233 Brain

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Basic neuroscience Language Decision Making
J. Lauwereyns, Ph.D. Professor Graduate School of
Systems Life Sciences Kyushu University jan_at_sls.k
yushu-u.ac.jp
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Language Unique to humans?
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Evolution and Physiology of Language

• Human language is different because it is more
  productive
• can produce new signals to represent new ideas
• Chimpanzees can learn to communicate using sign
  language or symbols, but different from human
  language
• symbols used to request but rarely to describe
• seldom recombine in new combinations
• say more than they understand, the opposite of
  children

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Language as a Special Module

• Humans have evolved with something that enables
  them to learn language easily
• Chomsky and Pinker a language acquisition device
• children learn language with ease, including
  children of deaf parents
• deaf children learn sign or invent one of their
  own
• not likely a separate module since most language
  areas used for other functions, e.g., memory,
  music perception
• intelligence may be by-product of language

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Broca vs Wernicke
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Brocas Aphasia

• Also called non-fluent aphasia
• severe deficits in language production caused by
  damage to Brocas area, and other cortical and
  subcortical structures
• difficulty pronouncing, gesturing and writing as
  well as understanding complex speech
• uses and understands nouns and verbs more easily
  than closed-class words, e.g., prepositions,
  pronouns
• ignores grammar and relies on inferences
• but, can usually recognize when something is
  wrong with sentence even if they cannot correct
  it

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Wernickes Aphasia

• Also called fluent aphasia
• caused by damage to left temporal cortex
• seriously impaired language comprehension
• difficulty finding the right word and trouble
  recalling names of objects
• grammatical but often nonsensical speech
• perhaps because cant find words due to rapid
  speech
• but, can pronounce clearly, fluently and rapidly

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Wernicke Comprehension, Meaning
Broca Production, Syntax
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What about language on the left?
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What about language on the left?

• Lateralization of Brain Function
• Two hemispheres are not mirror images of each
  other
• left hemisphere controls right side of body
• right controls left side
• taste and smell input to same side
• Lateralization is the specialization of labor
  between the two hemispheres
• left hemisphere specialized for language
• right specialized for complex visual-spatial
  tasks and synthetic processing

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• Handedness and Language Dominance
• Right handedness a heritage
• 10 of people are left-handed or ambidextrous
• 90 of prehistoric drawings show tools in right
  hand
• most chimps and other primates are right handed
• Left handers
• have equal as well as left or right hemisphere
  dominance for speech
• if right is dominant, left hemisphere contributes
  more to spatial perception
• Corpus Callosum is thicker for greater
  communication

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Not quite as famous as Sir Edmund Hillary,
but
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Where does Corballis get his idea?

• Corticol control of manual movements
• Primates acquiring sign language
• The mirror system in monkeys
• Left hemisphere for speech and hands
• Deaf use sign languages with full syntax
• Nonverbal gestures during speech
• FOXP2 gene mutated about 200,000 years ago

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FOXp2
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Where does Corballis get his idea?

• Corticol control of manual movements
• Primates acquiring sign language
• The mirror system in monkeys
• Left hemisphere for speech and hands
• Deaf use sign languages with full syntax
• Nonverbal gestures during speech
• FOXP2 gene mutated about 200,000 years ago

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The mirror system
Ventral premotor area monkey homologue of
Area 44 in frontal cortex, that is, Brocas
Area Studied by Rizzolatti and co.
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The mirror system

• Neurons in ventral premotor area
• activated both when the subject performs an
  action and when the subject observes someone else
  perform the same action
• Abstract action representation
• This system likely plays a role both in
  recognising and planning actions (thinking about
  actions)

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Importance of the mirror system?

• Understanding action?
• Origins of language?
• Empathy?
• Morality?
• (some other day)

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On reasoning and decision making
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On reasoning and decision making

• More complex with language
• Consider context
• Imagine different scenarios

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Most basic structure for decision making
Response
Stimulus
Stimulus Response Matrix
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Signal detection theory
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Bias
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Consider different decision contexts
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Consider different decision contexts
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Consider different decision contexts
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Bias
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Sensitivity
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Sensitivity
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Ways to improve sensitivity
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Ways to improve sensitivity
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Ways to improve sensitivity
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How does it really work?
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General increase
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General increaseProspective, additive

• Bias in anticipatory activity
• Linearly enhances sensory activity
• Response Input Reward Bias
• Prefrontal cortex, basal ganglia
• Superior colliculus

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Improved discrimination
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Improved discriminationSynergistic,
multiplicative

• Sensory properties
• Non-linearly enhanced by reward
• Response Input Reward Gain
• Prefrontal cortex, parietal cortex
• Superior colliculus

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Dopamine
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Dopamine
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Excitation
Dopamine
Synergistic, multiplicative
Disinhibition
Sensitivity
Prospective, additive
Bias
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How do we process conflicts?

• Paradox
• Immediate reward
• versus Delayed gratification

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The classic Stroop

• James Ridley Stroop, inventive priest
• Present participants with a word printed in a
  certain colour
• GREEN
• Name the colour
• Interference from irrelevant word
• RT Incompatible gt Neutral gt Compatible
• Evidence of conflict

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fMRI studyMcDonald et al

• Using a cued Stroop task
• Trial begins with
• word read the word
• colour name the colour
• Task instruction changes trial by trial
• Separate effects
• Instruction-related activity
• Response-related activity

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Response- related activity
Congruent stimulus
Incongruent stimulus
RED
GREEN
COLOUR NAMING
Instruction- related activity
red
red
RED
GREEN
WORD READING
red
green
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Interpretation

• In DLPFC
• Stronger activity in colour trials than in
  word trials
• Effects of task instruction, but not congruency
• Especially before target onset (during
  preparation)
• In ACC
• Stronger activity in incongruent trials as
  compared to congruent trials
• Effects of congruency, but not task instruction
• Especially after target onset, or even after
  response

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Conclusions

• Dorsolateral prefrontal cortex
• Seems important for representing the task
  instruction
• Ordering what to do
• Anterior cingulate cortex
• Seems involved in situations of conflict
• Performance monitoring
• Evaluating what you do