Right hemisphere sensitivity to word

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Right hemisphere sensitivity to word sentence
level context Evidence From Event-Related Brain
Potentials.

• Coulson, S. Federmeier, K.D., Van Petten, C., and
  Kutas, M. (2005)
• JEP Learning, Memory, and Cognition.

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Gist

• Question Is right hemisphere message blind?
• Measurement ERP
• Paradigm associate priming without/within
  sentence context
• Answer RH is not message blind, but there is
  indeed hemispheric asymmetries in the use of word
  and sentence contexts

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Message-blind RH --the hypothesis

• LH
• has the ability to integrate syntactic,
  semantic, and pragmatic information to construct
  a message-level representation of meaning.

• RH
• its language competence extends only to
  word-level priming mechanisms

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Message-blind RH --why people made this claim?

• LH
• priming in RT to words embedded in normal or
  scrambled sentences (Faust et al. 1995)
• Larger priming effect when the amount of context
  is increased (Faust et al. 1993)
• Longer RT to words in implausible sentence
  context than plausible context (Faust, 1998)

• RH
• Contexts do not seem to facilitate or hinder the
  language process
• ?soRH seems to be blind to these message level
  information..

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Message-blind RH --however..

• LH

• RH
• Should be sensitive to some message level
  information, since when RH is damaged
• patients cannot understand certain kinds of
  jokes, metaphoric language, and sarcastic
  utterances
• Some studies did find sentence congruity effect
  in the RH (Chiarello, Liu, Faust, 2001 Faust,
  Bar-lev, Chiarello, 2003)

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• Ex1 word level context effect
• Lexical association
• Ex2 sentence level context effect
• Lexical association
• Sentence congruity

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Experimental design (EX1)
Primes are centrally presented, and targets are
lateralized to either visual field (split visual
field display).
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SPLIT VISUAL FIELD DISPLAY
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SPLIT VISUAL FIELD DISPLAY
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PROCEDURE
10001200ms

200ms
spare
0ms
200ms
tire
300ms
2500ms
?
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Prediction

• Ex1word level context effect
• Since both hemispheres are sensitive to word
  level info, similar-sized N400 context effects
  are expected

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Experiment 1results
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EX1 LVF/rh
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EX1 LVF/rh
N400
LPC
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EX1 RVF/lh
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Experimental design (EX2)
The cloze probability were matched between the
two types of congruous sentences (associated
unassociated) and also between the two types of
incongruous sentences. This was done to ensure
that the message level constraints are similar in
the associated and unassociated conditions.
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Prediction

• Ex1word level context effect
• Since both hemispheres are sensitive to word
  level info, similar-sized N400 context effects
  are expected
• Ex2sentence level context effect
• LH
• A large N400 congruity effect
• Negligible effects of association
• RH (if the message blind RH model holds)
• A large N400 association effect
• Negligible effects of context congruity

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Experiment 2results
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EX2 LVF/rh
N400
LPC
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EX2 RVF/lh
N400
LPC
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Summary

• word level association effects for both LVF/rh
  and RVF/lh presentation
• sentence level robust congruity effects for both
  LVF/rh and RVF/lh presentation
• ?the message-blind RH model is not supported
• At the sentence level, the congruity effect lead
  to a dramatic attenuation of the association
  effect.
• Lexical context is less important in sentence
  contexts

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unassociated
Association effect
associated
Association effect
unassociated
associated
5 µV
Congruity effect
incongruous
congruous
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Summary

• Although both hemispheres make use of word level
  as well as sentence level contexts, they seem to
  use them in different ways.
• LH seems to make use of lexical association only
  when the sentence context is incongruous.
• RH shows a smaller lexical association effect at
  the word level, which suggests that RH might be
  weaker to use this source of semantic context.
• RH shows the association effect in congruous
  sentences? there might be a greater reliance on
  word level relationships in the lexical
  integration processes in understanding sentences

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Questions

• Is the LPC the same thing as the P600?
• Do blinks also produce surges that might
  overshadow brain activity on the EEG?
• How common is subject attrition due to excessive
  artifacts?
• Onset or peak? Which point is more interesting?
  In what situations would one or the other be the
  focus?
• What if they ran their experiments on brain
  damaged patients ?
• Why was a naming paradigm chosen for the target
  as opposed lexical decision?
• Great Britain norms vs. US participants .isnt
  it problematic?
• Is the hemispheric asymmetry in reliance on
  lexical relationships has to do with other
  abilities commonly associated with RH function
  (e.g., spatial abilities).

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Other questions?
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ELECTRODE POSITIONS