Last Lecture

Hemispheric differences in Hemispheric differences in the Bisected Brainthe Bisected Brain

Functions of the corpus Functions of the corpus callosumcallosum

Hemispheric Asymmetries in Hemispheric Asymmetries in the Normal Brainthe Normal Brain Methods and theoriesMethods and theories

This Lecture

Dichotic ListeningDichotic Listening The corpus callosum & The corpus callosum &

resource allocationresource allocation HandednessHandedness Functions of the corpus Functions of the corpus

callosumcallosum The aphasias The aphasias

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Announcements

Quiz next weekQuiz next week Study guide on the web after class todayStudy guide on the web after class today Cognitive Neuroscience chapter 8 only Cognitive Neuroscience chapter 8 only

sections on Language and the Brain (303-312)sections on Language and the Brain (303-312)

ba ga

ba ba ba

ba

ga

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left left leftright right right

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Both ears project Both ears project bilaterallybilaterally

Contralateral projection is Contralateral projection is strongerstronger

With dichotic input With dichotic input the ipsilateral ear’s the ipsilateral ear’s input is supressed.input is supressed.

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The Corpus Callosum and Processing Resources

Resource: basic raw materials needed to get a Resource: basic raw materials needed to get a task done.task done.

Each hemisphere has some competancy with Each hemisphere has some competancy with most tasks.most tasks.

As task difficulty increases, both hemispheres As task difficulty increases, both hemispheres are recruited to meet task demands.are recruited to meet task demands.

Two Comparison ConditionsAcross Field ComparisonAcross Field Comparison

(from(from Banich & Belger, 1989Banich & Belger, 1989))Unilateral Processing Bihemispheric ProcessingUnilateral Processing Bihemispheric Processing

+A B

A

Within Field ComparisonWithin Field Comparison

A

A

B

+A B

A

A

A

B

Three Levels of Task Difficulty

+

A B

A

Physical Identity Match: A-APhysical Identity Match: A-AName Identity Match: A-aName Identity Match: A-a

+

A B

A

C D+

A B

a

C D

3-Item Physical 5-Item Physical 5-Item Name3-Item Physical 5-Item Physical 5-Item Name

Sometimes, Two Hemispheres are Better than One...

For easier tasks For easier tasks within field within field matches are matches are faster.faster.

For harder For harder tasks across tasks across field matches field matches are faster.are faster.

3-PI 5-PI 5-NI250

350

450

550

650

750WITHINACROSS

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Functions of the Corpus Callosum

Unify the sensory world Unify the sensory world e.g. copies of inpute.g. copies of input

Information transmission Information transmission to access specialized processors to access specialized processors (more on this with (more on this with

case V.J)case V.J) to share products of cognitive processesto share products of cognitive processes

Allocation of resources (Banich task)Allocation of resources (Banich task)

Handedness

10% of the population is Left Handed10% of the population is Left Handed Left handers have different brain organizationLeft handers have different brain organization

70%LH

15%RH

15%both

Speech ControlLeft handers

95%LH

5%RH

Speech Control Right handers

What is left-handedness?What is left-handedness?

Case V.J.- Clues to handedness(Baynes et al)

a left hander w/ a left hander w/ normal speech & normal speech & language who language who underwent underwent callosotomy.callosotomy.

After surgery:After surgery: left hand single-left hand single-

letter writing - letter writing - perfectperfect

right hand entirely right hand entirely agraphicagraphic

Isolation of grapho-motor module

In VJ, writing In VJ, writing dissociates from dissociates from other language other language abilities.abilities. Writing in RHWriting in RH All others LHAll others LH

In JW & VP all In JW & VP all language language abilities are co-abilities are co-localized in LH.localized in LH.

70%LH

15%RH

15%both

Speech ControlLeft handers

Implications of V.J.

Writing module can be dissociated Writing module can be dissociated from other language modules.from other language modules.

Handedness may depend on Handedness may depend on laterality of writing module.laterality of writing module.

In all Left handers access to this In all Left handers access to this RH module may require the c. RH module may require the c. callosum.callosum.

Laterality of other language Laterality of other language modules may also vary in Left modules may also vary in Left handers. handers.

What are the other components of

language?

Components of Sound-based Language

PhonemesPhonemes- units of sounds that make up words- units of sounds that make up words MorphemesMorphemes- smallest unit of meaning- smallest unit of meaning SyntaxSyntax - grammar-- rules for combining words - grammar-- rules for combining words LexiconLexicon - stored representations of words (auditory/visual) - stored representations of words (auditory/visual) Semantics Semantics - meanings that correspond to lexical items- meanings that correspond to lexical items ProsodyProsody- intonation of speech (Right Hemisphere province)- intonation of speech (Right Hemisphere province) ArticulationArticulation- movements of the mouth and vocal tract for - movements of the mouth and vocal tract for

producing speechproducing speech DiscourseDiscourse - Linking of sentences into coherent narrative. - Linking of sentences into coherent narrative.

Production and comprehension of these Production and comprehension of these components are required for language.components are required for language.

Broca's aphasia

speech: labored, slow & nonfluent speech: labored, slow & nonfluent (awkward (awkward articulation, search for phonemes).articulation, search for phonemes).

paraphasic errors paraphasic errors (phonemic: pelsil for pencil)(phonemic: pelsil for pencil) responses make sense but are ungrammatical.responses make sense but are ungrammatical. greatest difficulty: verbs, articles, pronouns greatest difficulty: verbs, articles, pronouns

(generating & repeating)(generating & repeating) --> telegraphic speech --> telegraphic speech Comprehension is relatively sparedComprehension is relatively spared

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Cookie Theft Picture (BDAE)

Lesion locus of Broca’s aphasia

Is Broca’s aphasia simply a problem with vocal-motor coordination?

After all...Broca’s area After all...Broca’s area is near motor face is near motor face area...area...NO!!NO!!

No dysfluency after No dysfluency after hemifacial paralysis hemifacial paralysis from RH damage from RH damage

Dysarthria - a separate Dysarthria - a separate disturbance- lack of disturbance- lack of coordination of vocal coordination of vocal track.track.

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Broca’s aphasia has cognitive/linguistic properties

Better fluency for memorized phrases.Better fluency for memorized phrases. Singing may be more fluent than speech Singing may be more fluent than speech

--> Melodic intonation therapy--> Melodic intonation therapy Why should coordination problems affect Why should coordination problems affect

verbs/function words more than nouns???verbs/function words more than nouns??? Written output shows same errors as speech! Written output shows same errors as speech!

These features suggest more than a problem with These features suggest more than a problem with vocal coordination.vocal coordination.

Wernicke-Geschwind model

Broca's a.: forms detailed Broca's a.: forms detailed coordinated plans for coordinated plans for languagelanguage production (spoken, written, production (spoken, written, covert/rehearsal)covert/rehearsal)

Explains dysfluency and poor Explains dysfluency and poor articulationarticulation

ButBut comprehension is not perfect...comprehension is not perfect... Schwartz, Saffran and Marin, 1980Schwartz, Saffran and Marin, 1980

Poor syntax comprehensionPoor syntax comprehension Broca's aphasics poor at judging Broca's aphasics poor at judging

grammaticalitygrammaticality

Active: The horse kicked the cow.Passive: The cow was kicked by the horse.

Agrammatism...

difficulty using & difficulty using & understanding grammarunderstanding grammar

Modification of the W-G Modification of the W-G modelmodel

Broca's area:Broca's area: Plan for coordinating Plan for coordinating

language production language production understanding and using understanding and using

syntax.syntax.

Active: The horse kicked the cow.Passive: The cow was kicked by the horse.

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Wernicke's aphasia

Speech: phonetically & grammatically normal but Speech: phonetically & grammatically normal but meaningless.meaningless.

generally fluent, unlabored, well articulated. generally fluent, unlabored, well articulated. normal intonation (prosody).normal intonation (prosody). words used inappropriately, nonsense words words used inappropriately, nonsense words

(neologisms) --> "word salad"(neologisms) --> "word salad" meaning expressed in roundabout way meaning expressed in roundabout way

(circumlocution). (circumlocution). Cookie Theft description...Cookie Theft description...

"Mother is away here working her work to get better, but when she's looking "Mother is away here working her work to get better, but when she's looking into the two boys looking in the other part. She's working another time..."into the two boys looking in the other part. She's working another time..."

Comprehension: severely impaired.Comprehension: severely impaired.

Interpretation of Wernicke's aphasia

According to Wernicke-Geschwind modelAccording to Wernicke-Geschwind modelWernicke's AreaWernicke's Area

stores memories of sound sequences that constitute stores memories of sound sequences that constitute words.words.

translates auditory input into phonological forms that can translates auditory input into phonological forms that can then then accessaccess semantics. semantics.

meaning is stored in other cortical areasmeaning is stored in other cortical areas During spontaneous speech, "cognitive" areas During spontaneous speech, "cognitive" areas

send input to Wernicke's area:send input to Wernicke's area: Cognition -> Wernicke's A. (22) -> arcuate fasciculus -> Cognition -> Wernicke's A. (22) -> arcuate fasciculus ->

Broca's A. (44)-> Face areaBroca's A. (44)-> Face area

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READING

Reading According to theWernicke-Geschwind model...

Wernicke’s A. essential for reading...Wernicke’s A. essential for reading... Visual processing --> Angular gyrus --> Wernicke's A.--Visual processing --> Angular gyrus --> Wernicke's A.--

> Semantics> Semantics Angular G. (39) translates visual code to a form that can access auditory word Angular G. (39) translates visual code to a form that can access auditory word

code in Wernicke’s.A.code in Wernicke’s.A. Semantics must be accessed via the auditory (phonological) form of the word.Semantics must be accessed via the auditory (phonological) form of the word.

Implication: Reading requires phonological recoding via Implication: Reading requires phonological recoding via Wernicke’s area… or does it??Wernicke’s area… or does it??

PET evidence challenges this account Posner, Peterson, Raichle and colleagues (1988)Posner, Peterson, Raichle and colleagues (1988)

If auditory recoding is necessary for reading thenIf auditory recoding is necessary for reading thenreading and listening should activate the same brain areasreading and listening should activate the same brain areas

They do not...They do not... Implication- visual representation can access meaning directly Implication- visual representation can access meaning directly

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READING LISTENING