Text of Language in context: Emergent features of word, sentence, and narrative comprehension Xu, J.,...
Language in context: Emergent features of word, sentence, and
narrative comprehensionXu, J., Kemeny, S., Park, G., Frattali,
C., & Braun, A.2005 - NeuroImage
Research Gap to be Filled…
Context (broadly construed) has widespread effects on neural activity; context in language processing are a natural area of interest
Most previous research has focused only on one level of text processing (e.g., word, sentence, discourse-level)
Work focusing on discourse-level has not examined the role of context within the establishment of a discourse representation
Background on discourse-level
“mental models” or “situation models” - mental representation of a described state of affairs.
Situation model NOT equal to a schema– Schemas represent stereotypical situation (e.g.,
visiting a restaurant)– Situation model is mental representation of
specific situation (e.g., a specific visit to a restaurant on a certain day in your memory)
Situation model draws upon prior knowledge, constrained by attentional & memory capacities, and utilization of abstraction, imagery, and inference
In the present study…
fMRI methodologyText presented at word, sentence, and
discourse levels– Drawn from Aesop’s fables*
No metalinguistic tasks used (to reduce potential for brain activity from cognitive strategy)
Hypothesized brain regions
Across all text levels, LH Perisylvian areas should be active:
Sentence-level: more widespread perisylvian, esp. frontal operculum (covering the insula, aka Island of Reil)
Discourse-level: extra-sylvian activation
RH activity increase w/ increasing context
Both LH & RH activity early in discourse-level processing, RH activity stronger at end, when situation model construction becomes coherent and well-developed
22 right-handed male english speakers (21-65 years old) with no history of neurological impairment or psychiatric disease*
BOLD contrast fMRIs using a whole-body 3T GE scanner
Methods cont… Aesop’s fables were used (with some edits to make
the English more modern) The Birds, the Beasts, and the Bat
THE BIRDS waged war with the Beasts, and each were by turns the conquerors. A Bat, fearing the uncertain issues of the fight, always fought on the side which he felt was the strongest. When peace was proclaimed, his deceitful conduct was apparent to both combatants. Therefore being condemned by each for his treachery, he was driven forth from the light of day, and henceforth concealed himself in dark hiding-places, flying always alone and at night.
(He winds up friendless who plays both sides against the middle)
Words in each fable were coded for (1) part of speech, (2) frequency, (3) imageability, (4) concreteness, (5) grammatical category*
Words in each sentence coded for 15 syntactic attributes
Sentences coded for (1) # of words, (2) propositions, (3) verbs, (4) thematic roles
9 fables selected that were matched on ALL aforementioned features*
Words from 9 fables were presented in three conditions: – Random word– Individual, unconnected sentences– Coherent narrative (full fable)
Comparison baseline controls were random consonant letter strings*
Comparisons… Word/Sentence/Narrative minus Random letter
string Across levels:
– Sentence-Word, Narrative-Word, Narrative-Sentence Within narrative: grammar codes
– Implicated in linking text w/ prior knowledge, accessing of episodic memory
hippocampus, temporal sulcus, amygdala, etc.
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Results: Contrasts Across Levels
Left frontal operculum,Left TPO cortex
MTG, TPO cortex
Medial prefrontal cortices, precuneus, etc. (extrasylvian areas)
Summary of Across-Level ContrastsIncreasing parasylvian activity with
increasing language complexityIncreasing bilateral activation with
increasing language complexitySelective perisylvian & extrasylvian
activity only with narrative-level
Results: Within-Narrative Strong shift in lateralization (L to R) Establishment of setting & plot associated
with mostly LH Resolution of narrative associated with RH
LH activation early in narrative likely reflects construction of textbase-level features
Bilateral activation late in narrative likely reflects RH contribution to “global synthesis” of story as a whole (e.g., extraction of a moral from the story)
Word-level: some activity in supplementary motor cortex areas (despite lack of motor response in task)– Perhaps subarticulation?– Perhaps stronger ties between language
& motor function than previously believedSentence-level: left putamen/ventral
thalamus activity (part of motor circuit)– Perhaps motor circuit plays role in serially
organizing syntactic structure?
Questions… If narrative processing leads to combinations of
perisylvian & extrasylvian brain areas, would more frequent readers (e.g., those more familiar with certain genres which promote situation models) show different brain activation patterns?
might familiarity (previous knowledge) of Aesop’s fables have contributed in part to the processing load of narratives over time?
what might happen if we asked the participants to create a story in the word and sentence conditions (in which they might think of Aesop’s fables right away as well.)
Any reason for using consonant strings as a baseline condition instead of letting the participants rest?
Why use random consonants as a base? Why not pseudowords with vowels? Does it matter?
Although 350ms is still slower than normal reading speed, it seems to be much faster than most imaging studies run on fMRI. (is it true?) Do they need to compromise anything because of the fast display of stimuli? (e.g. noisier data or more assumption in the data analyses?)
First of all, what are sham blocks and sham contrasts. What do they have to do with vectors?
And is it really possible for 9 different fables to be matched on so many variables?
Why white font on a black background? Does it matter?
For ERPs, I understand that we want to stay with younger participants (20s range). Why the variety in ages?? 21 to 65 yrs old? Can they do that?
Questions Perhaps if subjects were shown a series of pictures
that told a story, simulating the narrative condition but without language, it would become clear if the additional activity was caused by linguistic context or something else (like working memory load)?
don't sentence level computations take some of extra-linguistic operatoin as well since people can use semantics in the sentence level too?
I'm just wondering how much does this has to do with the different speed of activation pattern across hemispheres. (LH is faster, and RH is slower). Is it possible that since the RH is slower, the activation get 'accumulated over time and appears to be more prominent at the story's conclusion?