prefrontal cortex lesions like the man I just spoke about on a series of neurocognitive and personality tests because they both seem to display similar symptoms. And what I found is that orbital prefrontal cortex dysfunction is the driver of the impulsivity in the borderline patients. What this means is that we can begin to target treatments at the underlying neural circuitry uh that drives the core symptoms of borderline personality disorder like their impulsivity or their emotional dysregulation rather than treating the overarching disorder itself. So, the more we understand about how the brain works the better we can treat disorders of identity.
The final condition I'm going to talk about is dissociative identity disorder. Now, this used to be called multiple personality disorder. And it occurs when psychological processes that are normally integrated become segregated. And it creates a a feeling of disintegration or fragmentation in a person's identity. So, it's at the extreme ends of a continuum of dissociation. We all experience mild forms of dissociation. So, when you're for example engrossed in a really good book and you lose your sense of time and place and self or you return home after a very long drive and you realize your mind was wandering and you don't really remember any of the drive. In a way, self-driving cars have actually been around for quite some time.
But this disorder can be very disturbing to people. But but dissociation itself can also serve an adaptive uh function. It can be a defense mechanism against trauma, right? It can help people separate out these anxiety-provoking memories or emotions so they can function adaptively in their daily life. But at the very extreme ends when people there are cases where people actually have their identity separate out into these different dissociative identity states. They usually have a traumatic identity state where they have access to their own disturbing traumatic memories and a neutral identity state where they have selective amnesia for those memories.
Now this disorder used to be thought of psychologists didn't take it for they thought it was a made up. But actually neuroscience can confirm that it's a real disorder with an underlying physical basis that can't be faked at the neural level. So, for example one study showed that when they looked at people in these different identity states they had different physiological reactions to memory scripts that were being read to them uh when they were in these different states. So, when they were in the traumatic identity state and they had access to the traumatic memories and the memories were read to them they would get increased heart rate um they'd have galvanic skin response increase uh and they would have emotional reactions. But they didn't have this when they were in the neutral state. So, that means who we are might be determined by how our brain reacts.
Then they did neuroimaging they found that when people were in the neutral identity state it created a broad areas of activation in the brain, all these areas here in red. And when they were in the traumatic identity state, there were far fewer areas of activation. So, what does this mean? It means that suppressing traumatic memories actually takes more brain activation than remembering them. And being in a in a dissociative identity state is like being in a completely different brain state or you can think of it like running a virtual PC on a Mac computer.
So, this is actually uh EEG of a patient who could see in one state and not see in the other. At least she claimed this. Now, try it for yourself. Keep your eyes open and try not to see. Right? It's virtually impossible. But in this case, they looked at brain activation in her primary visual cortex in response to a flashing checkerboard image that she was viewing. And what they found is this pattern on the left was her activation in her visual cortex in response to the flashing checkerboard pattern. But in the on the right, you can see that when she was in her blind state, she did not have any reliable visual cortex activation in response to this image. So, she really couldn't see. Now, this means that the suppression of visual information is happening very early in the sequence of processing in the brain, perhaps even at the level of the thalamus. And I actually tried to bring her in to my lab so I can run some tests on her but she recovered. She integrated her identities, which was really good for her but not for my study. Uh But what her case her case reveals the brain's plasticity. Right? Many of these conditions are amenable, they respond to therapy. So, they either resolve completely or people can learn uh ways to adapt and live with their symptoms. We're all malleable, right? We can change. If you change your thoughts and behaviors, it can change your brain and ultimately change who you are. And understanding the brain allows us to influence it more directly.
So before I finish, I want to give you a taste of what's currently achievable with brain-computer interfaces. So we're learning how we can actually go in and change who we are with the press of a button via neural prosthetics. So for example, deep brain stimulation is uh common treatment for people with movement disorders like Parkinson's, but it's now being used to treat people with with refractory um or treatment-resistant severe depression and obsessive-compulsive disorder. So these are what the electrodes look like and what they look like when they're implanted. And now remember, this is a sort of last resort. Uh deep brain stimulation is used when they've failed medications, when they've failed psychotherapy, even electric shock therapy. So you can think of electric shock therapy is like turning your computer off and on again if there's a problem. Whereas deep brain stimulation is like force quitting a specific application. It's much more targeted. Now you might still think this is harsh. This is neurosurgery. But actually the alternative used to be to go in and and lesion the brain, damage it. But in this case with deep brain stimulation, it's reversible, it's adjustable, it doesn't damage the brain. And amazingly, about 40 to 50% of people with treatment-resistant depression and about 60 to 70% of people with treatment-resistant obsessive-compulsive disorder show significant improvement after deep brain stimulation.
This is actually a patient uh in the operating room when they first turn on the the electrodes. Her whole face lights up and she says she feels happy. Then, when she doesn't know it, they turn the electrodes off and her she actually goes right back down to a flat affect. So again, this is going from correlation to causation, right? We're directly stimulating the brain to manipulate people's emotions. So be nice to neuroscientists because we have our finger on the button. And these simple electrodes are just the Model T Ford of what's to come. As our understanding of the brain improves, so will our ability to treat disorders and also to design cognitive enhancements. And and brain-computer interfaces that could potentially increase the processing speed of our brain, uh expand our memory capacity, our attention span, manipulate our thoughts and emotions, even decrease our need for sleep.
Now this might sound great, but there are also ethical considerations, right? Who can afford the implants? Will uh they be sort of just cosmetic like Botox injections for the brain? Or will the effects give us a real uh will they enhance us give us a kind of performance like like kind of performance-enhancing drugs for athletes? And if so, are there going to be two classes of citizens, right? Enhanced and unenhanced? And what if someone can hack into your neural implants and manipulate your thoughts and behaviors, right? So these are right now academic debates, but my children might actually have to confront these questions first hand.
So my my 6-month-old son and 3 and 1/2-year-old daughter, the half part is very important. Uh they're still in the early stages of brain development, but it's exciting to imagine the advances that neuroscience will make by the time their prefrontal cortices are fully developed in about two decades. And the possibility to enhance their mental capacities. Not that they would need it, of course. Uh but in the meantime, uh these discoveries are already allowing us to to understand ourselves better and to come up with improved treatments for disorders of the brain.
The brain is both um delicate and robust. You know, it's easily damaged, but it's impressively able to heal. And each of us, regardless of age or state of health, is midway through a process of self-discovery and self-creation as our brains are continually interacting with our environments um and being shaped by them and they're being kind of guided by our genes and forming our identities. So each of us is a work in progress until our very last breath. And this this perspective helps me go through life with more compassion and appreciation for the people I meet. So if I have a really good interaction, I remind myself it's their brain I'm loving. And if it's negative, I remind myself that myself that we're not all wired the same. And this helps me interact with everyone from impulsive teenagers to demanding three-agers uh to people with severe identity and personality disorders who I can help treat as a clinician, a researcher, and a mom. So remember, you are your brain, but you also have a role in shaping it. Happy sculpting.