Language OrganizationClassic model

Sensory perception--comprehension (WA)--Broca’s (formulation, motor plan)--motor cortex (final common pathway)

Language OrganizationClassic model

Sensory perception--comprehension (WA)--Broca’s (formulation, motor plan)--motor cortex (final common pathway)

Classical conception of aphasia.

Paul Broca (1824-1880). Communication a la Societe d’Anthropologie (1865)” Je vous ai communique…….dix observations d’aphemie dans lesquelles on a trouve a l’autopsie des lesions diverses de la 3me circonvolution frontale…..Je persiste a penser que l’aphemie verbale, c’est a dire la perte de la parole sans paralysie des organes de l’articulation et sans destruction de l’intelligence est liee aux lesions de la 3me circonvolution frontale. Ma communication est relative a la singuliere predilection de l’aphemie pour l’hemisphere gauche du cerveau”Mr.Leborgne =Tan-

Tan died 4/17/1861

Mr. Leborgne died 4-17-1861 11am

at the age of 51.

MRI of Leborgne 4-15-1994

Voxel-based Lesion-Symptom Mapping (VLSM): sample

maps

Fluency Comprehension

Bates, Wilson, Saygin, Dick, Sereno, Knight & Dronkers, 2002

Basal Temporal Language Area

Reading Area: Angular Gyrus

“Broca’s Area”: PIFG “Wernicke’s area”: PT/IP

Disruption model of language function

Frontal regions44 inf 44/6 9/6 Exners area4645476 medialTemporal regions41/422221/2037Parietal: 40 39

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Basal Temporal Language Area

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• Mills Naming Center; Nielson’s language formulation center• Involved in object naming• Lesion: Pure anomic aphasia• Category specificity in more anterior areas• Believe pathways project ant/sup through insula

BTLA is difficult to image:

• Major artifacts; need to indicate where you haven’t signal- false negative risk

• Object naming area: verb generation is NOT a good activator of this region

Wernicke’s area(s)• Inferior portion: middle temporal

gyrus/superior temporal sulcus– Often bilateral activation

• Superior portion: superior temporal gyrus/supramarginal gyrus– Posterior/adjacent to TTG

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Wernicke’s area(s)• Critical for auditory language comprehension; word

recognition, sequencing phonemes• Lesions: grammatic speech; multiple paraphasias; • Superior lesions: phoneme selection deficits, sequencing

deficits; reading problems• Activations often quite deep in sulci• Output travels posterior and superior in arcuate fasciculus• Lesions of white matter tracts into and out of the region can

lead to serious deficits;These can be quite distal to the cortical processing areas

• Object naming, word generation --poor activators

Arcuate fasciculushttp://da.biostr.washington.edu/da.html

Frontal language areas

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Bookheimer 2003 Annual Rev. Neurosci.

Orbital frontal cortex: 47/45• Arguments about its job: semantics;

verbal selection; selection generally• Integration of (semantic) information• Lesion/electrical stimulation: semantic

integration deficits: normal object naming, grammatic speech; impaired auditory responsive naming

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“Broca’s” area: 44 and 45• Superior to IFS/PCS border, inferior to sylvian• Focal region; variable in precise location; some

language specificity• Must exist! • Lesions: grammatic output; naming; generation;

phoneme monitoring; syntax comprehension; effortful speech; arrest or anomia with stimulation

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A B

Phonology in IFGGelfand and Bookheimer, Neuron 2002

reverse

delete

match

Exner’s Area

• 6/8 in MFG/PMC

• Associated with pure agraphia

• Appears in many tasks

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Longcamp et al NeuroImage 2003

Matsuo et al Neurosci Lett 2003Exner’s area vs FEFPhoneme to grapheme task; saccades

FEF Exner’s

Stimulated region

Tumor

Stimulated region

Angular Gyrus

• Critical for reading

• Integrates auditory and visual information

• Pathways from IT to AG, oCC-AG, AG-SMG, all vulnerable

Reading phrases

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Supplementary Speech Area (Pre-SMA, Speech SMA)

• Important in initiating a motor speech plan• When removed, get a complete arrest of speech;

lesions may reduce initiation or lead to a “dwindling aphasia”; comprehension is normal

• Easily reorganizes to intact RH when the callosum is intact- 1-3 weeks

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Anterior Insula• Very often bilaterally symmetric• When lesioned bilaterally (and selectively):

pure apraxia of speech• Lesions of area (nearby white matter, IFG,

striatum) lead to profound expressive aphasia• Do not use to establish laterality; don’t

recommend to remove it either

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Dorsolateral Pre-frontal Cortex

• Not a language area• Will show activation, sometimes

unilateral, especially on generation tasks• Lesions show reduced fluency;

stimulation often produces perseverations• Don’t use for laterality; often removed in

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Language 2

• Reading system and reading disorders

• Right hemisphere contributions to language– Prosody– context

Reading System

• Major issue in reading: 1 or 2 pathways

• Call this the Dual Route model

• Was controversial before functional imaging- now its pretty well accepted

• Based on differences in acquired alexia errors

Types of Alexia

• Phonologica, literal or Surface– Patients read in a letter-by-letter fashion– They sound out each word– Errors: they can read pronounceable

nonsense words “migbus”; cannot read irregular words like “yacht”

– Damage likely to the visual recognition system in the LH: cant recognize whole words

Alexia cont.

• Alexia type 2: visual, semantic alexia– Can read whole words– Can read irregulars like yacht and pharoah– Cannot read nonsense words– Strong frequency effect- more likely to read common than

uncommon words; better at concrete nouns– Make visual or regularization errors: lit = light; groal=goal,

etc.– Apparently have damage to phonological to orthographic

conversion system or to phonological system

Rarer alexias

• Global alexia: affects all reading. AG lesions or WM exiting visual cortex in LH

• Deep dyslexia: associated with large LH lesions- characterized by global dyslexia with:– Visual errors: gird=“girl”– Derivational errors: architecture= architect– Semantic errors: orchestra=symphony– Superior at reading concrete nouns– Suggested to represent some primitive RH whole word

recognition capabilities

Rarer alexias, cont.

• Alexia without agraphia or occipital alexia:– Most other acquired alexics have impaired writing similar to

reading– Alexia without agraphia associated with 2 lesions: one in the

left occipital cortex and one in the posterior callosum– Disruption of visual information into the LH reading system.

Usually accompanied by a field or quadrant cut– Can write, but cant read what they write

Developmental dyslexia

• Most are similar to the surface alexic– Difficulty with auditory processing– Poor at grapheme to phoneme conversion– Lousy at reading nonwords– Slow readers; often learn by whole-word

approach

• Rarer, there are visual types and often some with general language difficulties

Temporal/OccipitalJunction 21/20/37

Superior TemporalGyrus (posterior)42,41;22

Angular Gyrus (39)

Supramarginal Gyrus (40)

Inferior FrontalGyrus

Anatomy of Reading

Dual Routes

• Inferior Route:– Occipital V1-V2-V3-IT-insula/44/47

• Superior Route– V1-V2- AG-ST- IFG 44/6

• Interaction through AG• Writing: includes SMG and Exner’s area

(46/6 anterior to M1 hand)

Right hemisphere contributions to language

• Some evidence that early right brain lesions can be more detrimental to language development than LH lesions

• LH may process more rapid information. RH may maintain a context and provide emotional cues to global meaning

• Some evidence that the ear itself is tuned for more rapid auditory information in LH or infants (Sininger 2004 Science).

Prosody Paradigm

• Selective attention/stimulus matched paradigm

• For the 2 prosody conditions: – “Do the sentences sound alike” regardless

of literal meaning

• For the SC condition:– “Do the sentences mean the same thing”

regardless of the sound

Affective prosody vs. others

Linguistic vs. Affective

Linguistic Prosody- Left Affective Prosody- Right

Making Sense of Conversation(R. Caplan and M. Dapretto, 2003)

• Logical Reasoning– Q: Do you like having fun? – A: Yes, because it makes me happy.

• Illogical– Q: Do you like having fun?

– A: No, because it makes me happy. •On-topic

–Q: Do you believe in angels?–A: Yeh, I have my own special angel

•Off-topic (LA)–Q: Do you believe in angels?–A: Yeh, I like to go to camp

Reasoning vs Topic

Normal Adults

Topic vs Reasoning in Normal Adults

Reorganized language in early lesions

• Can see individual patterns using fMRI

• Appears to follow a principle of minimal energetics: only move what is essential to move

Initiates speech on the right; language is on the left

Auditory Naming Task

Patient: LH tumor; R handed, R Brain Speech, Wada confirmed

Rasmussen’s Disease, age 12

LeftRight

Six months post left hemispherectomy

Right hemisphere contributions to language

• Sentence level: Topic maintenance vs logical reasoning

• Understanding metaphor, purpose or intent of speaker

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