Chapter 16: Psychopathology: Biological Bases

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She is leaving the building.

It sounds like such a mundane sentence.

Just a boring flat observation.

It does.

It sounds like something a security guard might mutter into a radio.

But I want you to really put yourself in the shoes of a 19 year old college freshman.

Let's call her Eleanor.

She's bright.

She's packing up her bag after a long lecture.

Maybe thinking about grabbing a burger with friends or, you know, stressing about a midterm.

Life is normal.

Totally normal.

She's optimistic.

And then suddenly, just completely out of nowhere,

a calm, disembodied voice speaks that sentence right into her ear.

She is leaving the building.

And the really terrifying part is that the room is empty.

Exactly.

She looks around.

No one's there.

She brushes it off, you know, thinks maybe she's just tired or over caffeinated.

We all had those moments.

We have.

So she walks home, maybe walking a little faster than usual.

She puts her key in the lock and there it is again.

Clear as day.

She is opening the door.

That is the moment where the world just fractures.

It's the beginning of the loss of self, really.

It is.

It's like a narrator has moved into her skull, just dispassionately commenting on her life in the third person.

And for Eleanor, this wasn't a one off event.

It was the beginning of a slide into absolute hell.

The voice didn't stay neutral.

It became plural voices.

They became menacing.

They started, well, they started giving orders.

And this is the classic,

absolutely heartbreaking onset of schizophrenia.

As we see in the source material, it just destroyed her social standing completely.

Completely.

Her friends pulled away because she was muttering to herself or, you know, reacting to things they couldn't see.

She eventually threw a glass of water at a professor because a voice told her to do it.

She went from Eleanor, the promising student to Eleanor, the outcast in just a matter of months.

It's a terrifying story.

It is, but it's the perfect entry point for what we're doing today.

We are taking a deep dive into chapter 16 of behavioral neuroscience titled psychopathology, biological basis of behavioral disorders.

We are looking at the source material from Breedlove and Watson to answer one fundamental question.

What was physically happening inside Eleanor's brain?

And that focus on the physical, on the brain rather than the mind, that is the crucial distinction here.

For centuries, stories like Eleanor's were treated as, you know, spiritual failures, demonic possessions, or just weak character.

Today,

our mission is to strip away all that superstition and look at the machinery.

We're going to look at the biology, the chemistry and the structural glitches that create schizophrenia, depression, anxiety and OCD.

It's the shift from the abstract to the concrete, isn't it?

We're moving from why is she acting this way to which specific neurons are misfiring.

Exactly.

So buckle up.

We have a lot of ground to cover from the history of syphilis to the modern genetic tracking of eye movements.

Let's start with that history because to really understand where we are now, you have to realize just how lost we were only 100 years ago.

The text paints a pretty grim picture of mental hospitals at the turn of the 20th century.

I think we have this kind of this movie version of asylums, but the reality described here is just it's overwhelming.

Grim is an understatement.

If you walked into a psychiatric asylum in, say, 1900, it would have been overcrowded, loud and frankly completely hopeless.

But what's so interesting for us looking back is that a huge chunk of those patients, thousands of them were suffering from the exact same condition.

They called it paralytic dementia.

That name alone, paralytic dementia, it just sounds like a deaf sentence.

It sounds heavy.

What did that actually look like in a patient?

It was a very specific and tragic profile.

You'd see a sudden onset of delusions and not just, you know, I think people are watching me, but real grandiosity.

These patients thought they were kings, prophets or millionaires.

They were euphoric, incredibly impulsive and had terrible judgment.

They were completely losing their grip on reality.

But there was a physical tell, right?

A clue that this wasn't just a mood swing or some kind of personality shift.

Yes, the eyes.

It's called the Argyle Robertson pupil.

It's a fascinating diagnostic detail that feels like something out of a Sherlock Holmes novel.

How does it work?

Well, normally if I shine a flashlight in your eye, your pupil constricts.

It gets smaller to block the light.

That's a basic reflex.

Sure.

In these patients, that reflex was just gone.

The pupil wouldn't react to light at all.

However, and this is the really weird part, if you ask them to look at something close to their face, like your finger.

Then the pupil would constrict.

Yes, it would constrict a focus.

So the mechanism still worked, the muscle could still move, but the specific wiring for the light reflex was broken.

Exactly.

It was a very specific neurological glitch.

And for years, doctors just shrugged and said, well, these people have weak souls or they lived a sinful life.

But in 1911, a Japanese microbiologist named Hideo Noguchi changed everything.

He analyzed the brains of these patients after they died.

And he found something that shouldn't be there.

He found treponema pallidum.

Correct.

The Spirochet, the bacteria that causes syphilis.

So this wasn't madness in some kind of poetic sense.

It was a sexually transmitted infection.

It was syphilitic psychosis.

The bacteria had physically invaded the brain tissue, literally eating away at the neurons.

And the reason this is our starting point, this is so pivotal, is what happened next.

Right.

Once we discovered antibiotics, specifically penicillin, this entire category of mental illness virtually vanished.

That is the light bulb moment for the entire field, isn't it?

You go from these people are cursed to these people have a bacterial infection.

Precisely.

It was the moment the medical community realized that severe behavioral disorders could have a tangible biological cause.

It opened the floodgates.

If paralytic dementia is just a germ.

Maybe schizophrenia is a virus, maybe depression is a chemical imbalance.

It shifted the entire paradigm to looking for the biology behind the behavior.

And when we look at the scope of these disorders today, the numbers in the chapter are actually shocking.

I think we all have a tendency to think of mental illness as something that happens to someone else.

Right, something that happens on the news or in movies.

But the epidemiology suggests we are all much, much closer to it than we think.

The data is undeniable.

We should look at table 16 .1 in the text.

According to the source, more than one third of the U .S.

population reports symptoms matching a major psychiatric disorder at some point in their lives.

One in three.

One in three.

That's someone in every family or every friend group.

If you look around a dinner table of four people, statistically, one of you has dealt with this.

It is.

And the demographics tell us a lot about the biology, too.

For example, depression is significantly more prevalent in females,

drug dependency and alcoholism, much, much higher in males.

Why do we think that is?

Is it purely biological or is there a social element to that?

It's likely a mix, of course, but the chapter really focuses on the biological onset and the timing is very specific.

Schizophrenia almost always strikes in young adulthood, just like it did for Eleanor.

Yeah.

It rarely appears before puberty or after age 30.

Which is particularly cruel because that's right when life is supposed to be taking off.

You're leaving home, starting college, starting a career.

It is.

Depression tends to peak a bit later, usually between 25 and 44.

And cognitive impairment, is obviously mostly over 65.

So these things track with our biological development and aging.

The brain is vulnerable in different ways at different stages of life.

That's right.

So let's go back to Eleanor and really unpack schizophrenia.

It is probably the most misused word in pop culture.

You hear people say, oh, the weather is so schizophrenic today, meaning it's changing back and forth.

Or they think it means split personality.

Right.

The Jekyll and Hyde trope.

We need to clear that up immediately.

The term was coined by Eugen Bloyler in 1911.

It comes from the Greek she -sign meaning to split and frion meaning mind.

But Bloyler was absolutely not talking about multiple personalities residing in one body.

So what exactly was splitting?

He was referring to dissociative thinking.

It's a splitting of the logical structure of thought.

It's an impairment in how concepts are connected.

In a healthy brain, A leads B leads to C.

In a schizophrenic brain, A might lead to purple, which leads to fear.

The logic is just.

It's fractured.

It's a disintegration of the self -continuity.

The text breaks down the symptoms into two big buckets, positive and negative.

And I remember when I first learned this, I found it confusing because positive usually means good.

Yeah.

In medicine, you have to retrain your brain on those words.

Positive just means present.

It refers to behaviors that have been added to the person's experience, things that shouldn't be there but are.

Like the voices Eleanor heard.

Exactly.

Hallucinations are a classic positive symptom.

Delusions, like believing the FBI is tracking your dental fillings, are positive symptoms.

Excited motor behavior where someone is moving frantically or pacing, that's a positive symptom.

I want to pause on the hallucinations for a second.

The text mentions the movie A Beautiful Mind about the mathematician John Nash.

It's a great movie, but.

But it gets the symptoms wrong.

It's a major misconception.

In the movie, Nash has these incredibly vivid visual hallucinations.

He sees a roommate, a little girl, a government agent.

He sees them as clearly as I see you.

That is pure Hollywood embellishment.

The source material is very, very clear on this.

Visual hallucinations are actually quite rare in schizophrenia.

The hallucinations are almost always auditory.

Hearing voices.

Hearing voices.

Why is that?

Why the ears and not the eyes?

What's the thinking there?

Well it likely has to do with the brain's language centers.

The leading theory is that the brain is misinterpreting its own internal monologue as coming from an external source.

It's a failure of what we call source monitoring.

You think your own inner voice is someone else talking to you.

That makes a lot of sense.

It's like when you're half asleep and you think you hear your name called, but for them it's just constant.

Constant and very real.

Okay so those are the positive symptoms, the added stuff.

What about the negative ones?

These are functions that have been lost.

Things that should be there but aren't.

Like what specifically?

Emotional withdrawal.

Flat effect, meaning the person's face is like a mask, showing no emotion even if they feel it inside.

And hedonia.

Which is the inability to feel pleasure.

Right.

And also reduced speech, what we call elogia.

And the text makes a point that these negative symptoms are often much harder to treat than the positive ones.

Much harder.

And in many ways they are more devastating for the family.

Positive symptoms like hallucinations are scary, sure.

But negative symptoms, where the person you love just slowly disappears, stops talking, stops caring, that feels like losing the person entirely.

The text suggests these two categories might actually come from different neural disruptions because they respond so differently to medication.

So we know what it looks like.

The big question is, where does it come from?

Is it bad parenting?

Is it genes?

You know, the classic debate.

This brings us to the nature vs.

nurture debate.

And schizophrenia is one of the most studied disorders in this regard.

The text walks us through family studies, adoption studies, and of course, twin studies.

Let's look at the twin studies because that seems like the gold standard here.

Figure 16 .3 in the text breaks this down really clearly.

It does.

Because nature gives us perfect experiment.

Monozygotic twins.

Identical twins who share 100 % of their DNA.

If schizophrenia were purely genetic like eye color or Huntington's disease, then if one twin had it, the other twin would have it 100 % of the time.

The concordance rate would be 100%.

And what do the numbers actually say?

The concordance rate is about 50%.

50%.

Well, it's really high.

It's much higher than the general population, which is about 1%.

It is very high.

It proves genetics are a huge factor.

But the gap, that missing 50%, that's the most important takeaway.

Why is that?

It proves that genes are not destiny.

The genes load the gun, so to speak, but the environment pulls the trigger.

There has to be some external factor stress, a virus, trauma, that tips the scale.

So you can have the schizophrenia genes and live a perfectly healthy life.

Yes.

In fact, half the people with the exact genetic makeup of a schizophrenic person do develop the disorder.

And that is a massive source of hope, but also a huge mystery we need to solve.

What protects that healthy twin?

Okay.

So we have a genetic susceptibility.

Now let's open up the hood.

If I put a patient with schizophrenia into an MRI machine, what am I seeing?

Does their brain look physically different?

It does.

One of the most consistent findings going back decades is something called ventricular enlargement.

You can see this clearly in figure 16 .5.

The ventricles are those fluid -filled spaces deep in the brain, right?

They look like little butterflies in the center of the brain scan.

Yes, exactly.

They're filled with cerebrospinal fluid.

They act as a cushion for the brain.

In many patients with schizophrenia, these spaces are significantly larger than in healthy people.

But the skull isn't getting any bigger, so if the empty space is getting bigger...

Then the brain tissue itself must be shrinking.

That's the direct implication.

The neural matter is either atrophying or perhaps it never developed properly in the first place, leaving these large empty caverns.

And there is a specific gene mentioned here, DISC1.

Researchers created transgenic mice with a mutated version of this gene to see what would happen.

This is a great example of how we use animal models to test these hypotheses.

They took a mouse, they gave it the mutated DISC1 gene, which is a gene known to be abnormal in some human families with a history of schizophrenia, and they just watched its brain develop.

And what did they find?

And sure enough, the mice with the mutant gene developed enlarged lateral ventricles.

It's a direct link.

This one gene mutation leads to this specific structural change we see in humans.

But it's not just the holes in the brain that are the problem.

It's the wiring itself, right?

The text talks about cellular disarray in the hippocampus.

This is fascinating and disturbing.

The hippocampus is crucial for memory and navigating the world.

In a healthy brain, the pyramidal cells, the main neurons there, are lined up neatly.

Think of them like a regiment of soldiers standing in formation, all facing north.

Very organized.

Very organized.

And in a brain with schizophrenia.

It's chaos.

The soldiers are breaking ranks.

Some are facing east, some west, some are bumping into each other.

It's cellular disarray.

It's a mess.

And the expert opinion is that this happens early, right?

This isn't damage from living a hard life or from drug use.

Right.

This disorganization looks like it happens during neuronal migration.

That's when the brain is forming in the womb.

The cells are trying to move to their correct positions and they just, they get lost.

The wiring is faulty before the person is even born.

So you have these structural issues deep in the brain, in the limbic system.

But what about the frontal cortex?

We talk about the frontal lobe a lot.

It's the CEO of the brain.

Planning, logic, inhibition.

In schizophrenia, we see something called hypofrontality.

That's a fancy way of saying the frontal lobes are underactive.

The CEO is asleep at his desk.

They prove this with a really clever test called the Wisconsin card sorting task.

How does that work?

Can you walk us through it?

It's deceptively simple.

I give you a deck of cards with different shapes, a triangle, circle, squares, and different colors, and I just ask you to sort them.

Maybe you start sorting by color.

All the reds here, all the blues there.

I say, correct, you keep going.

But then, without telling you, I change the rule.

Now, color doesn't matter.

It's about shape.

So I put a red card on the red pile and you say, wrong.

Exactly.

Now, a healthy brain immediately kicks into high gear.

The frontal lobe lights up on a Pete scan.

You think, okay, the rule changed.

Let me try shape.

You adapt.

And a person with schizophrenia?

They get stuck.

They keep sorting by color over and over again, even though they keep feedback.

They can't shift their strategy.

And on the brain scan, their frontal lobes barely flicker.

There is no surge of activity to handle the problem.

That explains so much of the rigid thinking and the inability to function in daily life when things don't go according to plan.

It does.

Okay, so we have the structure, the hardware is glitched.

Now let's talk chemistry, the software.

This is where the drugs come in and where the big hypotheses live.

The dominant theory for decades was the dopamine hypothesis.

And like many things in science, it started with an accidental observation involving street drugs,

specifically amphetamines.

Speed.

Speed.

What happens if you take too much speed?

You develop amphetamine psychosis, you get paranoid, you get delusions, you start hearing things.

The symptoms look almost exactly like the positive symptoms of schizophrenia.

And biologically, we know amphetamine causes a massive flood of dopamine in the brain.

So the logic was simple.

Too much dopamine makes you act psychotic.

Therefore, schizophrenia must be caused by too much dopamine.

It's compelling syllogism.

And it was supported by the discovery of chlorpromazine, the first real anti -psychotic drug.

It worked by blocking dopamine receptors, specifically the D2 receptor.

It acted like a dam, stopping the flood of dopamine.

And the positive symptoms went away.

For many patients, yes.

But there's a catch, isn't there?

There's always a catch in neuroscience.

The catch is that dopamine blockers are messy.

They stop the voices, yes.

But they don't really fix the negative symptoms, the emotional flatness, the withdrawal.

And even worse, some patients don't respond to them at all.

If it was just dopamine, everyone should get better.

Exactly.

Which brings us to the challenger, the glutamate hypothesis.

This came from observing a different drug,

PCP, vancycladine.

Also known as angel dust.

A very different kind of high than speed.

Very.

PCP causes a dissociative state.

And crucially, it causes both positive and negative symptoms.

People in PCP get auditory hallucinations, but they also get the emotional withdrawal and the cognitive problems we see in schizophrenia.

So it mimics the full spectrum of the disease better than amphetamine does.

And what does PCP do to the brain?

It blocks NMDA receptors.

These are the receptors for glutamate, which is the brain's main excitatory neurotransmitter.

So if blocking glutamate mimics the disease.

Then the disease itself might be caused by an underactivation of glutamate.

The text has this great diagram, figure 16 .14.

It's a channel that lets calcium into the cell.

PCP sits right in the middle of the tube, like a cork in a bottle, just blocking the flow.

So the calcium can't get in, the neuron doesn't fire correctly, and you get psychosis.

Exactly.

It suggests that schizophrenia is a complex interplay of dopamine and glutamate.

Maybe the glutamate system is the primary problem, and the dopamine system goes haywire as a consequence.

It's fascinating that we've learned so much about mental illness, essentially, by reverse engineering what street drugs do to the brain.

It is a bit dark, isn't it?

We look at what breaks the brain to understand how it works normally.

Before we move on, we have to acknowledge the dark history of treatment.

The text mentions lobotomy.

Yes.

The story of Howard Dulley is mentioned.

In the mid -20th century, before we had these drugs, doctors were desperate.

They would surgically use an instrument that was basically an ice pick.

It sounds barbaric to us now.

And they would detach the frontal lobes from the rest of the brain.

It does sound barbaric, but we have to understand the context.

Asylums were overflowing.

There was no cure.

This was a Hail Mary.

But the results were often tragic.

Patients were left apathetic, childlike, essentially stripped of their personality.

It's a grim reminder of why understanding the actual biology is so important, so we don't have to resort to blunt force trauma to treat these conditions.

Absolutely.

The goal is precise chemical intervention, not surgical destruction.

And before we leave schizophrenia, we should mention the environmental factors one last time.

There is a strange finding about birth months.

Oh, right.

The spring babies.

Yes.

People born in early spring are slightly more likely to develop schizophrenia.

The theory is that their mothers might have been exposed to the flu during the second trimester of pregnancy, which would be in the winter months.

So a viral infection in the mother affects the fetal brain development.

Exactly.

It could disrupt that cell migration we talked about earlier.

It's another piece of evidence that this is a developmental disorder, with roots long before the first symptoms ever appear.

Let's pivot to a disorder that shares some genetic DNA with schizophrenia, but manifests very differently.

Bipolar disorder.

Right.

Formally called manic depressive illness, and is characterized by these extreme, distinct swings.

You have lows of depression, but they alternate with periods of mania.

What does mania actually look like?

Is it just being really happy?

It's way past happy.

It's sustained overactivity, talkativeness, grandiosity, just infinite energy.

People in a manic state might stay up for four days straight writing a novel, or spend their entire life savings on a business idea at 3 a .m.

They feel invincible.

Totally invincible.

And the text says there are similarities in the brain structure to schizophrenia.

Yes.

Those enlarged ventricles show up again.

And scarily, the more manic episodes a person has, the larger the ventricles seem to become.

So the disease process itself is damaging the brain over time.

It's neuro -progressive.

It is.

The treatment for this has a legendary origin story.

Lithium.

Oh, one of the great accidents of medicine.

In the 1940s, a researcher named John Cade

was, well, he was injecting guinea pigs with urine from manic patients.

Don't ask why.

Early science was weird.

Laughs.

Okay.

And he mixed the urine with lithium just to make it soluble.

He was using lithium as a chemical delivery truck.

Nothing more.

But the guinea pigs didn't get agitated like he expected.

No.

They became incredibly calm.

He realized the lithium itself was the psychoactive agent.

To this day, lithium is the gold standard for stabilizing bipolar mood swings.

Do we know how a simple element like lithium works?

I mean, it's just an element on the periodic table.

Honestly.

It's still a bit of a mystery.

We know it interacts with the circadian clock, those sleep -wake cycles that get so disrupted and bipolar.

And we know it boosts BDNF brain -derived neurotrophic factor.

Which sounds like fertilizer for brain cells.

That's a perfect analogy.

It helps neurons survive and grow.

In fact, lithium treatment has been reported to actually increase gray matter volume in patients.

It can reverse some of that brain shrinkage we see.

Now, here's where it gets really interesting for me.

The text brings up the creativity connection.

We've all heard the stereotype of the tortured artist.

Van Gogh, Hemingway, Sylvia Plath.

Is there real data on this or is it just romanticizing illness?

There is real data.

A massive study of 100 ,000 people in Iceland and Sweden looked at genetic risk scores for schizophrenia and bipolar disorder.

So not just people who had the disease, but people who carry the genes for it.

Exactly.

And they found that people with high genetic risk scores were significantly more likely to be in creative professions.

Actors, dancers, musicians, visual artists, writers.

That's profound.

It suggests that the same genetic variants that can cause these devastating disorders might also confer some advantage in associative thinking outside the box.

It raises a really difficult philosophical question.

If we could cure these genetics entirely, if we could edit out the risk of bipolar,

would we also be editing out the next Van Gogh?

It's a trade -off inherent in our biology.

We have to be very careful about what we define as broken.

But for the people suffering through the severe lows,

the need for treatment is absolutely undeniable.

That's a good transition.

Let's move to the most common mood disorder, depression.

The brain in the darkness, as the text puts it.

And depression is so much more than just sadness.

Sadness is a normal reaction to loss.

Depression is a whole body physiological state.

Unhappy mood, yes, but also loss of energy, difficulty concentrating, changes in appetite, changes in sleep.

And the brain scans show a very specific pattern.

It's not just everything is low.

No, not at all.

It's a specific imbalance.

Peony scans, which you can see in figure 16 .21, show increased blood flow in the amygdala.

The fear center.

Right.

So even if the person looks lethargic on the couch, their fear center is screaming.

But simultaneously, there is decreased blood flow in the parietal and posterior temporal cortex, which are involved in attention.

So high fear, low attention.

It's a recipe for misery.

You are hyper aware of your own internal negative state, but you're unable to focus on the external world to distract yourself.

You are trapped in your own head.

Let's talk about the chemistry.

We all know about serotonin.

SSRIs like Prozac are household names.

The monoamine hypothesis says depression is caused by low serotonin.

Case closed, right?

Not quite.

This is what we call the chemical paradox.

I love a good paradox.

Lay it on me.

Okay.

SSRIs work by blocking the reuptake of serotonin.

This happens immediately.

Within hours of taking the pill, your synaptic serotonin levels spike.

The chemical problem is, in theory, fixed.

Okay.

But patients don't feel better for weeks, sometimes a month or even six weeks.

So if the chemical is fixed in an hour, why does the mood take a month to fix?

That is the million dollar question.

It implies that low serotonin isn't the direct cause of the mood.

Instead, the serotonin spike triggers a slow downstream process.

The leading theory now is that it triggers neurogenesis, the growth of new neurons, especially in the hippocampus.

So the drug doesn't make you happy.

The drug tells your brain to start rebuilding itself, and that makes you happy.

Exactly.

It's about plasticity, not just juice in the tank.

The brain needs time to literally rewire.

The text also brings up the HPA axis, the stress system.

This feels relevant because stress and depression seem so tightly linked.

They are.

The HPA axis is the hypothalamic pituitary adrenal axis.

In a healthy person, stress triggers cortisol release.

Cortisol helps you handle the stress.

It mobilizes energy.

Then the brain detects that cortisol and says, okay, we have enough.

Shut it down.

It's a negative feedback loop.

Like a thermostat turning off the heat when the room gets warm.

A perfect analogy.

But in depression, that thermostat is broken.

Depressed patients have chronically elevated cortisol levels.

They have a test for this, the dexamethasone suppression test.

They give a patient a synthetic hormone that should trick the brain into shutting down cortisol production.

And in depressed patients.

It fails.

The brain just keeps pumping out stress hormones.

Their system is stuck in the on position.

That sounds absolutely exhausting.

Being stuck in fight or flight mode while also feeling unable to move.

It is physically damaging.

High cortisol is toxic to neurons over time.

It actually kills brain cells.

This is likely why we see shrinkage in the hippocampus of depressed patients.

It's a vicious cycle.

And it messes with sleep too.

I found the section on sleep architecture really specific and interesting.

It is.

Sleep is divided into stages.

Stage three is your deep, restorative, slow wave sleep.

Depressed patients basically lose stage three.

Their sleep is very light and fragmented.

They don't get that deep restoration.

And what about dreaming?

REM sleep.

They enter REM sleep, dream sleep, much too early in the night.

Their biological rhythms are completely out of sync.

It's like their brain is running a marathon in their sleep, which helps explain the constant fatigue they feel during the day.

The text also touches on gender.

Depression is more common in women.

Is that hormonal?

There is strong evidence for it.

Postpartum depression is the clearest example.

It happens right when there's a massive hormonal crash after childbirth.

But then there's SAD seasonal affective disorder.

The winter blues.

The text is actually a bit skeptical on SAD, isn't it?

Which surprised me.

It is.

We all intuitively feel like dark days make us sad.

But the text notes that large -scale studies have struggled to find a consistent link between day length and depression rates across different latitudes.

It might be more complex than just lack of sun.

So how do we break the cycle?

We have pills, but what else?

There's cognitive behavioral therapy, or CBT.

The text describes the treadmill of depression in figure 16 .23.

Negative thoughts lead to low mood, which leads to reduced behavior, which then just confirms the negative thoughts.

Exactly.

It's a loop.

CBT tries to jam a stick in that wheel, even just changing the behavior.

Getting the person to exercise, for example, can break the cycle.

And we know exercise boosts BDNF, just like the drugs do.

And for the really severe cases, the ones where drugs and therapy fail.

We have ECT,

electroconvulsive therapy.

Shock therapy.

That sounds medieval.

People picture one flu over the cuckoo's nest.

It has a terrible reputation from movies.

But biologically, it's a fascinating reset button.

For intractable depression, it can be a lifesaver.

It induces a controlled seizure.

We still don't know exactly why it works, but it seems to reset the synaptic sensitivity across the brain.

And there's also deep brain stimulation, DBS.

Yes, surgically implanting an electrode to stimulate the cingulate cortex.

It's like a pacemaker for the mood circuits of the brain.

It's very cutting edge, but it shows how far we've come from just talking about our feelings.

Before we leave depression, I want to ask about the rats again.

How do you study depression in a rat?

You can't ask it if it feels hopeless.

You look for learned helplessness.

This is a famous, if kind of sad experiment.

If you expose an animal to an unpleasant shock that it cannot escape, eventually it just stops trying.

It just curls up and takes it.

That's heartbreaking.

It is.

But here is the kicker.

If you then put that same rat in a box where it can escape, where there is an open door, you won't even try to move.

It has learned that its actions don't matter.

It has learned helplessness.

And that is a powerful model for the cognitive state of human depression.

It's not that you can't change your life.

It's that you believe you can't.

Precisely.

Okay, let's move on to anxiety and PTSD.

These are related, but they are different.

Anxiety is a spectrum.

You have phobias, fear of spiders,

panic disorder, sudden overwhelming terror, generalized anxiety, just constantly worrying about everything.

And the big drugs here are bendode azepines.

Ivalium, Xanax.

Right.

And how do they work?

They work on the GABA receptor.

We need to define GABA.

GABA is the brain's main inhibitory transmitter.

It's the chill -out signal, the brake pedal.

Okay, the brake pedal.

So bendode azepines bind to the GABA receptor, and they act as a force multiplier.

They help the GABA receptor open its chloride channels wider.

Chloride channels, we're back to ions.

We are.

Think of chloride ions as a fire extinguisher.

When they flow into a neuron, they make the inside more negative, they hyperpolarize it.

This makes it much harder for the neuron to fire.

So the benzos help GABA hold the fire extinguisher trigger down, dousing the anxiety.

That's a great visual.

It inhibits the whole system.

But then there is PTSD, post -traumatic stress disorder.

This isn't just being anxious.

No, this is a specific failure of memory extinction.

Extinction.

What does that mean?

In a healthy brain, if you have a scary experience, you eventually learn that the danger is over.

The fear extinguishes.

In PTSD, that memory, that fear conditioning, it never fades.

The amygdala becomes hyper -responsive to anything that reminds them of the trauma.

So a car backfiring sounds like a gunshot.

And the brain reacts as if it is a gunshot, with the full physiological response.

There's a fascinating chicken or egg question in the text regarding the hippocampus and PTSD.

This is one of my favorite parts of the chapter, because it shows the power of twin studies again.

We know that people with PTSD tend to have a smaller hippocampus.

And the hippocampus is involved in memory and context.

Right.

So the question was,

did the trauma of war cause the hippocampus to shrink?

Or did having a small hippocampus to begin with make the person more vulnerable to getting PTSD?

How could they possibly solve that?

They found combat veterans with PTSD, and then they looked at their identical twins who did not go to war.

So twin A saw combat and has PTSD.

Twin B stayed home and is fine.

Exactly.

They scanned twin B's brain.

And guess what?

Don't tell me.

Twin B also had a small hippocampus.

Wow.

So the small hippocampus came first.

It's a pre -existing condition.

Exactly.

It's an inherited risk factor.

If you are born with a smaller hippocampus, and you are exposed to severe trauma, you are biologically less equipped to process that memory contextually.

You're more likely to develop PTSD.

That is huge for screening.

We could theoretically identify soldiers who are at higher risk before they ever see combat.

That is the promise of this research.

Prevention based on biology.

Let's get to OCD, Obsessive Compulsive Disorder.

This is characterized by obsessions, which are intrusive, unwanted thoughts and compulsions, which are the repetitive acts performed to quiet those thoughts.

If I don't wash my hands 10 times, my family will die.

It's described as a loop in the brain,

a stuck circuit.

It is literally a circuit loop.

The text describes it as orbitofrontal cortex to the cingulate, to the caudate nucleus, to the thalamus, and then right back again.

It's like a song stuck on repeat at maximum volume.

The brain cannot shift gears out of the thought.

And the text mentions a surprising trigger for this in children.

PANDAS.

Not the bear.

No, not the bear.

PANDA stands for Pediatric Autoimmune Neuropsychiatric Disorders associated with streptococcal infections.

Strep throat.

Strep throat.

The theory is that the child gets strep.

The immune system makes antibodies to fight the bacteria, but those antibodies get confused.

They cross the blood -brain barrier and they attack the basal ganglia in the brain.

So it's friendly fire.

Exactly.

And suddenly, almost overnight, the child develops severe OCD or ticks.

That is terrifying but also hopeful because it means it's an immune issue.

You could treat it with antibiotics or immune therapy rather than just psychiatric drugs.

It just highlights how interconnected the body and brain really are.

The brain isn't an island, it's part of the whole system.

And related to OCD is Tourette's Syndrome.

Yes.

They are often comorbid, they occur together.

Tourette's involves motor and vocal ticks and it's linked to the basal ganglia too, specifically a greater density of dopamine D2 receptors in the caudate nucleus.

So again, dopamine is a major player.

It is.

Researchers view OCD in Tourette's as related disorders of the basal ganglia, the part of the brain that controls the initiation of movement and action.

It's an inability to inhibit unwanted actions or thoughts.

We're coming into the homestretch here.

The final section is about the cutting edge, eye tracking.

This brings us full circle to the Argyle Robertson pupil, doesn't it?

We're back to the eyes.

We're always looking for endophenotypes, these hidden biological markers that can warn us of risk before symptoms start.

And the eyes have it.

It seems so.

People with schizophrenia have trouble with smooth pursuit eye movements.

If I put a dot on a screen and move it slowly from left to right, you can track it smoothly.

Your eyes just glide.

And a person with schizophrenia.

Their eyes jerk.

They stumble.

It's called saccadic intrusion.

They can't lock on and glide smoothly.

Their eyes keep making these little corrective jumps.

But is it accurate enough to be a real test?

A study mentioned in the text used a mathematical model of this eye tracking data.

It was able to discriminate schizophrenia cases from controls with a 98 % accuracy.

98%.

That's better than most medical tests for physical diseases.

It's incredible.

Imagine a future where a teenager goes for a checkup, looks into a scanner for two minutes, and the doctor says, you have a tracking error that indicates a high risk.

Let's start stress reduction therapies and cognitive training now.

Before the first voice is ever heard.

Before she is leaving the building.

Exactly.

That is the dream.

To move from crisis management to prevention.

That is the promise of biological psychiatry.

Okay, let's wrap this up.

We've covered a massive amount of ground.

Syphilis, large ventricles, dopamine, lithium, cortisol loops, and eye tracking.

It is a dense chapter.

But the overarching theme is undeniable.

Behavioral disorders are biological.

They are disruptions in the wiring, the chemistry, and the structure of the most complex machine in the known universe.

And understanding that, I mean, it helps strip away the stigma, doesn't it?

Eleanor wasn't possessed.

She wasn't weak.

She had a cellular disarray in her hippocampus and a disruption in her dopamine and glutamate systems.

It's an organ failure, just like a heart attack or kidney disease.

Precisely.

And by understanding the mechanism, we can find the fix.

Just like antibiotics fixed paralytic dementia,

we hope that understanding the genome and the connectome will eventually fix schizophrenia and depression.

But I want to leave the listener with that provocative thought you mentioned earlier, that creativity connection.

Right.

The fact that the same genes that tilt the brain toward bipolar or schizophrenia also seem to tilt it toward creativity is a really profound realization.

It suggests that the human spectrum of neurodiversity is there for a reason.

We want to cure the suffering.

Absolutely.

Nobody should have to live with terrifying voices or crippling depression.

Of course not.

But in our quest to normalize the brain, we have to be careful to understand what we might be editing out of the human experience.

If we eliminate the extremes, do we lose the genius that so often lives at the edges?

A profound thought to end on.

You want to see the visuals we talked about, the cellular disarray, the brain scans, the ventricles.

I highly recommend looking at figures 16 .5 and 16 .8 in the chapter.

Seeing the physical change makes it so real.

Absolutely.

It drives the point home.

Thank you for listening to this deep dive.

A big thanks from the last minute lecture team.

Stay curious, stay informed, and we'll catch you on the next one.