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.

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

Message-blind RH --the hypothesis

LHhas 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

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

so…RH seems to be blind to these message level information..

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)

Ex1 [word level context effect]Lexical association

Ex2 [sentence level context effect]Lexical associationSentence congruity

Experimental design (EX1)

Associated UnassociatedCongruous

They were truly stuck, since she didn’t have a spare TIRE.

… Ellen leaned over and borrowed my spare PENCIL.

Incongruous

… Ellen leaned over and borrowed my spare TIRE.

They were truly stuck, since she didn’t have a spare PENCIL.

Primes are centrally presented, and

targets are lateralized to either visual field (split visual field display).

SPLIT VISUAL FIELD DISPLAY

SPLIT VISUAL FIELD DISPLAY

PROCEDURE

++++

200ms

200ms

1000~1200ms

300ms

2500ms

spare

tire

?

0ms

Prediction

Ex1[word level context effect]Since both hemispheres are sensitive

to word level info, similar-sized N400 context effects are expected

Experiment 1—results

EX1

LVF/rh

EX1

LVF/rh

N400LPC

EX1

RVF/lh

Experimental design (EX2)

Associated UnassociatedCongruous

They were truly stuck, since she didn’t have a spare TIRE.

… Ellen leaned over and borrowed my spare PENCIL.

Incongruous

… Ellen leaned over and borrowed my spare TIRE.

They were truly stuck, since she didn’t have a spare PENCIL.

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.

Prediction

Ex1[word level context effect] Since both hemispheres are sensitive to word

level info, similar-sized N400 context effects are expected

Ex2[sentence 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

Experiment 2—results

N400LPC

EX2

LVF/rh

N400LPC

EX2

RVF/lh

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

5 µV

Association effect

Association effect

Congruity effect

unassociated

associated

unassociated

associated

incongruous

congruous

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

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 ….isn’t 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).

Other questions?

ELECTRODE POSITIONS