Ling 411 – 07
Brain Damage
and
Locations of Linguistic Functions
Why so much variation in symptoms?
 Difference in areas of brain damage
 Difference in kinds of brain damage
• Strokes vs trauma vs infection vs tumors
• Different kinds of stroke
 Anatomical variation among people
• Differing cortical structures
• Differences in vascular anatomy
 Difference in location of cortical functions
Why so much variation in symptoms?
 Difference in areas of brain damage
 Difference in kinds of brain damage
• Strokes vs trauma vs infection vs tumors
• Different kinds of stroke
 Anatomical variation among people
• Differing cortical structures
• Differences in vascular anatomy
 Difference in location of cortical functions
Different types of brain damage
 Strokes, wounds, tumors, infections, degenerative disease
 Each of these occurs in varying locations
 Each of these has varying extent of damage
Different Kinds of Stroke Damage
1. Ischemic: blockage of artery
• Two sources of blockage:
1. Thrombosis (about 2/3 of all ischemic
strokes) (B&A 64)
2. Embolism: caused by a blood clot, air
bubble, or detached clot
• Result: infarction – death of brain tissue
that is no longer receiving blood supply
• Variation in location of blockage
• Hence, variation in area of infarction
2. Hemorrhagic: bleeding into cerebral tissues
• Variation in location and extent of
hemorrhage
Stroke mechanisms
http://www.youtube.com/watch?v=M_fo6ytlmD0&feature=related
Why so much variation in symptoms?
 Difference in areas of brain damage
 Difference in kinds of brain damage
• Strokes vs trauma vs infection vs tumors
• Different kinds of stroke
 Anatomical variation among people
• Differing cortical structures
• Differences in vascular anatomy
 Difference in location of cortical functions
Cerebral Arteries
 Anterior Cerebral Artery
• Feeds frontal pole and most of the medial surface
 Middle Cerebral Artery
• Feeds most of cortex,
 Perisylvian area
 Other areas
 Posterior Cerebral Artery
• Feeds bottom of temporal lobe and medial
surface of occipital and parietal lobes
View of actual brain with arteries
http://www.youtube.com/watch?v=Qn4NArz385U&feature=related
Left hemisphere,
showing
middle
cerebral
artery
Middle Cerebral Artery (Right Hemisphere)
www.strokecenter.org/education/ais_vessels/ais049b.html
The middle cerebral artery is the largest branch of the internal carotid.
The artery supplies a portion of the frontal lobe and the lateral surface
of the temporal and parietal lobes, including the primary motor and
sensory areas of the face, throat, hand and arm and in the dominant
hemisphere, the areas for speech. The middle cerebral artery is the
artery most often occluded in stroke.
From Washington University Medical School
Middle
Cerebral
Artery
Inter-Subject
Variability
Aphasic syndromes and Cerebrovascular areas
 Territory
 Aphasic syndrome
• Anterior cerebral
artery occlustion
Extrasylvian motor
aphasia
• Posterior cerebral
artery occlusion
Occipital alexia
• Middle cerebral artery
occlusion
Various major types of
aphasia (next slide)
Aphasias with middle cerebral artery occlusion
 Total artery occlusion
Global aphasia
 Orbitofrontal branch
Broca aphasia
 Rolandic branch
Broca aphasia, cortical dysarthria
 Anterior parietal branch
Conduction aphasia
 Posterior parietal branch
 Angular branch
Wernicke aphasia, extrasylvian
sensory aphasia
Anomia, extrasylvian sensory aphasia
 Posterior temporal branch
Wernicke aphasia
 Anterior temporal branch
Anomia
Why so much variation in symptoms?
 Difference in areas of brain damage
 Difference in kinds of brain damage
• Strokes vs trauma vs infection vs tumors
• Different kinds of stroke
 Anatomical variation among people
• Differing cortical structures
• Differences in vascular anatomy
 Difference in location of cortical functions
Neuroanatomical correlates of the aphasias
Identifying linguistic functions
Locating linguistic functions
Evaluating evidence from aphasia
 It would be easy if naïve localization were true
• If a patient has lost an ability, then the area of damage
is the area responsible for that ability
 But naïve localization is false
 “… language, along with other complex cognitive
processes, depends on the concerted operation
of multicomponent, large-scale neural systems.
The anatomical components are often widely
dispersed and each acts as a partial contributor
to a complicated process…”
Antonio Damasio 1998:25
Simple Functions / Complex Functions
Complex
function
Simple
function
Suppose this area gets knocked out.
Then the whole complex function is impaired
Benson and Ardila on conduction aphasia
“… a single type of aphasia may have distinctly
different loci of pathology. Both conduction aphasia
and transcortical motor aphasia are examples of this
inconsistency.” (117)
(See also p. 135)
Hannah Damasio on conduction aphasia
“Conduction aphasia is associated with left perisylvian lesions
involving the primary auditory cortex…, a portion of the
surrounding association cortex…, and to a variable degree the
insula and its subcortical white matter as well as the
supramarginal gyrus (area 40). Not all of these regions need to
be damaged in order to produce this type of aphasia. In some
cases without involvement of auditory and insular regions, the
compromise of area 40 is extensive…. In others, the
supramarginal gyrus may be completely spared and the damage
limited to insula and auditory cortices … or even to the insula
alone….”
(1998: 47)
CT template – Conduction Aphasia (patient I)
CT template – Conduction Aphasia (patient II)
Left
auditory
cortex
and
insula
MR template – Wernicke Aphasia (patient I)
Posterior
portion
of
superior and
middle
temporal
gyri
MR template – Wernicke Aphasia (patient II)
Superior
temporal
gyrus,
AG,
SMG
CT template – Broca Aphasia (patient I)
Superior
sector of
Broca’s
area and
the premotor
region
immediately
above it
MR template – Broca Aphasia (patient II)
Most of
Broca’s
area,
motor
and premotor
regions,
white
matter,
insula
MR template – Transcortical Motor Aphasia
Motor
and
premotor
cortices
just
above
Broca’s
area
Two different patients with anomia
Inability to retrieve words
for unique entities
Deficit in retrieval
of animal names
(Left temporal lobectomy)
(Damage from stroke)
Two more patients with anomia
Deficit in retrieval of
words for man-made
manipulable objects
(Damage from stroke)
Severe deficit in retrieval of
words for concrete entities
(Herpes simplex encephalitis)
More on these four anomic patients
 “…anomic aphasia requires damage to left temporal
cortices located outside the traditional aphasia-producing
territories”
(Hannah Damasio 1998:50)
 All of these four subjects demonstrated normal concept
retrieval for the concrete entities they could not name
(Hannah Damasio 1998:51)
(But she does not elaborate – maybe it’s not really “normal” –
possibly RH conceptual knowledge?)
Don’t forget this – (repeating)
 Some information is bilaterally represented
• Highly entrenched items
• Initial consonants of high-frequency words (?)
• Some people have more bilateral
representation than others
• Women and left-handers tend to have more
bilateral representation than men and righties
 Semantic information is in both LH and RH
• But different aspects of semantic information
 Metaphor, irony, sarcasm, pragmatic features,
inferencing, subserved by RH
Conceptual category dissociation I
(from Rapp & Caramazza 1995)




J.B.R. and S.B.Y. (905b-906a)
Herpes simplex encephalitis
Both temporal lobes affected
Could not define animate objects
• ostrich, snail, wasp, duck, holly
 Much better at defining inanimate objects
• tent, briefcase, compass, wheelbarrow,
submarine, umbrella
 How to explain?
Conceptual category dissociation II
 J.J. and P.S. (Hillis & Caramazza 1991) (906-7)
• J.J. – left temporal, basal ganglia (CVA)
 Selective preservation of animal concepts
• P.S. – mostly left temporal (injury)
 Selective impairment of animate category
P.S
J.J.
MR template – Transcortical Sensory Aphasia
AG
and
posterior
SMG
Transcortical sensory aphasia
(A. Damasio 1998:36)
 Fluent and paraphasic speech
• Global paraphasias
 Severe impairment in oral comprehension
 Repetition intact (unlike Wernicke’s aphasics)
 N.b.: Refers to H. Damasio, Chapter 3, for localization of
damage
Brain damage and nominal concepts
 Access to nominal concepts is impaired in
extra-sylvian sensory aphasia
 Type I – Damage to temporal-parietaloccipital junction area
• I.e., lower angular gyrus and upper area 37
• Poor comprehension
• Naming strongly impaired
• Semantic paraphasia
 Type II – Damage to upper angular gyrus
• Variable ability to comprehend speech
• Naming strongly impaired
• Few semantic paraphasias
• Many circumlocutions
Benson & Ardila 1996
Summary: Correlations of symptoms
with areas of lesion
Aphasic Syndrome
Area of Damage
Broca’s
Broca’s area
Wernicke’s
Wernicke’s area
Conduction
SMG, Insula,
Arcuate fasciculus
Transcortical motor
Areas anterior and/or
superior to Broca’s area
Transcortical sensory
Areas posterior and/or
superior to Wernickes a.
Cf. H. Damasio 1998: 43-44
Correlation of aphasia types to localization of damage
“More than 100 years of study of anatomoclinical
correlations, with autopsy material as well as CT
and MR scans, has proven that in spite of the
inevitable individual variability, the correlation
between aphasia types and locus of cerebral
damage is surprisingly consistent.”
Hannah Damasio 1998: 64
Correlation of linguistic functions
to localization of aphasic damage
“…the correlations per se provide only limited
information about the neurobiological mechanisms
of language, in health and in disease.”
Hannah Damasio 1998: 64-6
Reasoning from brain damage to localization
 If area A is damaged and patient has deficit D of some
function F
 Does this mean that function F is subserved by area
A?
 Not really..
 It means that A (or some portion of A) is needed for
some component of F
Brain damage and localization of function
Hypothetical example
A function
Damage
Reading and Writing
Alexia and Agraphia
 Alexia with agraphia
• Reading and writing both impaired
• A rare disorder
 Patients with both impairments usually also have
Wernicke’s aphasia or transcortical sensory aphasia
 Alexia without agraphia, a.k.a. pure alexia
• Reading impaired, writing okay
• Can write spontaneously or to dictation
• Some can copy writing but with difficulty
Misprint in Antonio Damasio Reading
 Antonio Damasio, Signs of Aphasia
 P. 38: “As the designation implies, patients
presenting alexia with agraphia become unable to
read while they continue to be able to write…”
 Should be “…alexia without agraphia…”
More on patient J.G.
 Damage: Left posterior temporal-parietal
 Meaning spared, phonological recognition
okay, but couldn’t spell the word correctly
• digit:
 D-I-D-G-E-T
 “A number”
• thief:
 T-H-E-F-E
 “A person who takes things”
 These spellings are not correct, but..
Rapp & Caramazza 1995
Reading – relating writing to speech
Phonological
word image
Phonemes
The “Phonics” route
Letters
Reading – relating writing to speech
Phonological
word image
Graphic
word image
The “whole word” route
Letters
Two pathways for relating writing to speech
Phonological
word image
Graphic
word image
Phonemes
Letters
Redundancy?
Two pathways for relating writing to speech
 The “whole word” route is necessary for
• caught
• island
• sign
 The “phonics” route is needed for long unfamiliar words
• commissurectomy
• prosopagnosia
• magnetoencephalography
The spelling attempts of J.G.
(one more look)
 digit:
• D-I-D-G-E-T
• “A number”
 thief:
• T-H-E-F-E
• “A person who takes things”
 J.G. has damaged “whole word” route
but intact “phonics” route
 Evidence that the two routes are
separately represented in the cortex
More evidence on phonological and graphic forms
 Patient P.W. (905)
• Damage: anterior parietal & posterior frontal
• Tested on identifying spoken words
 [skirt]: “S-O-C-K, skirt”
• Verbal paraphasia in spelling but not in speech
 [brush]: “B-R-U-S-H, comb”
• Verbal paraphasia in speech but not in spelling
 [knife]: “S-P-O-O-N, fork”
• Verbal paraphasia in both modalities
 The paraphasias are semantically related
Connecting graphic representation to meaning
 The traditional view: speech is primary, writing secondary
• History
• Development
 Might suggest that writing has access to meaning only via
phonological representation
 But evidence from brain damage indicates that (at least
some) written forms have direct access to meaning,
independently of phonology
Pathway to meaning
Conceptual
information
Phonological
word image
Graphic
word image
Phonemes
Letters
Patient D.R.B. (Rapp &Caramazza 1995: 902b-903a)
 Left middle cerebral artery infarct
 Able to discriminate words and pseudo-words
• Either visual or auditory input
 Test: Two words – synonyms or not?
• For written input, 95% accurate
• For spoken input, only 61% accurate
 Evidence that representations of written words can
have direct connections to semantic information
Two pathways to meaning
Conceptual
information
Another pathway
Phonological
word image
Graphic
word image
Phonemes
Letters
Evidence for direct connections between meaning
and graphic form
 Patient D.R.B. (above)
• Judgments of synonymy better for pairs of
written words than pairs of spoken words
 Patient R.G.B (next slide)
 Patient H.W. (904)
Evidence for direct connections between meaning
and graphic form – Patient R.G.B. (R&C 1995: 904)
 Damage: left fronto-parietal
 Tested on identifying written words
 Semantic errors in spoken output
• Records (written form)
 Spoken response: “radio”
• Wrong but semantically related
 But gets the meaning: “You play ‘em on a
phonograph … can also mean notes you take and
keep”
 Assessment: Gets the meaning from written input,
but has impaired phonological information or
impaired connection to phonological information
Evidence for direct connections between meaning
and graphic form – Patient H.W. (R&C 1995: 904)
 Damage: left parietal and occipital
 Tested on identifying written words
• Interest:
 “bank” (spoken response)
• Wrong but semantically related
 “You go to the bank and put it in
and you get more money … not
very much now”
• Indicates that the meaning was
correctly accessed
Phonological-Graphic Connections:
The Angular Gyrus
The angular gyrus and the white matter below it appear
to be uniquely important for all aspects of graphic language
that involve its linkage to writing, to spoken language, and
to word meaning. Injury to this area disrupts not only the
ability to understand the written word, but also disrupts
related knowledge such as oral spelling and letter-sound
correspondence, and therefore disrupts the ability to write.
Harold Goodglass
Understanding Aphasia 1993:51
The angular gyrus
Angular
gyrus
Connecting to spoken output
Phonological
word image
Graphic
word image
Phonological
production
Phonemes
Letters
Broca’s area
Arcuate fasciculus
Wernicke’s area
Angular gyrus
Connecting to Spoken and Written Output
Exner’s area
Graphic
production
Superior longitudinal fasciculus
Phonological
word image
Graphic
word image
Phonological
production
Phoneme
images
Broca’s area
Arcuate fasciculus
Wernicke’s area
Letter
images
Angular gyrus
Exner’s Area
Broca’s
area
Wernicke’s area
Angular gyrus
end