Chapter 16: Neuropsychiatry and Neuropsychology

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Picture this.

It's the late 20th century and a highly respected psychiatric journal receives this paper proposing a link between hemisphere laterality and schizophrenia.

Right, which gets summarily rejected.

An anonymous eminent academic reviewer sends it back basically calling the entire concept an outdated and futile exercise.

Yeah, essentially telling the author, you know, don't bother looking for physical brain abnormalities and schizophrenia.

It's a waste of time.

Exactly.

But here is the kicker.

A comedy writer, P .G.

Woodhouse, had actually already published a comic novel just a bit earlier in 1969.

It was called A Pelican at Blanding's.

I love this story.

In that novel, a character literally jokes that a girl's bizarre behavior must be because her two hemispheres and her corpus callosum had gone wrong, rendering her, as he put it, potty.

A comedy writer nailed the neurobiology before the top scientific reviewers would even like entertain the idea.

It's incredible.

It really is.

Welcome to a very special Last Minute Lecture deep dive.

If you, the listener, have got a major exam coming up on chapter 16 of Introduction to Neuropsychology, second edition, you are exactly in the right place.

We are essentially stepping in as your personal one -on -one tutors today.

Exactly.

Our mission is to help you completely master this chapter, focusing heavily on neuropsychiatry and neuropsychology, and we're going to do it in the exact order it appears in your textbook.

So you are fully prepped.

What's fascinating here is that the irony of that Woodhouse story perfectly captures the tension you really need to understand for this chapter.

The tension between neurology and psychiatry, right?

Exactly.

For a very long time, those two fields operated in complete silos.

They only really focused on what we call organic psychiatry.

Which means conditions with visible,

obvious brain damage, like you can see it on a scan.

Right.

But slowly, the field realized they needed to look at functional disorders, too.

Things like schizophrenia or severe depression, where the physical brain pathology wasn't

immediately obvious to the naked eye.

And bridging those two worlds is what birthed the modern specialty of neuropsychiatry.

Precisely.

Okay, let's unpack this.

Because to really grasp that bridge, we have to start with the physical roots of mental states.

First up in the chapter is organic psychiatry.

Right.

So we know that abnormal mental states follow brain damage.

But the type of damage makes a massive difference.

So we're talking about focal lesions versus diffuse damage.

Exactly.

You have focal lesions, which are these pinpoint, highly localized areas of damage.

Yeah.

And then you have diffuse brain diseases or general trauma that just wash over the entire brain system.

No, I feel like it's really tempting for a student to assume that any brain damage automatically guarantees severe psychiatric fallout.

Oh, uses a massive 1960 study by Hillbomb to show how nuanced this actually is.

Right.

The one with the war veterans.

Yeah.

3 ,500 war veterans with brain injuries.

You would expect catastrophic numbers from a sample size like that, considering it's brain trauma from a war.

You think so.

Yeah.

But lasting cognitive impairment was only present in 2 % of those veterans.

Wow.

Just 2%.

Yeah.

Character changes were at 18%.

Psychosis at 8%.

And severe neurosis at 11%.

So terrible, obviously, but not a guaranteed 100 % psychiatric breakdown across the board.

Right.

But then you compare that to patients with brain tumors, where the text notes mental changes happen in a staggering 50 to 80 % of cases.

Oh, wow.

So the specific nature of the organic trauma heavily dictates the psychiatric outcome.

Exactly.

But when organic nervous disease does cause issues, a pretty predictable cluster of general symptoms emerges.

I'd imagine if the physical hardware is damaged, the foundational operating systems of the body just go offline first.

That is a very solid way to frame it for the exam.

So you see disrupted sleep, altered states of consciousness, memory slipping, patients tire easily.

And the text also mentions perseveration.

Yes.

Perseveration is basically getting stuck repeating the exact same thoughts or actions like a skipping record,

along with emotional volatility and a complete lack of inhibition.

And for general trauma, the chapter specifically highlights post -concussion syndrome or post -traumatic neurosis.

Right.

Which brings on severe headaches, giddiness, fatigue, anxiety, and depression.

Plus, there's this one highly specific symptom you should definitely circle in your notes if you're listening.

A particular concern for their head.

Which makes total sense, right?

Completely logical.

If your head took a major hit, you'd be hyper aware of Definitely.

So moving along that spectrum of organic conditions, the chapter then dives into epilepsy.

Right.

And with chronic seizures constantly disrupting the brain's electrical activity, it seems like severe mental health issues would just be a given.

It does seem that way.

However, epileptics in general only have about a 5 % rate of serious psychiatric diagnosis.

Which is higher than the 1 % in the general public, sure.

But it's remarkably low given the sheer physical disruption of a full seizure.

It is.

But there is a major exception you need to know.

Temporal lobe epilepsy.

Ah, right.

That's the one that changes the game.

It really does.

That specific variant is disproportionately linked to mental health admissions.

The abnormal behavior can trigger right after a seizure, or it can settle into a chronic psychotic state.

And that state closely mimics paranoid schizophrenia, right?

Exactly.

The literature even describes an epileptic personality characterized by stubbornness, egocentricity, and a lack of spontaneity.

But wait, let's think about this critically for the exam.

If someone has a chronic, highly stigmatized condition like severe epilepsy,

are those personality treats like the stubbornness actually caused by the temporal lobe physically misfiring?

That's the big question.

Or, you know, are we just looking at the immense secondary psychological stress of living with a severe handicap in society?

The text actually leans heavily toward the latter.

Those older clinical descriptions of the epileptic personality were largely based on institutionalized patients.

Right.

Not people managing the condition out in the community with normal support systems.

Exactly.

It is crucial to separate primary cerebral effects from secondary psychological reactions to the illness.

Which brings us to a condition where the primary cerebral effect is undeniable, dementia.

Yes.

Here we're talking about a progressive physical loss of cortical tissue.

A total system breakdown.

Basically, as the cortex dissolves, memory, motor performance, and eventually basic vital processes just progressively deteriorate.

So that's the diffuse brain damage.

It causes that total global collapse.

But what happens when the damage isn't everywhere?

You mean when it's focal?

Right.

What if it is pinpointed to one tiny specific spot in the brain?

That is where reality shatters in incredibly bizarre, hyper -specific ways.

The chapter outlines several rare neuropsychiatric syndromes.

Though it is worth noting their apparent rarity might just be because patients are terrified to report them.

That's a very good point.

Imagine experiencing something completely impossible, but being too afraid of being labeled mad to actually tell your doctor.

Yeah.

So let's look at Capgras syndrome.

This is absolute conviction that imposters have replaced your loved ones.

It's terrifying.

Up to half of these cases are linked directly to neurological disease,

specifically right hemisphere abnormalities.

The author shares this heartbreaking case of a teacher who, after a car accident, believed her family and her school colleagues were all identical imposters.

She couldn't even return to work because she thought her students were fakes.

To understand the mechanics of why this happens, we really have to look at how the brain processes faces.

Right.

You essentially have two main tracks running simultaneously.

The visual recognition track and the emotional response track.

Exactly.

The visual track identifies the geometry and features of the face.

The emotional track gives you that warm, familiar feeling when you see someone you love.

But in Capgras, the visual track still works perfectly, right?

It does.

The patient knows the person standing there looks exactly like their mother, but the physical lesion has severed the emotional track.

So they feel zero emotional warmth.

Zero.

And the brain absolutely panics trying to solve this terrifying paradox.

Right.

So the only logical conclusion the brain can reach to explain the lack of feeling is, well, this woman must be a perfect physical imposter.

It's just the brain desperately trying to make sense of broken sensory input.

You see a similar mechanical breakdown in Cotard syndrome, too?

Or the syndrome of nihilism?

Oh, Cotard is fascinating.

The patient genuinely believes they are dead,

that their body is a literal corpse or that they are missing their internal organs.

Wow.

And this is also strongly linked to right hemisphere lesions and face processing impairments, right?

Yes.

If the profound emotional disconnection we saw in Capgras is applied to your own reflection in the mirror or your own internal bodily sensations.

The brain just concludes, I must not exist.

Exactly.

I feel nothing.

Therefore I am dead.

So grim.

Closely related to that is Fregoli syndrome, which swings in more of a paranoid direction.

Right.

The patient believes a single specific persecutor is following them, but constantly disguising themselves as everyday people.

So the mail carrier, the barista, the neighbor, the patient thinks they are all the exact same sinister person wearing different masks.

It's exhausting.

And the text also highlights how frontal brain injuries can take mild pre -existing traits and turn them into severe obsessive disorder.

Oh, right.

OCD.

Like a patient who used to just prefer a tidy desk might suddenly be completely unable to sleep without checking the gas stove 20 times.

Yes.

The inhibition just disappears.

The author actually includes this incredibly vivid case study of how this manifests as intrusive thoughts.

The cheese grater case.

Yes.

The author was sitting with a patient who had absolutely no history of violence.

But as they talked, the patient's injured brain generated a relentless, grotesque image.

He kept picturing removing the skin from the author's arm with a cheese grater.

The patient was so profoundly distressed by his own brain, forcing these horrifying perceptions into his everyday consciousness that he isolated himself completely.

It just proves how a physical injury can completely hijack the mind's internal theater.

Now conditions like cap grass after a car crash or violent OCD after a frontal lobe injury, those show a clear cause and effect on an x -ray.

Right.

We can see the damage.

But what about severe mental illnesses where the brain scans look seemingly normal?

Okay.

We are now entering the territory of functional states.

Right.

If you were trying to keep the terminology straight for the exam, remember the clear dividing line between neuroses and psychoses.

Let's define those for the listener.

Neuroses sit on the less severe end of the spectrum.

Things like anxiety or depression.

The key here is that the patient maintains contact with reality and has insight into their condition.

Meaning they know something is wrong with how they feel.

Exactly.

Psychoses are the major functional disorders.

Schizophrenia or bipolar affective illness, which is also called manic depressive illness.

And this is where you see a profound loss of reality, hallucinations, bizarre behavior.

And crucially, a complete lack of insight.

The patient doesn't know their reality is broken.

But hunting for the physical brain basis of these functional states is, well, it's a methodological nightmare.

If we connect this to the bigger picture,

psychiatric diagnostic labels are just notoriously slippery.

The term schizophrenia gets used very loosely to cover a massively diverse range of symptoms.

Plus these patients are almost always on heavy, powerful, psychotropic drugs that fundamentally alter their central nervous system.

Which completely muddies the waters of any study.

Yeah.

And frankly, the text warns that researchers have a bad habit of taking this incredibly messy clinical data and squeezing it into molds formed by their own pre -existing expectations.

They absolutely do.

Despite that messy data, the primary quest over the last few decades has been to prove that functional psychoses are actually caused by an imbalance between the left and right hemispheres.

The hunt for

Exactly.

Early on, researchers looked for behavioral clues.

Some studies claim that conversion symptoms, like a hysterical psychogenic paralysis, happen more often on the left side of the body.

And since the right hemisphere controls the left side of the body and the right hemisphere is supposedly the more emotional side, they thought they found the link.

Right.

But the text quickly shoots that down, citing a 1981 study by Hall.

What did Hall find?

When Hall looked at a massive sample of pain clinic patients, there was absolutely no left -sided asymmetry for psychogenic pain.

So behavioral observation simply wasn't cutting it.

They had to go into the brain itself.

Which brings up the water technique.

The text highlights a famous 1971 study by Holmes and Panhoysin.

Oh, this is wild.

They took patients with severe depression and injected sodium, a metal, to essentially put one hemisphere of the brain to sleep at a time.

Literally half the brain just takes a nap.

When they injected the left side, putting it to sleep, the patients actually showed an improved elevated mood.

Their conclusion was that normal mood regulation heavily depends on the functional dominance of the left hemisphere.

We also see clues in the brain's electricity, right?

Like with ECT.

Yes.

Electroconvulsive therapy administered to depressed patients actually improves their performance on right hemisphere cognitive tests.

And EEG readings, which measure electrical activity, show abnormalities in the left temporal lobe for patients with formal thought disorder.

There is a vital concept here for your notes regarding schizophrenia.

The 2007 Higashima study.

Definitely write this one down.

It found that acute psychotic symptoms are linked to an EEG coherence disconnection between the frontal and temporal lobes of the left hemisphere.

Think of EEG coherence like a massive symphony orchestra.

The frontal lobe and the temporal lobe need to be playing the exact same song in perfect time with each other.

Right, a unified output.

A coherence disconnection means the string section and the brass section suddenly lose the conductor.

They fall completely out of sync and that chaotic electrical noise manifests as acute psychosis.

That's a great analogy.

As imaging technology improved, PE scans and MRIs allowed us to see the structural asymmetry even more clearly.

Here's where it gets really interesting.

A 2006 PE study by Stephane looked at auditory hallucinations, you know, people hearing voices.

Yeah.

It found abnormal laterality in the supplementary motor area.

The mechanism here is fascinating.

The brain is generating its own internal speech, right?

Yes, but because of this physical asymmetry, it fails to tag that speech as self -generated.

So the patient actually perceives their own thoughts as an external alien voice.

It's incredible MRI studies back this up, too.

Chaplesque found greater structural asymmetry in the Sylvian fissure in schizophrenic patients.

And Brambilla found an abnormally reduced and inverse cerebral blood volume, which might actually be the mechanism driving the brain atrophy we see in schizophrenia.

We even see this verified in psychopharmacology.

Drugs like piracetam, which improve the transfer of information back and forth between the hemispheres, actually improve memory in schizophrenic patients.

And chlorpromazine, a major tranquilizer, decreases lateral asymmetry during auditory tasks.

Alongside the imaging and the drug, psychologists use behavioral cognitive tasks to hunt for broken communication.

Like the divided visual field technique, this flashes images to only one side of the brain to see if the two halves are talking to each other.

Another one is dichotic listening, where different sounds are piped into each ear simultaneously.

The results across the literature are notoriously mixed for this one, but the 2005 Mitchell and Crow study is a standout.

What did they find?

They suggest the severe social interaction problems in schizophrenia might stem from the right hemisphere.

We always think of the left brain as the language center, right?

Sure, for vocab and grammar.

But the right hemisphere handles the intent of language.

Yeah.

The tone, the subtext, the social cues.

If those right hemisphere functions aren't properly segregated, the ability to navigate social communication just completely collapses.

And lastly, eye movements.

Studies consistently show schizophrenic patients have increased rightward conjugate lateral eye movements.

Yeah, because looking to the right is linked to left hemisphere activation.

Researchers interpret this as a sign of an abnormal process firing off in the dominant left hemisphere.

So we have a mountain of conflicting clues.

Left hemisphere overactivation, right hemisphere underactivation, disconnected lobes, faulty blood flow.

It's a lot.

To organize this chaos for the exam, the chapter provides four major theoretical models attempting to explain lateral asymmetry in functional psychiatry.

Model number one is Galen's psychodynamic model.

This one attempts to bridge Freud with neurobiology.

Interesting.

It links the right hemisphere to the Fordian primary process and the unconscious.

The theory is that if the hemisphere gets disconnected from the logical speaking left hemisphere, it causes repression and psychiatric symptoms.

Though the text is quick to note, this isn't very popular in modern, highly biological psychiatry.

Not at all.

Model number two is much more straightforward.

Floor Henry's specific lateralized dysfunction.

Right.

Floor Henry argues that abnormalities on the dominant side, usually the left result in schizophrenia.

In abnormalities on the Model number three is Diamond's disconnection syndrome.

This model argues that the individual hemispheres themselves might actually be perfectly fine, but the bridge between them, the corpus collusum is broken.

It's like having two perfectly functioning supercomputers, but the fiber optic cable connecting them has been severed.

Right.

Psychiatric symptoms are simply the result of that failed information transfer across the brain.

Finally, model number four is Davidson's valence model.

This posits that the anterior parts of the brain and the amygdala are divided by emotion rather than just logic and creativity.

So the left side handles positive emotions and approach behavior.

The right side handles negative emotions and withdrawal behavior.

Think of it like the pedals in a car.

The left hemisphere is the gas pedal moving you toward positive stimuli.

The right hemisphere is the brake pedal pulling you away from negative stimuli.

So damage to one frontal lobe throws off that entire emotional balance.

Exactly.

If your left side is damaged, you lose your gas pedal, leaving you stuck with only the brake, which looks exactly like severe clinical depression.

This is supported by the WADA studies we discussed earlier and data from stroke patients.

But testing it in clinical populations is incredibly complicated by a phenomenon called alexithymia.

Right.

Alexithymia is a patient's faulty perception of their own emotions.

It is almost impossible to accurately test someone's internal move state if their brain injury has fundamentally destroyed their ability to accurately feel or describe their own emotions in the first place.

Exactly.

Which brings us to the most critical point for your exam.

You have to be able to critically evaluate these models, and that means understanding the post hoc trap.

Post hoc basically means looking at your data after the fact and twisting your interpretation to perfectly fit your favorite theory.

It's like shooting an arrow into a blank wall and then walking up and painting the bull's eye right around it.

The author gives two highly specific damning examples of this in the research.

First, a study by Gruesler and Hammond.

Yes, they tested schizophrenic patients and found a left ear deficit in recalling digits.

Now logically, because the left ear feeds the right brain, you would think this points to a right hemisphere problem.

But instead, they argued that because verbal encoding is a left hemisphere activity,

a left ear deficit actually proved a left hemisphere impairment.

They completely painted the bull's eye.

The second example is from Gur.

Gur found that schizophrenics were faster at processing successive pictures.

And this specific pattern is normally seen in patients who have right brain damage.

So what did Gur conclude?

That this proved the left hemisphere was overactive.

They could have just as easily concluded the right hemisphere was defective, but they contorted the data to prop up the left hemisphere overactivation theory.

The overarching conclusion of the chapter is that neuropsychiatry is still an immature field.

You can use post hoc interpretations to make the messy data fit almost any of those four models.

We just don't have a perfectly unified theory yet.

However, the one undeniable conclusion, the entire point of the

neurology and psychiatry is that psychiatric disorders absolutely do have a neuropsychological dimension.

Even if the exact wiring faults are still a mystery, mental illness is fundamentally rooted in the physical tissue of the brain.

Absolutely.

As you close your textbook and get ready to walk into this exam, the author leaves us with a profound philosophical thought.

It's a heavy one.

If our highest levels of thinking, feeling and consciousness, the very things that you are governed by these physical systems, what does it mean when a simple misfiring wire, a tiny lesion or a disconnected lobe fundamentally changes who we are?

It completely reframes how we think about human identity and free will.

It forces us to realize that the mind is the brain and when the machinery breaks, the mind transforms with it.

You've got the anatomy, the mechanisms and the theories.

You are absolutely ready for this exam from the last minute lecture team.

Thank you so much for joining us on this deep dive and good luck.