Aphasia

• Loss or impairment of language comprehension or production

Language ImpairmentsPRODUCTIONSpontaneous Speech • Fluent versus nonfluent• Unintended or “off” words

(paraphasias)• Word finding difficulties

(anomia)• Poor articulation• Prosody (aprosodia)

RepetitionSingle wordsPhrases

Writing (agraphia)

COMPREHENSIONAuditory Single words Phrases Commands (Token Test) Syntax

Visual (Reading - alexia) Single words Phrases

Broca’s Aphasia

• Bouillaud (1825): large series of speech loss with frontal lesions

• Marc Dax (1836): LH damage, right hemiplegia, & aphasia linked

• Paul Broca (1861) convincing evidence of speech laterality; Tan “Nous parlons avez l’hemispheregauche”

Paul Broca (1824-1880)

Wernicke’s Aphasia

Carl Wernicke (1874) reports that temporal lobe lesion disturbs comprehension.

Developed connectionism model of language and predicated conduction aphasia

Aphasias

• Conduction– Fluent speech– Good comprehension– Poor repetition– Poor naming

• Possibly lesion in arcuate fasciculus or its connections in inferior parietal lobule

• Wernicke’s – Fluent speech– Poor comprehension– Poor repetition– Poor naming

• Posterior superior temporal lobe lesion (first temporal gyrus)

Aphasias

• Transcortical Sensory– Fluent speech– Poor comprehension– Good repetition– Poor naming

• Lesion in posterior temporo-parietooccipital junction while sparing Wernicke’s area

• Anomic– Fluent speech– Good comprehension– Good repetition– Poor naming

• Temporal or temporo-parietal lesion

Wernicke & TCS Aphasia

Aphasias

• Broca’s – Non-fluent speech– Good comprehension – Poor repetition– Poor naming

• Posterior inferior frontal lesion

• Global – Non-fluent speech– Poor comprehension– Poor repetition– Poor naming

• Lesion involves frontal, temporal and parietal lobes, Including Broca’s and Wernicke’s area

Aphasias

• Mixed Transcortical– Non-fluent speech– Poor comprehension– Good repetition– Poor naming

• Anterior and posterior association cortex lesions while sparing perisylvian language region

• Transcortical Motor – Non-fluent speech– Good comprehension– Good repetition– Poor naming

• Lesion involves frontal lobe but spares Broca’s area

Linguistic processes

Turn of the century models for Reading and Speaking

Reading Aloud(Grapheme to Phoneme conversion – GPC)

TOKEN TEST: Point to the large yellow circle

Linguistic Competence of the Disconnected RH

Vocabulary vs syntactical competence

Lexical Language in the disconnected RH

-?+NG

-?+LB

GPCSyntacticalAuditory Compreh.

Reading Compreh.

Split Brain Patients

Token test assesses auditory comprehension but more so syntactical competence

Auditory comprehension GPC (via Rhyme)Reading

GPC

but may index visual familiarity)

Lexical Language in the disconnected RH

--+++NG

--+++LB

GPCSyntacticalAuditory Compreh.

Reading Compreh.

Split Brain Patients

Token test assesses auditory comprehension but more so syntactical competence

LH RH

Syntactical incompetence of the RH (poor prepositions) but competence for nouns and adjectives, with control for word frequency (i.e., visual familiarity)

Not all nouns are alikeRH competence for concrete and imageable

Concrete but not imageable• Encephalon• Matter• Welt• Imprint• Morass• plaza

Not Concrete but imageable• Alone• Affectionate• Wise• Joy• Fun• blessing

Right Hemisphere Ability

Lexical Language in the disconnected RH

-

-

GPC

-

-

Syntax

Concrete only

Concrete only

Nouns

-+++NG

-+++LB

Aud. Phonetics

Aud. Comp.

Read Comp.

Split Brain Patients

Isolation of grapho-motor module• In VJ, writing dissociates

from other language abilities.

– Writing in RH

– All others LH

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

Unusual brain organization - dissociations

Gross functions across split brain series

+--++NG

-++++PS

-

-

+

Writing

++++VP

--++RY, AA, DR, VJ

+?++LB, JW

SemanticsSpeechReading Compreh.

Auditory Compreh.

Split Brain Patients

Patient O.A.

Linguistic Competence that requires intact interhemispheric language systems

• Alternative meanings– Narrative processing, inference– Metaphor– Humor– Indirect request

Technique suitable for fast, short presentations only – <180 ms

inference

How to test sustained visual attention in one visual field: Z-lens

Ongoing inference in sentential readings

The pizza was too hot to cry

Hough (1990) - Narrative Integration

Polysemantic Processing• Revising interpretations of non-humorous discourse

Sally became too bored to finish the history book. She had already spent five years writing it. (or we saw her duck)

• Same initial inference generated by controls and RHD, but RHD failed to abandon dominant inference for alternative interpretation consistent with both sentences (Brownell 1996)

• RHD performance = normals’ for integrating across sentence boundaries.

Johnny missed the wild pitch.The windshield was shattered.

• Related Findings– RH maintains activation over longer prime-target intervals.– RH primed by weakly associated primes (foot, cry, glass for cut) as much as by

direct prime (scissors for cut). – LH shows only priming for direct prime

• Conclusions• RH generates extensive (multiple) representational sets for meanings implied or novel• LH inhibits alternatives and focuses on dominant reading.

– LH excels at selecting & processing one (dominant) interpretation.

Priming for Polysemy

• Dominant context: The dog played with the ball

• Subordinate context: She bought a new dress for the ball

Associated: ROUND (dominant) or DANCE (subordinate)

• By 40 ms LH (RVF) has collapsed all subordinate (alternative) word meanings or never allowed them to emerge

(I put my money in the bank)

Deep dyslexia

Deep dyslexia - Reliance on diffuse representational system of RH

New word learning shifts child’s attention from thematic (RH) to categorical (LH)

• RH = vocab 13y, syntax 5y

Aphasia with multiple languages

• Bilingual recovery– Parallel recovery– Differential or nonparallel recovery

• L1 recovers faster (“Ribot’s law”—old before new)• L2 recovers faster (“Pitres’ law”—frequent first)• Due to different or overlapping brain areas, or what?

• Recovery implies that actual language centers weren’t destroyed, only cut off or inhibited.

Recovery from aphasia

• L1 and L2 may recover independently– implies some differential representation in the brain.

• Case – L1 recovery only: Dimitrijevic (1940). • Woman grew up speaking Bulgarian & Yiddish (both L1),

As adult, she learned Serbian (L2) which she spoke daily for 25y. She kept “forgetting” Bulgarian until brain injury at 60y resulted in loss of Serbian in speech (however, she still could understand L2)

Second language recovery• 1/3rd of multilinguals do not recover L1, but L2 or L3

• Case L2 recovery: Minkowski (1928). • Acquisition:

– L1=Swiss German– L2 schooled in standard German – L3 became fluent in French, then stroke after 19 y

• Recovery: – spoke French (L3) for 3 weeks, then German (L2), but

incapable of using Swiss German (L1) for 6 months. – Suddenly L1 returned, to detriment of French (L3).

Factors involved in L2 recovery

• Minkowski: Languages are not spatially separated, but exert mutual inhibition in delicate balance (“Great Powers of Europe metaphor” 19-20th c).– Lesion disrupts balance and can suppress any language

(including L1).– In support, “lost” languages can be recovered faster than

usually required to “learn from scratch”– Little evidence of right hemisphere involvement in L2

• But Broca’s area in polyglots is no larger than monolinguals (e.g. Sauerwein spoke 54 languages with a normal-sized Broca’s area, Fabbro 2001)

Experimental inhibition(Ojemann & Whitaker 1978)

•Dutch inhibited•English inhibited•Both inhibited•Neither inhibited

Recovery of dead languages

• Case: Grasset (1884). Patient knew only French. After stroke, he could speak only single words in Latin that he learned from Mass.

• Case: Pötzl (1925). Classics professor suffered a stroke and was only able to express himself in dead languages (Latin & ancient Greek), which he acquired through reading alone.

Bilingual representation

– Sometimes only one language returns• not always L1

– Production, comprehension and translation separable, even within a language.

– Comprehension often spared in all languages– Inconsistent evidence for macroscopic localization

differences for multiple languages (VHS Mind # 26)

PET vs Lesion data

Why is PET data so much more focal?

Individual Differences in Language Lateralization

Agnosia

• Greek for “lack of knowledge”– Coined by Sigmund Freud

• Inability to recognize people or objects even when basic sensory modalities, such as vision, are intact.

• Modality-specific impairment

“What & Where” – Ventral and Dorsal Visual Pathways

• Established with electophysiology, lesion, neuropsychology and neuroimaging data

What-Where Distinction

Object task: Same objects?

Spatial Task”Same locations?

Three Types of Object in the World

Words – Objects – Faces Alexia – Agnosias – Prosopagnosia

• Recognition involved three (or four) stages of processing:

1. Sensory input

2. Perception (able to form percepts)

3. Categorization (able to associate percept to meaning)

4. Identification (able to identify specific example)

Agnosia

• Apperceptive– Object recognition failure due to perceptual

processing

• Associative– Perceptual processing intact but subject

cannot use information to recognize objects

Apperceptive Agnosia

Impaired global structure (gestalt) extraction

1. Diffuse brain injury (CO poisoning)2. Intact acuity, brightness discrimination,

color vision and other elementary capabilities

3. Real images recognized better than illustrations; motion better than static (more cues)

Gestalt Principles

Example of connectedness

Gestalt principles

Case D.F. Case D.F. (Milner & Goodale, 1995)(Milner & Goodale, 1995)

• Classic Apperceptive Agnosic

• Severly impaired FORM perception

• Damage to V2, V3, V4-- Ventral Stream

• Intact abilities should reflect operation of dorsal stream

Dissociating Dissociating WhatWhat from from HowHow

• Orientation reports: IMPAIRED– verbal

– matching

• Posting behavior SPARED

Implication: Orientation & shape representations available for guiding action

D.F. Control

Perceptualmatching

Visuomotorposting

Associative Agnosia

Impaired matching percept to memory

1. Occipitotemporal damage

2. Draw accurately without recognizing

3. Identify objects through other modalities (touch, verbal description)

4. Not perceptual except copying is slow and sequential

Prosopagnosia or Face Blindness

Prosopagnosia

• Specific inability to recognize faces

• Are faces and other objects in the world represented in fundamentally different ways in memory?

• Does face-memory depend on fundamentally different brain systems?

Are Faces Special?

Are Faces Special?

• Objects represented in parts and holistically• Faces represented holistically

Prosopagnosia

Impairment of identity of familiar faces

1. Posterior artery (medial OT, right sided usually)2. Perception and categorization is intact. Patient can still

determine gender, ethnicity, age, emotions, everything but identity

3. Conscious recognition impaired4. Nonconscious (implicit) recognition intact in some –

GSRs, EPs, forced decision5. Are faces a unique set of stimuli? Or difficult to

discriminate highly similar exemplars from each other (e.g., prosopagnosic farmer who couldn’t recognize faces but could recognize his cows)

ISSUE: Are faces and other objects in the world represented in fundamentally different ways in memory?

Single cell recording in IT

Other agnosias• Auditory Agnosia• inability to recognize specific sounds in the context of intact hearing.

– pure word deafness– sound agnosia– receptive amusia (agnosia for music).

• Somatosensory Agnosia (Astereognosis)• difficulty perceiving objects through tactile stimulation though basic

tactile sensation intact.

• Simultanagnosia, Inability to recognize a whole image although individual details are recognized.

• Color anomia can discriminate colors on tasks but cannot name colors or point to colors named by examiner. (color recognition problem, not color perception which is Central Achromatosia)

Alexia (with or w/o agraphia

Impairment in letter recognition and reading

1. OP damage

2. Word blindness – inability to read

Patterns of dissociation support this idea: