Transcript Chapter 9 Language and the Brain Second Edition Cognitive

Lecture 3
12 Oct., 2005
Language and the Brain
Helena Gao
Lecture 3; Oct. 12, 2005
Required readings:
 Gazzaniga, M., Ivry, R., & Mangun, G. (2001). Cognitive
Neuroscience: The Biology of the Mind. New York:
W.W. Norton and Co. Chapter 9: Language and the
brain, pp. 351-399.
 Vygotsky, L. (1996). Thought and Language. Newly
revised and edited by Alex Kozulin. The MIT Press.
Chapter 4: The Genetic Roots of Thought and Speech.
pp. 68-95.
Recommended readings:
 Shapiro, K., & Caramazza, A. (2003). The
representation of grammatical categories in the brain.
Trends in Cognitive Science, 7(5), 201-206.
Brain areas involved in Language
Three major types of Aphasia
Rosenzweig: Table 19.1, p. 615
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Borca’s aphasia
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Wernicke’s aphasia
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Nonfluent speech
Fluent speech but unintelligible
Global aphasia
Total loss of language
Others: Conduction, Subcortical, Transcortical
Motor/Sensory (see also Kandel, Table 59-1)
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Broca’s Aphasia
Brodmann 44, 45
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Lesions in the left inferior frontal region (Broca’s area)
Nonfluent, labored, and hesitant speech
Most also lost the ability to name persons or subjects
(anomia)
Can utter automatic speech (“hello”)
Comprehension relatively intact
Most also have partial paralysis of one side of the body
(hemiplegia)
If extensive, not much recovery over time
Wernicke’s Aphasia
Brodmann 22, 30
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Lesions in posterior of the left superior temporal gyrus,
extending to adjacent parietal cortex
Fluent speech
But contains many paraphasias
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“girl”-“curl”, “bread”-“cake”
Syntactical but empty sentences
Cannot repeat words or sentences
Unable to understand what they read or hear
Usually no partial paralysis
Sign Languages
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Full-fledged languages, created by hearing- impaired
people (not by Linguists):
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Dialects, jokes, poems, etc.
Do not resemble the spoken language of the same area
(ASL resembles Bantu and Navaho)
Pinker: Nicaraguan Sign Language
Another evidence of the origins of language (gestures)
Most gestures in ASL are with right-hand, or else
both hands (left hemisphere dominance)
Signers with brain damage to similar regions show
aphasia as well
Spoken and Sign Languages
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Neural mechanisms are similar
fMRI studies show similar activations for both
hearing and deaf
But in signers, homologous activation on the
right hemisphere is unanswered yet
Dyslexia
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Problem in learning to read
Common in boys and left-handed
High IQ, so related with language only
Postmortem observation revealed anomalies in the
arrangement of cortical cells
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Micropolygyria: excessive cortical folding
Ectopias: nests of extra cells in unusual location
Might have occurred in mid-gestation, during cell
migration period
Acquired Dyslexia = Alexia
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Disorder in adulthood as a result of disease or
injury
Deep dyslexia (pays attn. to wholes):
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Surface dyslexia (pays attn. to details):
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“cow” -> “horse”, cannot read abstract words
Fails to see small differences (do not read each letter)
Problems with nonsense words
Nonsense words are fine
Suggests 2 different systems:
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One focused on the meanings of whole words
The other on the sounds of words
Electrical Stimulation
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Penfield and Roberts (1959): During epilepsy surgery
under local anesthesia to locate cortical language areas,
stimulation of:
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Large anterior zone:
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Both anterior and posterior temporoparietal cortex:
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stops speech
misnaming, impaired imitation of words
Broca’s area:
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unable comprehend auditory and visual semantic material,
inability to follow oral commands, point to objects, and understand
written questions
PET by Posner and Raichle (1994)
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Passive hearing of words activates:
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Repeating words activates:
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No activation in Broca’s area
But if semantic association:
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Both motor cortices, the supplemental motor cortex,
portion of cerebellum, insular cortex
While reading and repeating:
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Temporal lobes
All language areas including Broca’s area
Native speaker of Italian and English:
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Slightly different regions
Due to phonetic alphabet of Italian… (“ghotia”)
PET by Damasio (1989)
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Different areas of left hemisphere (other than
Broca’s and Wernicke’s regions) are used to name (1)
tools, (2) animals, and (3) persons
Stroke studies support this claim
Three different regions in temporal lobe are used
ERP studies support that word meaning are on
temporal lobe (may originate from Wernicke’s area):
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“the man started the car engine and stepped on the
pancake”
Takes longer to process if grammar is involved
Williams Syndrome
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Caused by the deletion of a dozen genes from one
of the two chromosomes numbered 7
Shows dissociation between language and
intelligence, patients are:
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Fluent in language
But cannot tie their shoe laces, draw images, etc.
Developmental process is altered:
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Number skills good at infancy, poor at adulthood
Language skills poor at infancy, greatly improved in
adulthood
Guest speaker in the colloquium, Annette KarmiloffSmith, claims the otherwise:
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Development alters the end result of the syndrome (?)
Lateralization of the Brain
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Human body is asymmetrical: heart, liver, use of
limbs, etc.
Functions of the brain become lateralized
Each hemisphere specialized for particular ways
of working
Split-brain patients are good examples of
lateralization of language functions
Lateralization of functions
(approximate)
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Left-hemisphere:
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Sequential analysis
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Analytical
Problem solving
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Right-hemisphere:
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Simultaneous analysis
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Visual-Spatial skills
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Language
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Cognitive maps
Personal space
Facial recognition
Drawing
Emotional functions
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Synthetic
Recognizing emotions
Expressing emotions
Music
Other studies
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Right ear advantage in dicothic listening:
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Words in left-hemisphere, Music in right
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Due to interhemispheric crossing
Supported by damage and imaging studies
But perfect-pitch is still on the left
Asymmetry in planum temporale:
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Musicians with perfect-pitch has 2x larger PT
Evident in newborns, thus suggesting innate basis for
cerebral specialization for language and speech
The Storage of Words and Concepts:
The Mental Lexicon
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The Mental Lexicon:
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a mental store of information about word that includes semantic
information, syntactic information, and the details of word forms.
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Most psycholinguistic theories agree on the central role for a
mental lexicon in language
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Some theories propose one mental lexison for both language
comprehension and production
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Other models distinguish between input and output lexia
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The representation of orthographic and phonological forms must be
considered in any model.
The mental lexicon is thought to be organized as information-specific networks
– a model proposed by William Levelt in 1994
W. W. Norton
Support for the model
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Semantic Priming Studies
Using a lexical decision task
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Subjects are faster and more accurate at making the
lexicon decisions when the target is proceeded by a
related prime (e.g., car truck) than a unrelated prime
(e.g., whip truck).
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Expectancy-induced priming might occur if the time
bet. The presentation of primes and targets is long
(e.g., > 500 msec) and the proportion of related
word pairs are like car-truck, cat-dog, etc.
The Nature of Conceptual or
Semantic Representation
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Question:
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Is the same conceptual representation of a robin
activated regardless of whether one hears the word
robin or sees one flying?
A model proposed by Collins and Loftus (1975)
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Word meanings are represented in a semantic
network in which words, represented by conceptual
nodes, are connected with each other.
• Although this semantic network model (Collins & Loftus, 1975)has been extremely influential,
it is a matter of debate how Word meanings are represented.
• No matter how they are represented, it is agreed that a mental store of word meanings is crucial
to
normal language comprehension and production.
W. W. Norton
Support from neurological evidence for the
semantic network idea
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Different types of neurological problems create deficits
in understanding and producing the appropriate
meaning of a word or concept. Patients with Wernicke’s
aphasia makes errors in speech production that are
known as semantc-paraphasias (e.g., using the word
horse to mean cow)
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Patients with progressive-semantic dementia initially
show impairments in the conceptual system, while
other mental and language abilities are spared.
Evidence from research done by E. Warrington
(1970s-1980s)
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Findings: semantic problem can be localized
specifically to certain semantic categories , such
as animals versus objects.
E.g., patients who had great difficulties pointing
to pictures of food or living things when
presented with a word, whereas their
performance with man-made objects like tools
was much better.
Evidence from H. Damasio and her colleagues’
studies (1996)
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Investigated a large population of patients with brain lesions
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A naming task in three different conditions: (1) naming famous
faces, (2) naming animals, and (3) naming tools
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30 patients, 29 of whom had a lesion in the left hemisphere,
showed impairments in this task.
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7 patients demonstrated impairment in naming faces, 5 in
naming animals; and 7 in naming tools. The remaining 11had a
combination of problems in word retrieval for faces, animals,
and tools, faces and animals, or animals and tools, but never for
the combination of faces and tools together without also a
deficit in animals.
Location of the brain lesions that are correlated with selective deficits in naming persons, animals,
or, tools. (Damasio et al (1996)
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Pet Scanning
• Brain damage in the left
temporal pole (TP)
correlated with problems in
retrieving the names of persons
• Lesions in the anterior part of the
Left inferior temporal (IT) lobe
correlated with problems in
naming animals
• Damage to the posterolaterol
part of the left inferior temporal
lobe, along with lateral
temporo-occipito-parietal
junction (IT+),
was correlated with problems
in retrieving the names of tools
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W. W. Norton
Three levels of Representation for Word Knowledge – predicated by cognitive models of word
Production Based on Damasio et al’s Results (Caramazza, 1996)
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Schematic representation of the
components that are involved in
spoken and written language
comprehension.
Input can enter via either auditory
(spoken word) or visual (written word)
modalities.
The flow of info is bottom up, from
Perceptual identification to
“higher-level” word and lemma
activation.
Interactive models of language
Understanding would predict top-down
influence to play a role as well.
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Spoken Input – lack of segmentation
Courtesy of Tamara Swaab. © 1997 by the Massachusetts Institute of Technology.
Courtesy of Tamara Swaab. © 1997 by the Massachusetts Institute of Technology.
Spectral properties vary according to sounds (Klatt, 1989)
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A model for letter recognition, the pandemonium model (Selfridge, 1959)
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McClelland, J.L., and Rumelhart, D.E. (1986). Parallel Distributed Processing: Explorations in the
Microstructure of Cognition. Vol. 2: Psychological and Biological Models. Cambridge, MA: MIT Press.
Fragment of a connectionist network for letter recognition (McCleland & Rumelhart, 1981)
A cohort model of British psychologist
William Marslen –Wilson
(Marslen –Wilson
& Tyler, 1980)
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ERPs recorded in response to sentences that start with before (dashed lines) and after (solid lines)
Munte et al (1998).
Task: “After/Before the scientist submitted the paper, the journal changed its policy”
Before are
More
Negative in
polarity
Summary of lesions in the anterior superior temporal cortext that lead to deficits in
Syntactic processing (Mazoyer et al, 1993)
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Outline of the theory of
speech production developed by
William Levelt (1999)
Adapted from Levelt, W.J.M., The Architecture of Normal Spoken Language Use, in Blanken, G., Dittman,
J., Grimm, H., Marshall, J.C., and Wallesh, C-W. (Eds.), Linguistic Disorders and Pathologies: An
International Handbook. Berlin: Walter de Gruyter, 1993
Speech Production
Method:
Stimuli: words in Dutch ->
Equ.: ERP
Proc.:
Subjects were asked to
make a response only
when the words representing
the pic. Started with a “b’,
and to withdraw their
response when the word
Started with a “s”.
Adapted from van Turennout, M. Hagoort, P., and Brown, C.M. (1999). Brain activity during speaking: From
syntax to phonology in 40 milliseconds. Science, 280, 572-574.
A study to test whether
Lemma selection indeed
Precedes activation of
Appropriate lexeme (as
In Levelt’s model) by
Van turennout (1999)