Website: Mary Louise Kean, UC Irvine

The brain

Modularity

Different areas of the brain are specialized for different functions. It is possible to divide the brain up into different modules which can cooperate in performing the functions of pereception, movement, thought, and speech.

One important brain module is the language module.

We shall see that there our linguistic abilities really require several modules that cooperate.


Split brain

In the human brain, the two hemispheres are joined together by fiber pathways. The major connective structure is the corpus callosum.

In split brain patients (severe epileptics) this is cut.  

 




In the brain, the right side of the brain controls and processes information from the left side of the body and the left side of the brain controls and processes information from the right side of the body.



 





 



For example, the right visual field is projected back to the left visual cortex. The left visual field projects to the right visual cortex. Thus in right handers body control on the left side of the brain seems to be dominant and in left handers it's the right side.  



     
     
     
     
     

Differences between the two hemispheres of the brain

Body control and vision processing are two of many functions which are shared by both sides of the brain.

But many functions are specialized for one side of the brain or the other. We say they are lateralized.

Some function differences in the two hemispheres:

    Left Right
    Emotion Emotion
    Language Melody
    Rhythmn Face Recognition
    Temporal Order Pattern Recognition
      Spatial Orientation

Consequences for Split-Brain Patients

Studies on split brain patients (California Institute of Technology and the UC-Los Angeles).

Chief result: The two hemispheres function largely independently, dealing with separate streams of information. Some tasks require communication between the two hemispheres. These tasks cannot be performed by split-brain patients.


Experiments

Setup I:

Setup II: Composite Pictures. Eyes and bees.

Split-brain patients invariably identify the third picture as an eye. Why?


 

Because there is no way to communicate between the right and the left hemispheres, the split-brain operations provide scientists with valuable information about the lateralizations of the human brain. Especially the language function.



 
 
 
 
 


Brain injuries

Scenario I  

Mr. Smith is in the hospital. A doctor comes to examine Mr. Smith, who is, at the time, sitting on the edge of his bed. The doctor taps him on the knee resulting in a reflex.

    Doctor Mister Smith, salute!
    Patient [unable to salute]
    Doctor Make a fist with your right hand!
    Patient [unable to respond appropriately]
    Doctor Mister Smith, stand like a boxer.
    Patient [immediately strikes a boxer's stance, making fists with his right and left hands.]
    Doctor Mister Smith, stand at attention.
    Patient [immediately stands at attention.]
Question  

What's going on?

Preliminary
Observation
 

Mr. Smith's reaction demonstrates that he has motor control, he can make a fist, and he can comprehend language. Thus Mr. Smith is suffering from neither a "motor" (body movement) dysfunction nor from an inability to comprehend spoken language.

What this
example shows
 

This example demonstrates how certain brain injuries affect the interaction between two skills.

There is an area of the brain concerned with motor skills, movement of part of of the body.

There is an area of the brain connected with language.

Smith has both movement skills and language skills, as demonstrated by the fact that he could make the boxer's pose when asked to, which involved both understanding a command and making a fist.

It's in talking about making movements that a problem arises.

Diagnosis   This condition is called apraxia. Apraxia is a limitation or the inability to carry out certain kinds of voluntary movements upon verbal command.
Source of
Problem
 

We hypothesize that's what going on in the brain is a disconnection of the language system from the motor system. So this is strongstrongly evidence that there are two distinct areas of the brain responsible for language and certain kinds of movements.

Moral  

It's easy to get confused.

If all we had observed was that Mr. Smith could not perform certain kinds of motion commands we might have concluded he had damage to either the motor areas or the language areas.

In fact, neither would have been right.

Study of
Brain Disorders
 

It is by studying such disorders and various other disorders which arise as a result of brain damage, e.g., stroke or head trauma or penetrating head wounds, that scientists have learned most of what is known about the functions of the various areas of the human brain. In fact, considerable research on human brain and behavior is done with stroke patients. This is because strokes can cause small localized lesions which disrupt behavior. When a small area of the brain is damaged, the effect of it on behavior can yield information about the function of the damaged structure. There are also situations where the consequence of a stroke is a massive damage to the brain. These are also studied.

The best kinds
of brain injuries
 

For research purposes, people who have had closed head injuries are not of great interest because their brain injuries are diffuse. The reason is that closed head injuries typically arise when a person's head bashes against a fixed object, such as the steering wheel or dashboard in a car during an accident. The brain begins to move in response to the impact. If the impact is hard on one side, the brain will bounce back against the other side of the skull and then back again. The consequence is that both sides of the brain get damaged. Thus, closed head injuries often cause diffuse brain damage. In an effort to understand how the brain functions, these type of injuries are not very useful because they do not provide precise enough information.

WWI really
helps!
 

Wars are really great for the study of brain functions, but only up through World War One. This is because of the bullets used at the time. These bullets often penetrated the skull and then stopped inside of the brain. Today's bullet tend to explode and damage the brain, and war casualties who have been shot in the head frequently die or suffer very serious and far reaching head injuries, i.e. brain damage, excluding the opportunity for precise information.

Nowadays  

Nowadays, brain research scientists tend to focus on stroke patients because of their often very discrete injuries.

Scanning/Visualization technology: Magnetic Resonance Imaging (MRI), Positron emission tomography(PET) provide information previously unavailable or available only t hrough autopsies and/or surgery. (Fig. 2.4,2.5 text, pp. 38, 39)



Non-linguistic impairments

Agnosia (Typical Brain Area: superior right parietal lobe)

The word agnosia (from the Greek) basically means not knowing.
    a- gnosia
    not/without knowing
Scenario II  

Mr. Jones is in the hospital. Doctor enters the room and pours out a collection of common objects on the table, including a set of keys, a comb, a quarter, a wallet, and a paper clip.

    Doctor Mister Jones, please find the keys.
    Patient [picks out comb]
    Doctor [Puts comb back]. Please find a quarter.
    Patient [selects paper clip]
    Doctor Please pick out the wallet.
    Patient [immediately picks out the wallet.]
    Doctor [Clears off table except for keys.] Mister Jones, I'm going to read out a list of words. Let me know when I get to a word that matches what's on the table. Book. Glasses. Buckle. Keys ---
    Patient [immediately makes a gesture.]
Diagnosis  

This behavior is characteristic of a person with visual agnosia.

Visual agnosia is characterized by:

  1. Inability to identify names or describe visually projected objects.
  2. Inabilty to select an object from an array.
  3. At best, can draw or copy major features of an object.

The main features of the pictures drawn by agnosics are not coordinated.

Action vs.
talking about
actions
 

Agnosia patients can drive their cars home.

A dissociation between sensory knowledge for action and knowledge of how to talk about objects. Other dissociatons as well (picture-drawing).

Other types of agnosia


Sylvian Fissure separates temporal lobe from parietal and frontal lobes

Sensory
Neglect
 

Sensory Neglect (Typical Brain Area: Parietal lobes). A patient with a right parietal lesion ignores, in large part, the left side of the world.

Scenario II (Sensory Neglect)

 

Doctor [hands the patient a page with evenly distributed alphabetic letters on it] Can you please circle all the A's?
Patient {Works for a while, then hands back the page. All the A's on the right side of the page are cirecle. All those on the left side have been ignored.]
Doctor [Hands the patient a blank sheet of paper.] Can you please draw a clock for me?
Patient [Patient works for a while, then returns the sheet of paper. The clock looks like this:]


The clock is all on the right side.
The left side is completely neglected.


Doctor Can you show me your right hand?
Patient [Shows right hand.]
Doctor Can you show me your left hand?
Patient I can't.
Doctor Why not?
Patient The other doctor sent it away on vacation. [Pretty weird!]
Doctor Okay, then, can you show me your eye?
Patient [Points to right eye.]
Doctor [Calls a large group of teaching assistants into the room. They arrange themselves on both sides of the bed, four on the right, six on the left.] Can you count the teaching assistants for me?
Patient Four.
Doctor Okay I see four over on this side of the bed, but what about these people?[indicates the teaching assistants on the left side of the bed.]
Patient They don't count. [Pretty weird!]
Doctor [Gives a prearranged signal and one of the teaching assitants who "don't count" suddenly throws a ball at the patient.]
Patient [Ducks and the ball sails harmlessly over her head.]

Sensory
Neglect
Summary
 

People suffering from sensory neglect do have some awareness of the neglected side of the world. The experiment with the ball shows that the patient does process sensory input from the neglected side. Nor do these patients walk into doors and corners on the neglected side. Yet, their ability to consciously report and deal with that part of the world is severely compromised.

Other
Agnosias
 

  1. Prosopagnosia [Face Recognition]: (Typical Brain Area: superior right parietal lobe near visual cortex): Inability to distinguish between human faces, even among family members.
  2. Recognizing a Face as Face (Typical Brain Area: inferior temporal lobes, both sides) Inability to recognize that a face is a face.
     

    Illustration of faces



    For people without brain lesions, a face is recognized as a face even when upside down, but not when the components of the face are not in proper places. For people with the brain lesion recognition of all three pictures may be affected.

  3. Autotopagnosia (Talking about your body) The word "auto" means self, and "topos" means place, referring to the place of the one's own body.
    Doctor: Can you show me your right hand?
    Patient: Well, I did see it, it was around here somewhere.
    I guess I left it down in the cafeteria when I had lunch.
    Doctor: All right, could you please point to my right hand?
    Patient: [Points to doctor's right hand.]
    Doctor: All right, could you please point to your eyes?
    Patient: Oh, um, geez, oh yeea, they're over there.
    [points to a wall of the room.]
    Doctor: All right, could you please point to my eyes?
    Patient: [points to the doctor's eye.]
    Doctor: Now, would you point to your nose?
    Patient: Oh, yeah, it's over there too.[indicates wall.]
    
    Such patients are normally better at identifying body parts belonging to other people; their most extreme deficit is in relating to their own body parts.

  4. Finger agnosia One form of agnosia which is associated with the left parietal, temporal lesion. Finger agnosia is characterized by the lack of knowledge about one's hand. If a person suffering from finger agnosia is asked to draw a hand, the patient will draw a picture somewhat like this:



Aphasia: Language Impairments

Language is probably the most remarkable and unique capacity humans have. In this capacity, humans differ from all other animals. Human linguistic capacity is represented in the left hemisphere of the human brain in both right-- and left--handers, except in extremely rare cases.

This triangular area (area located around Sylvian fissure) is where language is located in the brain.

A stroke causing damage in this area will cause a language deficit. The deficit will be restricted to the ability to use language. There fluent and disfluent aphasiacs. Of the disfluent aphasiacs, an important special case is Broca's aphasia. Of the fluent aphasiacs, an important special cxase is Wernicke's aphasia

The two main language areas are Broca's area, which is located in the frontal lobe, and Wernicke's area, which is located in the temporal lobe.

Broca's Aphasia

Damage to Broca's area results in Broca's aphasia. Produces both comprehension and production deficits.

1. Long pauses between words. [This is called dysprosody.]

2. Agrammatism. Agrammatism is the tendency to omit function words as well as endings such as -ed in indicating past tense. Function words are words which tie sentences together: the, of, is, by, a, etc.

3. Some sound changes, simplification of consonant clusters:

    It's hard to eat with a speoon
    har eat wit poon
This often leads to accompanying dyslexia (reading deficits) and dysgraphia (writing deficits), for example, writing spoon as poon.

4. Frustration. They know there's something wrong.

In sum, there is a lot of evidence that Broca's is simply a production deficit (the once prevailing view). But there is also evidence that it is something more.

Tests demonstrating comprehension deficits


Sentence given:     Bill chased Mary

Patient response: Bill is the chaser and Mary is the chasee (or the one who is being chased). [Correct]

Sentence given:     Bill was chased by Mary

Patient response: Random.

Picture task: Candidate pictures for the sentence "The dog bit the postman" :
 


Sentence given     "The dog bit the postman."

Patient response: Invariably correct.

Sentence given     "The dog was bitten by the postman."

Patient response: Patient points to picture representing the postman being bitten by the dog.

In order to understand the difference between actives and passives, patients must pay attention to function words and grammatical endings:

    bit
    be bitten by
So passive sentences are hard for Broca's patients to understand.

Use of real world knowledge informs guesses, not use of grammar.

Question: What would happen if we give the sentence: "The postman bit the dog". Which picture would the Broca's patient point to?

Answer: I don't know. My guess: They point to the right picture.

Another example to support this: Japanese. A "case" language. Two ways of saying "Taro hit Hanako".

    (1) Taro- ga Hanako- ni nagutta
      Taro- SUBJECT Hanako- OBJECT hit
    (2) Hanako- ni Taro- ga nagutta
      Hanako- OBJECT Taro- SUBJECT hit

    Taro hit Hanako.
Broca's patients point to the right picture when given sentence (1) and do no better than chance when given sentence (2). The reason: in order to understand sentence (2) "normal" speakers have to pay attention to the little function words "-ga" and "-ni". And this is precisely what Broca's patients seem to be unable to do. [Hagiwara and Caplan (1990), Hagiwara (1993).]

Examples with complex syntax

  1. The apple that the boy is eating is red.
  2. The cow that the monkey is scaring is yellow.
Broca's patients: Do well at the picture matching task for sentence (1), but no better than chance at the picture-matching task for sentence (2).

  1. The cow that the monkey is scaring is yellow.
  2. The monkey that the cow is scaring is yellow.
These two sentences differ only in the arrangement of words, the syntax.

  1. The apple that the boy is eating is red.
  2. The boy that the apple is eating is red.

Note: In the sentence "The apple the boy ate was red" the italicized part is called a relative clause. It helps describe or pick out the particular boy we're talking about.

This shows Broca's patients have trouble with complex syntactic constructions when there's no extra information to help. [Caramazza and Zurif (1976)]

Word List Reading:

                    ant
                    tree
                    of
                    dog
                    be
                    house
                    bee
What Broca's patient reads: ant, tree, damn little word, dog, curses . . . damn little word, house, bee. Note the patient cannot read the word be, the function word, yet can read the word bee .

Summary of Problems for Broca's Patients

These patients and the lesions they have suffered clearly demonstrate that in human mental representation there is a systematic distinction between word groups such as nouns, verbs, and adjectives and functional elements such as of, and is and the etc. There is also a systematic difference between knowledge of word meanings and knowledge of syntax, knowledge of how the arrangements of words affect meaning.

There is also a second important point. In Broca's aphasia, there are parallel deficits in all domains of language use: speaking, comprehension, reading, and writing. Broca's aphasics have their cognitive and mental functions intact. Thus, under normal circumstances (i.e. when nasty scientists are not trying to trick them) these people show, for all intents and purposes, quite good comprehension in a practical sense. In functional sense, i.e. in terms of brain architecture, the inference from these results is that Broca's area plays a primary role in all modalities of language use.


Wernicke's Aphasia

Lesions in Wernicke's area lead to what is called Wernicke's aphasia.

Semantic paraphasias: For instance, they may say arm when they mean leg.

novel word structures.

    sickser means "doctor"
Cpombines:
    the word sick with the ending -er
This word, if it existed, might mean something like one who engages in some activity related to sickness.

Also use complete nonsense words:

    bangahanga bangahanga bangahanchepie

Anomia ("no names"): cannot reliably find and use nouns (although often they substitute a semantically related word for the appropriate word).

Doctor [Showing, a pen] Can you tell me what this is?
Patient Geez, you know . . . isn't that funny, oh I know, it's one of those things, . . .it's. . . it's funny, you know . . . I know that it is . . . you know . . .it's hummmm . . . it's one of those things.
Doctor [Produces a comb] How about this?
Patient Ooohhh. . . . isn't that funny . . . I'm getting old . . . it's so terrible, ohhh . . . you know . . . I just . . it's that funny, oh geez . . you know . . . I know, it's that thing you use to comb your hair with.

Note that the patient uses the word comb as a verb: ". . . the thing you use to comb your hair with." Yet she could not associate the noun "comb" with the object. The deficit appears to be related to naming, specifically to the use of nouns rather than verbs.

Patients with Wernicke's aphasia also suffer from comprehension problems, i.e. they have trouble understanding what is being said to them.

In summary, the problems associated with Wernicke's aphasia are:


Summary and Diagnosis of disorders

Three tests involved with naming:

  1. Naming: The patient is presented with, say, a set of keys and the patient is asked to name the object.
  2. Name selection: The patient is shown an object, say a set of keys. The person conducting the test will recite a list of names of objects. The task is to indicate when the correct name is said.
  3. Object selection: In the third test objects are arranged in front of the patient. The patient is then asked to select the object the tester asks for, e.g. "Point to the keys" or "Point to the toothbrush."

In sum: 

                   Visual Agnosic            Aphasic

1. Naming         No name or                Correct name 
                                            (Broca's aphasia)

                  inappropriate name        Semantically related word 
                                            or neologism
                                            (Wernicke's aphasia)

2. Name 
   Selection      Random                    Good (Broca's aphasia)
                                            Good (Wernicke's aphasia)

3. Object         Random                    Very good (Broca's aphasia)
   selection                                Good (Wernicke's aphasia)

Summary of differences between Wernicke's and Broca's patients.

  1. Picture test
  2. Word list reading Wernicke's patients will do equally well at reading all words; Broca's patients will have special trouble with function words (prepositions, conjunctions, articles) but may have troubles with other words as well, sometimes producing semantically related words.
  3. Production differences: Broca's patients show agrammatism, long pauses, are aware of their difficulties. Wernicke's use grammar and function words well, produce semantically related words or nonsense words without realizing it, may confabulate to explain their difficulties finding words.

Patient Scenarios

To be done in class:

  1. Patient Scenario 1
  2. Patient Scenario 2
  3. Patient Scenario 3
  4. Patient Scenario 4

Websites: Aphasia


http://www.stroke.cwc.net/niweb/faq.htm#14 different parts of the brain do

http://www.asha.org/speech/disabilities/Aphasia_info.cfm

http://fuzzy.iau.dtu.dk/aphasia.nsf

http://www.asha.org/speech/disabilities/index.cfm

http://www.med.harvard.edu/AANLIB/home.html


http://www.lsadc.org/faq/index.php?aaa=faqstrok.htm
 

What's where?

  1. Nouns vs Verbs:

      Some evidence of different lesion locations affecting nouns and verbs differently in production.

      Lesion closer to motor area affected verbs more.

  2. Broca'a area: Syntax? Or is it something more general and NOT language specific (Sequencing: The planning of complex motor sequences: explains agrammatism, dysprosody.)
  3. Wernicke's area: Semantics?