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In previous module, we discussed some basic functions of the human brain

including motor control, sensation, vision, and fine motor movements.

In this module, we will be discussing some of the higher functions or

cognitive functions if you will and how those are represented in brain systems.

Cognition is the mental action or process of acquiring knowledge and

understanding through thought, experiences and the senses.

And it usually includes reasoning, memory, attention, and language.

So I'll now step through a couple of examples of brain systems

that support these types of cognitive function.

Obviously, there's a continued research going on trying to figure out

exactly how those systems give rise to cognition.

But there are number of aspects that we will know, how they work and

how they are supported in the brain.

For example, in language, Pierre Paul Broca was a French surgeon and

an anatomist who describes among several others, but two important patients.

Leborgne was unable to produce any words or phrases,

when he was evaluated back in 1861 by Broca.

And a second patient Lelong had severely reduced ability to produce speech.

Upon autopsy Broca as an anatomist and surgeon examined their brains and

noticed that in both patients there was a very specific area that was damaged,

as you can see in the bottom center image.

It was damaged to the posterior inferior frontal gyrus which has now

become known as the Broca's area.

Patients who have this difficulty with language due to damage to Broca's area,

are referred to as aphasia patients.

They can understand words and simple sentences,

they know what they want to say.

But they're absolutely unable to generate fluent speech.

They're unable to create the grammatical structure of a sentence and

express their thought.

In the example of patient Leborgne, in fact he was only able to express one word,

which was ten, which became his nickname.

Lelong was able to utter some very simple words, just a few of them and

some simple verbs, but could otherwise not produce significant or complicated speech.

Carl Wernicke was a German psychiatrist and neuropathologist and

he know that at certain patients had language problems and

had not had any damage to Broca's area.

Upon autopsy, he noticed a different area of the brain was affected,

as you can see again in the center bottom image.

It included damage to a posterior section of the superior temporal gyrus,

which became known as Wernicke's area.

Patients with Wernicke's aphasia, which is known as receptive aphasia,

have an impaired comprehension of spoken and written word.

So they're able to generate words, they're able to generate basic language, but they

have significant difficulty understanding either spoken or written language.

Again, they're unable to departs the sentence structure that we

are normally able to decipher and understand the meaning of.

So when we combine these findings from these two scientists,

we note that receptive language, what was said or read,

depends on an area defined by Wernicke.

In the posterior aspect of the brain, there is what to say, which is usually

processed by the frontal areas of the brain in response to what we heard.

Then there's a determination of expressive language which is how do we

explain ourselves, how do we prepare our response which depends on Broca’s area.

This can be either in silent, or in writing, or speaking.

Depending on the Wernicke or the motor cortex such that expressive language gets

sent to the motor cortex if we want to employ our vocal chords or

use handwriting to express ourselves.

Or when it concerns silent thought, which still contains language,

that information is sent back to one of these area, so here we see a network of

brain areas that is responsible for both receptive and expressive language.

Another example was the famous case of Phineas Gage.

He was a railroad worker who back in 1848 was involved in a horrible accident.

He was responsible for blowing up rocks using explosives and

he was using an iron rod to temp down an explosive compound in a hole.

He stopped paying attention for a just a minute and unfortunately,

with the metal rod caused a spark on the rock which ignited the gun powder that he

was using, and set the rod through his skull.

It entered on the left side of his face as you can see on the right hand side image

and exited the top of his head, causing extensive damage to the frontal lobes.

Now this explosion was massive, ultimately they found the metal

rod some 80 feet from where Phineas Gage was working.

So it caused a tremendous amount of damage and the recovery was fairly extensive, but

he does survive the accident.

On the very right hand side, again you can see the trajectory of the metal rod and

the type of damage that it caused to the brain.

Again, as I said he survived the accident and

he was able to function in many different ways.

His speech and motor control were largely preserved,

he was able to understand other people and express himself,

or be it rudimentary, but he had a severe personality change.

He became very irritable and aggressive and

in the expression of his peers he was very hard to along with.

So he displayed very significant portionality changes as a result

of this accent, as a result of the damage to his frontal lobes.

In the memory domain, we've learned a lot from patient, H.M.,

who was arguably one of the most famous neuroscience patients ever described.

H.M., depicted here on the far left suffer from severe epileptic seizures.

He saw a neurosurgeon, Dr. Scoville, who in 1953 performed a brain surgery

to remove bilaterally the hippocampus, amygdala, and the surrounding cortex.

As you can see in the schematic on the right hand side.

These are important structures in the medial temporal lobes of the brain.

On the MRI images on the bottom,

you can see the amount of tissue that was excised by the surgeon bilaterally.

The green demarcation shows the medial temporal lobes, both on the left and

the right.

And what is outlined in pink or reddish color is the extent

of the resection that was performed on this patient.

The surgery that was done before by the surgeon but

never on both sides of the brain simultaneously.

After recovery, the surgeon and

neuropsychologists noted that H.M., had intact language.

He had a normal IQ and working memory, had no trouble with motor control.

But he had a very significant inability to learn new information.

He was unable to learn or form new memories.

He was also unable to remember anything from after the surgery and for

a distinct period of time prior to the surgery.

The only things that he could remember were essentially memories from his

childhood.

So from these studies, it was concluded that the structures of the medial temporal

lobe are critically important for memory.

Here's a quote from patient H.M.,

which gives a very nice example of what that's like.

He says, right now I'm wondering have I done or said anything amiss?

You see at this very moment everything looks clear to me, but

what happened just before?

That's what worries me.

It's like awakening from a dream, I just don't remember.

So he lived very moment to moment in the sense that he was unable to retain what

was going on or what his history was for more than just a few minutes at a time.

Similarly patient E.P., suffered from a herpes simplex virus

which also affected the hippocampus in the medial temporal lobe.

Causes severe damage, as you can see in the MRI image at the bottom.

On the left hand side is patient H.M.

with the surgical resection that we just discussed.

On the right-hand side, you can see patient E.P., who has less extensive but

similar damage on both sides of the brain to the medial temporal lobe as shown here.

He also experienced an intact language ability, intact IQ, working memory,

as well as motor control.

But again, had a very significant impairment in retaining new

information and creating new memories.

From this research and a lot of research since then we have learned that

the structures of the middle temple of as indicated in the top

left are critically important for forming and creating new memories.

Particularly memories for facts and events or episodes from our personal lives.

In the bottom, you can see a cross section of the brain and

as well as the hippocampus, the structure that is thought to

be very critically important for this type of memory.

Refer to as the hippocampus which is Latin for

sea-horse to which is perceived it's name as you can see in the bottom image.

On the right side, we see the hierarchy of the structures of the medial temporal

lobe, that have since been studied extensively, to determine and to conclude

that this area of the brain is critically important again for that type of memory.

But patient H.M., was tested with a number of different tasks.

In one task, he was asked to draw a star,

you see the star on the bottom of the screen, with two double lines.

He was asked to use a pencil and draw between those two lines,

draw the star without touching the lines.

So this is obviously a somewhat tricky task.

It was made even more difficult by asking him to do it while looking in a mirror.

So he wasn't able to directly observe his hand in his work.

He had to do it in a mirror image.

Now what you see on the right hand side in the diagram,

is that over the course of several days he did improve by making fewer and

fewer errors completing this task.

That is, he was learning how to do this task.

He was making improvements in his performance on the task.

Yet when you asked him if he had completed this task before,

he would say that he had no memory of ever doing this task before.

This led Brenda Milner a famous neuropsychologist who studied H.M.,

extensively to conclude that there must be multiple memory systems in the brain.

The medial temporal system which I just talked about, responsible for

memory for facts and events as well as a different memory system which

may be important for motor learning.

And in fact from much subsequent research we have learned that there are multiple

systems in the brain in fact that support memory functions.

The medial temporal lobe being the most prominent one but

also the basal ganglia which consists of a number of brain structures as

shown in the bottom right hand image.

Including the caudate nucleus and the thalamus as well as the putamen.

The basal ganglia are critically important for fine motor planning and movements.

And the striatum which is predominantly the caudate and putamen are involve in

the reward learning, reward reinforcement as well as some forms of learning,

particularly motor learning and stimulus response types of learning.

So here we see examples of different systems in the brain

that support our different types of memory functions.

There are other areas of the brain that have very,

very specific cognitive functions.

Highly specialized areas.

For example, the fusiform face area, as shown here on the top

right is critically important for recognizing faces.

The extrastriate body area, shown in the red circle on the bottom image,

is critically important for recognizing body parts or

parts of the body as whole or individual parts of the body.

So highly specialized areas in the brain that form a very specific function.

People with damage to the fusiform face area are called prosopagnosia patients.

Even though they're able to recognize the individual pieces of a face they're unable

to recognize the person and name the person.

They often have to identify a person by listening to them talk, or

some other means.

They're not able to recognize the face as a person they know.

So they have an inability to recognize familiar faces.

So, in this module, we've discussed a number of cognitive functions that

have known structures in the brain that support them.

In the previous module, we discussed the primary motor cortex and

the somatosensory cortex.

We've talked about visual processing and motor planning.

We've also talked about the basal ganglia in this particular module, supporting

memory function, language functions in the Broca and Wernicke's areas, and

several other areas that we have well established the known functions of.

But as you can see from this module, a lot of this information was

learned from studying patients who have extensive damage to the brain.

Patients who were involved in accidents or

patients that experienced viruses that caused damage to the brain.

Really significant trauma that allowed us to draw these types of conclusions.

In the next module, we're going to talk about neuropsychological assessment.

Which is a fine tuned assessment method for

trying to figure out what areas of the brain are responsible for

very specific functions that are important for cognition.

Organization of Cognitive Domains

Fundamental Neuroscience for Neuroimaging

Meet the Instructors