Psychology 393
Cognitive Neurology
Language and Aphasia
March 06, 2007
Today’s Lecture
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Understanding Aphasia
Classic Views of Aphasia
Psycholinguistics and Aphasia
Alexia & Dual-Routes to Reading
Agraphia
Aphasia Definition
• Loss of language processing ability after
brain damage.
• It is not…
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An impairment of intellectual functioning
A psychiatric disturbance
A primary motor or sensory deficit
A developmental disorder
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Classic Syndromes: History
Broca (1861/1865)
• Localization of the faculty of articulate
speech
• Posterior portion of the inferior frontal
convolution of the left hemisphere
Classic Syndromes: Broca’s
Aphasia
• Major disturbance in speech production
• May retain use of nouns & verbs
• Loss of pronouns, articles, conjunctions
(“telegraphic”)
• Demonstrate ++ effort
• Comprehension intact
• AKA non-fluent,
expressive aphasia
Classic Syndromes: Broca’s
Aphasia
• Example:
Yes ... ah ... Monday ... er Dad and Peter H
…Frank (his own name), and Dad ... er
hospital ... and ah ... Wednesday ...
Wednesday nine o'clock ... and oh ...
Thursday ... ten o'clock, ah doctors ... two
... an' doctors ... and er ... teeth ... yah.
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Classic Syndromes: History
Wernicke (1874)
• Localization of the ‘storehouse of auditory word
forms’
• Posterior portion of the first temporal gyrus
• First description of an aphasic syndrome
– Fluent paraphasic speech and poor comprehension
– Linked to a single functional abnormality: “abnormal
representation of the sound pattern of words”
(Caplan, 2003).
Classic Syndromes: Wernicke’s
Aphasia
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Major disturbance of auditory comprehension
Fluent speech
Normal rate, rhythm, intonation
Disturbances of sounds, structures of words
Semantic paraphrasias
Poor repetition, naming
AKA fluent, receptive
aphasia
Classic Syndromes: Wernicke’s
Aphasia
• Example:
Well this is .... mother is away here working
her work out o'here to get her better, but
when she's looking, the two boys looking
in other part. One their small tile into her
time here. She's working another time
because she's getting, too.
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Classic Syndromes: History
• Wernicke:
– Disconnection of Wernicke’s and
Broca’s areas
– “sound images received by Wernicke’s
area could not be conducted forward to
Broca’s area to be produced”
– Results in failure to repeat
Classic Syndromes: Conduction
Aphasia
• Failure to repeat
• Paraphasias (phonemic)
• Disconnection syndrome: disruption of arcuate
fasciculus (tract between Broca’s and
Wernicke’s)
Classic Syndromes: History
Three principles underlying classic aphasic
syndromes (Caplan, 2003):
• Localization of language processors
• Damage to single processor can = multiple
deficits
• Language processors localized because of
relationship to primary sensory/motor
functions
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Classic Syndromes: History
Lichtheim (1885)
• Localization of the store of word
meanings, i.e. the ‘concept center’
• Meanings of words resided in superior
portion of the parietal lobe.
• Described 7 syndromes
Classic Syndromes: Lichtheim’s Model
‘Concept Center’
‘Articulate speech’
Motor area
C
M
‘Auditory word forms’
Auditory area
A
Primary
motor area
Primary
sensory area
PM
PS
Classic Syndromes: Lichtheim’s Model
Reduced fluency
of speaking,
reading, repeating
without severe
disturbance of
comprehension
C
Broca (nonfluent) Aphasia
M
A
PM
PS
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Classic Syndromes: Lichtheim’s Model
Fluent speech with
paraphasias &
impaired auditory
comprehension
C
Wernicke (fluent)
Aphasia
M
A
PM
PS
Classic Syndromes: Lichtheim’s Model
Disturbance of
spontaneous
speech &
repetition, no
disturbance in
comprehension
C
M
A
Conduction
Aphasia
PM
PS
Classic Syndromes: Lichtheim’s Model
Comprehension
disturbance
without
disturbance of
repetition
C
Transcortical
Sensory Aphasia
M
A
PM
PS
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Classic Syndromes: Lichtheim’s Model
Transcortical
Motor Aphasia
Spontaneous
speech reduced
but repetition
intact
C
M
A
PM
PS
Classic Syndromes: Lichtheim’s Model
Transcortical
Motor Aphasia
Broca
Aphasia
C
M
Transcortical
Sensory Aphasia
A
Wernicke
Aphasia
Conduction
Aphasia
PM
PS
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Classic Syndromes:
Neuroanatomy
Classic Syndromes: Neuroanatomy
Classic Syndromes: Limitations
• Incomplete or unsystematic
• Poor classification of aphasic patients
– Patients with the same syndrome could have different
deficits
– Patients classified into different syndromes can have
similar deficits (e.g. anomia - naming problems).
• Syndromes are not well correlated with lesion
location.
• Limited utility in assisting with treatment planning.
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Classic Syndromes: Limitations
Psycholinguistic Approach
• Language not broken down into production
and comprehension
• Recognizes more levels of language
– Single words (lexical)
– Word morphology (words formed from other words, e.g.
agree
agreement
– Formation of sentences, syntax, intonation
– Generation of discourse, meaning
Psycholinguistic Approach
• Emphasizes specific language processing
operations
– Phonology
– Syntax
– Semantics
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Psycholinguistic Approach: Phonology
• Phonology: sounds that compose a language and rules
that govern their combination.
• Two ways to represent sound in speech:
– Phonemic: smallest unit of sound that can signal
meaning (e.g., /b/ in /bat/ and /p/ in /pat/); allophones
are different representations of the same phoneme
(e.g., /p/ in /pill/ vs. /spill/)
– Phonetic: how phonemes are produced in different
contexts (i.e. selection of correct allophone)
Psycholinguistic Approach: Phonology
• Phonological processing can be disrupted in 2 ways
– disruption of phonetic representations (nonfluent aphasia)
– Phoneme substitution and difficulty with phoneme discrimination
(fluent & nonfluent)
• Broca’s aphasia = poor phonetic ability and phonemic
selection/discrimination
• Wernicke’s aphasia = poor phonemic
selection/discrimination BUT preserved phonetic ability
Psycholinguistic Approach: Syntax
• Syntactic structures: provide the means through
which meanings of individual words are combined
with one another to represent propositional
meaning:
– Verb endings (‘ing’, ‘ed’)
– Prepositions (‘by’, ‘to’)
• Remember: Broca’s aphasia patients produce
telegraphic speech…
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Psycholinguistic Approach: Syntax
• Anterior lesions (i.e. Broca’s-type aphasia) have been
commonly associated with deficits in syntactic production:
– Few function words and affixes are produced
– Greater retention of content words (telegraphic speech)
– Evident in spontaneous speech, repetition and writing.
• These lesions are also associated with comprehension
deficits…
• Agrammatic aphasia – aphasic syndrome denoting
syntactic deficits. Production and comprehension are
commonly impaired, although deficits are dissociable.
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Psycholinguistic Approach: Syntax
Study of syntactic comprehension in Broca’s
Aphasics (Caramazza & Zurif, 1976). Picture
matching….
The apple the boy is eating is red
OK
The boy the dog is patting is tall
POOR
The girl the boy is chasing is tall
POOR
The boy is eating a red apple
OK
Psycholinguistic Approach: Syntax
• Broca’s & Conduction aphasics only made errors
when selecting pictures representing sentence 2 &
3:
– syntax indicated an improbable event in the real world
or
– thematic roles of the subjects were reversible
• Early evidence for comprehension deficits in
Broca’s & conduction aphasia.
Psycholinguistic Approach: Syntax
• Competing theory: reduced ‘processing resources’
in aphasic patients – i.e. greater syntactic
complexity = greater aphasic deficits. Working
memory deficit?
“The boy who the girl who the woman hit kissed
slipped”
“The woman hit the girl who kissed the boy who
slipped”
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Psycholinguistic Approach:
Lexical/Semantic
• Lexical-semantic system:
– component of the language system dealing with
words and their meaning (i.e. outside the
context of a sentence).
• Lexical = form; Semantic = meaning
Psycholinguistic Approach:
Lexical/Semantic
• Double dissociation of lexical and semantic
representations of words:
– Intact semantic knowledge, impaired naming = ‘Tipof-the-tongue’ & anomic deficits
– Intact naming with impaired semantics = temporal
lobe atrophy (semantic dementia).
• Suggests meanings represented separately from
forms
Psycholinguistic Approach:
Lexical/Semantic deficits
• Semantic processing relatively spared in anterior
lesioned aphasic patients. Access to meaning more
commonly disrupted by posterior lesions
Point to the yellow square and then the blue circle
• In anterior aphasics, responding to commands is
preserved unless proper meaning is reliant upon
syntactic comprehension.
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Classical vs. Psycholinguistic Approach
General Conclusions
Classical characterization of aphasic deficits:
• Anterior = poor speech production
• Posterior = poor speech comprehension
Dissociation: comprehension vs. production
Psycholinguistic characterization:
• Anterior = syntactic processing
• Posterior = semantic processing
Dissociation: syntax vs. semantics
Resolution?…Converging
Evidence
• Converging Evidence: imaging studies
– Evidence of anterior/posterior dissociations
– Cortical basis much broader than originally thought
– More support for
cortical organization
based on psycholinguistic
Sy
Ph
model (phonology, syntax,
Se
Se
& semantics) than
Ph
traditional models
of speaking, repeating,
listening
Alexia / Acquired Dyslexia
• Alexia = loss of reading ability due to brain damage
• Dejerine (1891)
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Patient with infarct of L parietal lobe
poor reading and writing ability
Alexia with agraphia
Interpretation: Disturbance to the ‘optical images for
words’
• Dejerine (1892)
– Another patient with L parietal infarct
– Poor reading with preserved writing
– Alexia without agraphia (i.e. pure alexia)
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Alexia: Dual-Route to Reading
• Words may be identified by:
– Lexical procedure: letter strings matched to an entry
in a stored catalogue of words (visual form system)
– Phonological procedure: letter string converted
directly to phonological form through application of a
set of learned correspondences between orthography
& phonology
• Forms basis of surface vs. deep dyslexia
distinction
Alexia: Dual-Routes to Reading
Print to sound
conversion
B
Written word
B
Speech
Visual Analysis
A. Lexical pathway
B. Phonological (Non
lexical, grapheme
to phoneme)
pathway
Visual Word
Form System
A
Phonological
Output Lexicon
Cognitive System
Alexia: Dual-Routes to Reading
• Patient J. C. (Marshall & Newcombe,
1973) :
– Rarely applied the “rule of e” (e.g. read “like”
as “lik”)
– Great difficulty pronouncing consonant
clusters, vowel digraphs
– Diagnosis: surface dyslexia (surface alexia in
Banich)
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Alexia: Dual-Routes to Reading
• Surface Alexia
– Read by sound, using grapheme-to-phoneme
relatins
– No difficulty with regular words and non-words
– Difficulty with irregular words (e.g. yacht)
– Associated with temporal lobe atrophy
Alexia: Dual-Routes to Reading
• Patient G. R. (Marshall & Newcombe,
1973) :
– Able to read approximately 50% of concrete
nouns (e.g. table, apple)
– Unable to read abstract nouns (e.g. destiny,
truth)
– Errors semantically related to target word—
semantic paralexias (e.g. read “speak” as
“talk)
– Diagnosis: deep dyslexia (called deep alexia
in Banich)
Alexia: Dual-Routes to Reading
• Deep Alexia
– Semantic errors (related to target word)
– Influence of “imageability” of word: more
difficulty with abstract words
– Better with nouns than verbs (function words)
– Visual errors (e.g. skate for scale)
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Alexia: Dual-Routes to Reading
• Phonological Alexia
– Possibly milder form of deep alexia
– Deficit in process of translation of print to
sound
– Preserved reading of previously learned
regular and irregular words
– Poor non-word reading
– Associated with lesions to superior temporal
lobe, supramarginal gyrus, angular gyrus
Alexia: Dual-Routes to Reading
• Damage to Phonological Pathway
– Phonological alexia
• Damage to Direct (Lexical) Pathway
– Surface alexia
• Damage to both pathways
– Deep Alexia
Alexia: Dual-Routes to Reading
Print to sound
conversion
B
Written word
Damage to B:
phonological
dyslexia
Damage to A & B:
deep dyslexia
Speech
Visual Analysis
Damage to A: surface
dyslexia
B
Visual Word
Form System
A
Phonological
Output Lexicon
Cognitive System
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Alexia / Acquired Dyslexia
Peripheral vs. Central Alexias (Shallice &
Warrington, 1980)
Peripheral Alexias:
• Deficit in the processing of visual aspects of
the stimulus
• Prevents matching of familiar words to visual
word form
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Alexia: Peripheral Alexias
Print to sound
conversion
B
Written word
B
X
Speech
Visual Analysis
Visual Word
Form System
A
Phonological
Output Lexicon
Cognitive System
Alexia: Peripheral Alexias
• Alexia without agraphia
– Disconnect of RH visual system from LH wordrecognition system
– Damage to corpus callosum
• Neglect dyslexia
– Failure to explicitly identify initial portion of a letter
string (e.g. ‘paramount’ read as ‘mount’
– Influenced by lexical status of stimuli (i.e. not a letter
recognition deficit – higher order neglect).
• Attentional dyslexia
– Impaired contextual reading (e.g. sentence reading)
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Agraphia
• Acquired disorders of writing
• Early distinction between…
– Amnemonic = well-formed, but incorrect letters
– Atactic = poorly formed but correct letters
• Classical models linked agraphic deficits to
aphasic syndromes (e.g. fluent vs. nonfluent)
Agraphia
Phonological agraphia
• Loss of ability to spell nonsense words.
• Preserved ability to spell real words (regular and
irregular)
Lexical Agraphia
• Impaired ability to spell irregular words
• Preserved ability to spell regular real and
nonsense words
Semantic Agraphia
• Semantic substitutions (i.e. ‘knight’ for ‘night’).
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