Last LectureLast Lecture

Dichotic ListeningDichotic Listening The corpus callosum & The corpus callosum &

resource allocationresource allocation HandednessHandedness Broca’s Aphasia Broca’s Aphasia

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This LectureThis Lecture

Wernicke’s aphasiaWernicke’s aphasia The Wernicke-Geschwind ModelThe Wernicke-Geschwind Model Category-specific semantic deficits Category-specific semantic deficits

and the representation of meaningand the representation of meaning Introduction to the Frontal LobesIntroduction to the Frontal Lobes

Remember the Wernicke-Geschwind model?Remember the Wernicke-Geschwind model?

Broca’s area: forms detailed Broca’s area: forms detailed coordinated plans for language coordinated plans for language production (speech, writing, production (speech, writing, covert/rehearsal)covert/rehearsal)

Explains dysfluency and poor Explains dysfluency and poor articulation in Broca's aphasics.articulation in Broca's aphasics.

ButBut comprehension is not comprehension is not perfect...perfect... 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.

AgrammatismAgrammatism

Disproportional difficulty reading and producing Disproportional difficulty reading and producing function words.function words.

Difficulty using & understanding grammarDifficulty using & understanding grammar

Modification to Modification to Wernicke-Geschwind Wernicke-Geschwind modelmodel Broca's area:Broca's area: Plan for coordinating language production Plan for coordinating language production Understanding and using syntax.Understanding and using syntax.

Wernicke's aphasiaWernicke's aphasia

Examiner: Can you tell me a little bit about why Examiner: Can you tell me a little bit about why you’re here?you’re here?

Patient: Sine just don’t know why, what is really Patient: Sine just don’t know why, what is really wrong, I don’t know, cause I can eaten treffren wrong, I don’t know, cause I can eaten treffren eatly an everythin like that I’m all right at eatly an everythin like that I’m all right at home.home.

(Excerpt from Kertesz, 1980; quoted by Carlson, 1994)(Excerpt from Kertesz, 1980; quoted by Carlson, 1994)

Symptoms of Wernicke's aphasiaSymptoms of 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 inappropriatelywords used inappropriately nonsense words (neologisms) --> "word salad"nonsense words (neologisms) --> "word salad" meaning expressed in roundabout way meaning expressed in roundabout way

(circumlocution). (circumlocution). Comprehension: severely impaired.Comprehension: severely impaired.

According to Wernicke-Geschwind modelAccording to Wernicke-Geschwind model

Wernicke's AreaWernicke's Area ... ... DOES NOT STORE MEANING!DOES NOT STORE MEANING! stores memories of sound sequences that stores memories of sound sequences that

constitute words.constitute words. translates auditory input into phonological forms translates auditory input into phonological forms

that can then that can then accessaccess semantics. semantics.

Interpretation of Wernicke's area in actionInterpretation of Wernicke's area in action

Understanding spoken language:Understanding spoken language: Primary auditory cortex (41/42) -> Wernicke's A. (22) -> semantic Primary auditory cortex (41/42) -> Wernicke's A. (22) -> semantic

networks distributed throughout the brain.networks distributed throughout the brain.

Spontaneous speech: "cognitive" areas send input to Spontaneous speech: "cognitive" areas send input to Wernicke's area:Wernicke's area:

Cognition -> Wernicke's A. (22) -> arcuate fasciculus -> Broca's Cognition -> Wernicke's A. (22) -> arcuate fasciculus -> Broca's A. (44)-> Primary motor cortexA. (44)-> Primary motor cortex

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PET activation during listeningPET activation during listening

According to the Wernicke-Geschwind model...According to the Wernicke-Geschwind model...

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

SemanticsSemantics Angular gyrus (39) translates visual code to a form accessible by Angular gyrus (39) translates visual code to a form accessible by

Wernicke’s a. Wernicke’s a. grapheme --> phoneme translationgrapheme --> phoneme translation

Wernicke’s a. translates to a form that can access meaning.Wernicke’s a. translates to a form that can access meaning.

Implication: Reading requires phonological recoding via Implication: Reading requires phonological recoding via Wernicke’s A.Wernicke’s A.

Where is meaning stored?Where is meaning stored?

Wernicke’s area does Wernicke’s area does notnot store meaning, so store meaning, so where is it stored?where is it stored?

Meaning is represented across a network of Meaning is represented across a network of brain areasbrain areas Different brain areas contribute to different kinds of Different brain areas contribute to different kinds of

knowledgeknowledge

How do we know this?How do we know this?

Loss of SEMANTIC KNOWLEDGELoss of SEMANTIC KNOWLEDGE:: can’t recognize, describe from memory, or answer questions can’t recognize, describe from memory, or answer questions

about objects.about objects.

Category -specific deficits:Category -specific deficits: Some patients cannot recognize living things (plants/animals) Some patients cannot recognize living things (plants/animals)

but can recognize man-made things (tools/instruments)but can recognize man-made things (tools/instruments) Opposite pattern also reported (non-living things-impairment)Opposite pattern also reported (non-living things-impairment)

Double dissociation: separable representations for difference Double dissociation: separable representations for difference categories of knowledge.categories of knowledge.

PET evidence: Category-specific activations (Martin et al., 1996)PET evidence: Category-specific activations (Martin et al., 1996)

Subjects identified pictures of animals and toolsSubjects identified pictures of animals and tools Certain visual areas more active for animals Certain visual areas more active for animals Left premotor area more active for tools.Left premotor area more active for tools.

Semantic representation:Semantic representation:

- tools represented by function.- tools represented by function.

- living things represented by visual/sensory features.- living things represented by visual/sensory features.

The Role of LanguageThe Role of Language

Language ability sets us apart from other Language ability sets us apart from other animals.animals.

Is language what makes us uniquely human?Is language what makes us uniquely human?

Phineas GagePhineas Gage

Railroad worker who Railroad worker who experienced head trauma.experienced head trauma.

He survived.He survived. Drastically changed his Drastically changed his

personality.personality. ““Gage was no longer Gage,” Gage was no longer Gage,”

according to his friends.according to his friends.

The Frontal Lobes

Claim: The frontal lobes mediate those Claim: The frontal lobes mediate those abilities that make us uniquely human.abilities that make us uniquely human.

Herein lies the riddle... What makes us Herein lies the riddle... What makes us uniquely human?uniquely human?

The Frontal LobesThe Frontal Lobes

3 natural boundaries3 natural boundaries posterior: central sulcusposterior: central sulcus inferior: Sylvian fissure (lateral fissure)inferior: Sylvian fissure (lateral fissure) medial/inferior: corpus callosummedial/inferior: corpus callosum

Major SubdivisionsMajor Subdivisions

PrecentraPrecentral (motor cortex): Area 4l (motor cortex): Area 4

PremotorPremotor: : Areas 6 and 8 (including Areas 6 and 8 (including

supplementary motor) supplementary motor) 44 (Broca’s area)44 (Broca’s area)

Prefrontal:Prefrontal: dorsolateral: Areas 46, 45, 9, 10dorsolateral: Areas 46, 45, 9, 10 ventrolateral: Areas 11, 47ventrolateral: Areas 11, 47 orbital: 11orbital: 11

Anterior Cingulate:Anterior Cingulate: medial: Areas 24, 25, 32medial: Areas 24, 25, 32