Language and the brain What is the brain? Korbinian Brodmann

Language and the brain
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Language & The Brain
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What is the brain?
What is the brain?
What is language?: The neurological perspective
The classical language areas
u Wernicke’s area
u Broca’s area
u A typology of aphasia
What about syntax?
What (or how) does it all mean?: A word on semantics
The role of the right hemisphere
Humans have relatively huge amounts of association cortex.
Adapted from: W. Penfield (1975)
The Mystery Of The Mind
Korbinian Brodmann
(1868-1918)
What is the brain?
What is the brain?
What is language?:
The neurological perspective
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44/45
Spoken Word
Auditory Analysis
Visual Analysis
Sub-word level
orthographicto-phonological
conversion
Auditory
Input
Buffer
Auditory
Input
Lexicon
Sub-word level
auditory-tophonologial
conversion
*
Phonological
Output
Buffer
Sub-word level
orthographicto-graphemic
conversion
Phonological
Output
Lexicon
Phonological
to auditory
conversion
PHONOLOGY
Graphemic
Output
Buffer
Sub-word level
phonological
to orthographic
conversion
Phonological
Output
Buffer
Writing
Speech
BUFFER
Visual Analysis
Sub-word level
orthographicto-phonological
conversion
CONVERTER
Orthographic
Input
Buffer
To *
Auditory
Input
Lexicon
Orthographic
Input
Lexicon
Sub-word level
auditory-tophonologial
conversion
*
Graphemic
Output
Lexicon
LEXICON
Written Word
Auditory Analysis
Auditory
Input
Buffer
Graphemic
to orthographic
conversion
Orthographic
Input
Lexicon
Cognitive System
Speech
Spoken Word
Orthographic
Input
Buffer
To *
Phonological
to auditory
conversion
INPUT
WHOLE WORD PATHWAY
SUBWORD PATHWAY
CONVERSION PATHWAY
FEEDBACK PATHWAY
Written Word
Graphemic
to orthographic
conversion
Sub-word level
orthographicto-graphemic
conversion
Phonological
Output
Lexicon
Graphemic
Output
Lexicon
Sub-word level
phonological
to orthographic
conversion
ORTHOGRAPHY
Graphemic
Output
Buffer
Writing
A model of single word processing: 14 ‘nodes’
Redrawn from Howard & Franklin (1988)
(after Morton, 1980)
A model of single word processing: 14 ‘nodes’
The structure of single word language access
The structure of single word language access
PHONOLOGY
ORTHOGRAPHY
X
RECEPTION
PRODUCTION
SUBWORD
X WHOLE WORD X
Reception
OUTPUT
ACCESS(RECOGNITION)
RECEPTION
STORAGE (RECALL)
PRODUCTION
Production
Reception
Subword
Whole
word
Subword
Production
Whole
word
Phonology
1
2
3
4
Orthography
5
6
7
8
Spoken
1
2
What is the brain?
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PRODUCTION
Broca’s & Wernicke’s areas
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RECEPTION
Paul Broca (1824-1880)
What is Broca’s aphasia?
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What is Broca’s aphasia?
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Example:
"I feel very well. My hearing, writing been doing well, things that I couldn't
hear from. In other words, I used to be able to work cigarettes I don't know
how...This year the last three years, or perhaps a little more, I don't know
how to do me any able to."
Also called motor, expressive, or nonfluent aphasia
Main characteristic: prominent deficit in production
u morphology and syntax are often also disrupted, with patients
tending to rely heavily on unaffixed word forms
u adjectives, articles, and adverbs are often eliminated altogether
= 'telegraphic speech'
Motor areas of the brain
Motor areas of the brain
Carl Wernicke (1848-1904)
Broca’s area
What is Wernicke’s aphasia?
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Primary Auditory Cortex
Also called sensory or fluent aphasia
Main characteristic: prominent deficits in comprehension
Sometimes disruption of visual input or written output
Speech production is normal: normal rate, prosody, rhythm
u however, production errors increase, especially phoneme &
syllabic repetition errors and neologisms (made up words):
known as 'word salad'
u production can sometimes become excessive: 'press of speech'
or 'logorrhea'
u speech can also become semantically empty: 'empty speech'
u example: When asked where he lived "I came there before here
and returned there."
Auditory areas of the brain
Wernicke’s
area
Sensory association areas
Wernicke’s
area
Sensory association areas
The arcuate fasciculus
The arcuate fasciculus
How language breaks down
Adapted from Lichtheim, 1885
How language breaks down
Conduction aphasia
- Predicted by Wernicke
X
X
Adapted from Lichtheim, 1885
X
- What would you expect?
Conduction aphasia
- perceptual word image
(Wernicke’s area) is cut off
from motor image (Broca’s
area)
- patient can comprehend and
produce but cannot connect
comprehension to production
= a total inability to repeat
words
X
Transcortical sensory aphasia
X
- Main feature: a deficit in accessing
(thinking about or remembering) the
meanings of words
- comprehension is therefore severely
impaired
- the patient can neither read nor write
and has major difficulty in word
finding
Transcortical motor aphasia
X
Transcortical sensory aphasia
- Main feature: a Broca’s-like
nonfluent aphasia- no creative
speech, and can usually utter only
few syllables
- writing is usually impaired too
- difference from Broca's aphasics:
can repeat words and phrases
X
= disconnection of Wernicke's area
from its route through parietal
association areas
What would you expect?
Transcortical motor aphasia
X
= disconnection of Broca’s area
from its route through frontal premotor areas
What would you expect?
Mixed Transcortical aphasia
X X
What would you expect?
Mixed Transcortical aphasia
X X
- Also called ‘isolation of the
speech area’
- patients have no language
functions at all- cannot understand
or produce speech spontaneously
- however, they can repeat words
and characteristically do = echolalia
Mixed Transcortical aphasia
X X
- Also called ‘isolation of the
speech area’
- patients have no apparent
language functions at all- cannot
understand or produce speech
spontaneously
- however, they can repeat words
and characteristically do = echolalia
Question: How can we know that
their speech area is isolated and not
just gone?
Other aphasias
• Subcortical aphasia: lesions to basal ganglia (caudate nucleus and
putamen) or thalamus can cause transient aphasia similar to the
transcortical aphasias
• Global aphasia
• Anomic (or amnesic) aphasia
• Alexia
•Agraphia
•Word deafness
Other aphasias
• Subcortical aphasia
• Global aphasia
• Anomic (or amnesic) aphasia: With superior temporal damage,
fluent speech, no articulation disorders, good comprehension; wordfinding difficulties with failures (anomia) and errors (paraphasias)
• Alexia
•Agraphia
•Word deafness
Other aphasias
• Subcortical aphasia
• Global aphasia: multiple sites of damage, with laborious
articulation, poor comprehension, poor comprehension, poor repetition
• Anomic (or amnesic) aphasia
• Alexia without agraphia
•Agraphia
•Word deafness
Other aphasias
• Subcortical aphasia
• Global aphasia
• Anomic (or amnesic) aphasia
• Alexia: inability to read: damage is usually in temporal lobe, but
varying locations
•Agraphia
•Word deafness
Other aphasias
• Subcortical aphasia
• Global aphasia
• Anomic (or amnesic) aphasia
• Alexia without agraphia
•Agraphia: Inability to write: damage is usually in left supramarginal
gyrus (= inferior parietal lobe, just above Wernicke's area)
•Word deafness
Other aphasias
• Subcortical aphasia Global aphasia
• Anomic (or amnesic) aphasia
• Alexia without agraphia
•Agraphia
•Word deafness: With superior temporal damage, poor auditory
comprehension, repetition, but unimpaired production and reading
Why is aphasia so common?
1.) Because language-related tissue is ubiquitous
What about syntax?
2.) Because of the middle cerebral artery
What about syntax?
Zones where electrical stimulation produces
reading errors involving syntax
What about syntax?
- Morpho-syntactic deficits in patients differ by properties of the
language (highly versus weakly inflected)
- a bewildering variety of morphological dissociations have been
documented
- some patients have difficulty only when non-local operations
are involved
- some patients have difficulty with bound morphemes in
sentences, but not in isolation
- some patients are worse at inflectional morphology only
- some are much worse at compounding than inflections and
derivations
- some delete affixes, and some substitute them
- Libben (1990) reported a patient who produced repetition errors
only for nontransparent multimorphemic words (illegible, regularity),
not transparents (unhappiness, materialism)
What about semantics?
Humans have relatively huge frontal lobes.
Adapted from: T. Deacon (1997)
The Symbolic Species
What about the right hemisphere?
Humans are developmentally retarded (especially in their
prefrontal cortex and inferior parietal cortex)
Adapted from: J Eccles (1989)
Evolution Of The Brain
The corpus callosum
The ‘myth’ of lateralization
Asymmetries in
the planum temporale
- Left hemisphere = analytic, logical, local, and rational
- Right hemisphere = synthetic, Gestalt, holistic, global, and intuitive
- These characterizations do not adequately capture the phenomenon of
lateralization:
-The computations carried out within the right hemisphere require
the same degree of precision and difficulty as those in the left.
- Cerebral lateralization/ specialization is not a battle for dominance
between two competing processes, but a developmental streamlining of
complementary functions
Symptoms of right-hemisphere damage are wideranging and complex:
u They
include verbosity; tangentiality; cognitive
rigidity; lack of self-monitoring in verbal responses;
difficulty with pragmatic inference, with the
production and comprehension of humor, irony
sarcasm, metaphor, & ‘mind-reading’ (inference of
mental states); and with the production and
comprehension of emotional dimensions of language.
What are right/left differences due to?
- The LH has:
i.) Greater cell density
ii.) More nonmyelinated (= short) fibers, especially in the frontal regions =
good for computations requiring faster, routinized, localized processing
involving collections of cells working together in close spatial proximity.
- In the RH, more myelinated (long) axons may be specialized for computations that
do not require the same degree of localized, sequential processing or that require
integration of different types of input coming in from different parts of the brain.
- in sum: RHD patients exhibit difficulty processing
decoupled or alternative interpretations or meanings
of a stimulus
- A large body of work provides solid support for differences in how
the two hemispheres process meaning.
- The right hemisphere use slow, coarse-grained means:
- it shows longer lasting facilitation effects (maintains activation
over longer prime-target intervals) than the LH
- it is more likely than the LH to process weak or diffuse
associations and low frequency alternative meanings