Online Syntactic Prediction in Agrammatic Aphasia: Evidence from ERPs
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1
Northwestern University, Department of Communication Sciences and Disorders, United States
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2
Northwestern University, Department of Linguistics, United States
Background. Agrammatic aphasia is characterized by selective comprehension impairments in complex sentences with long-distance dependencies. Emerging data suggest that rather than impaired grammatical knowledge or working memory, comprehension breakdown may result from impaired linguistic prediction [1,2]. While prediction is used on all levels of linguistic representations in normal sentence processing, studies with aphasic individuals have focused primarily on lexical- and thematic-prediction, with little attention to syntactic prediction, which is critical to complex sentence comprehension.
This study examined syntactic prediction using cataphoric dependencies, which involve a long-distance relation between a pronoun and its antecedent, as in (1a/b). A cataphoric pronoun triggers prediction for an upcoming antecedent NP in a grammatically licit position using lexical features like animacy [3,4]. Thus, once the reader encounters the pronoun ‘he’, he/she predicts an animate singular noun like ‘the driver’ to appear in a later position in the sentence. Therefore, cataphora resolution allows us to investigate the role of syntactic prediction in online dependency formation.
Methods. Six individuals with agrammatic aphasia and 15 healthy control participants read 200 sentences as in (1a-d) presented word-by-word (500ms/word) while EEG was continuously recorded from 32 electrodes. We manipulated the dependency (CATAPHORA vs. NO-DEPENDENCY) and animacy (MATCH vs. MISMATCH) of the antecedent following [4].
(1) a/b. After he checked the map, the driver/truck driver suddenly…
c/d. He checked the map, after the driver/truck driver suddenly…
In (1a/b), the pronoun is syntactically linked to the antecedent (the driver/truck driver). Because the pronoun ‘he’ is animate, prompting the parser to actively look for an animate antecedent to form a dependency, we expected an N400 response in (1b, truck-inaimate) relatively to (1a, driver-animate) as an index of failed prediction. Because direct comparison of truck-driver can also independently elicit an N400 due to lexical differences, we added a control comparison in (1c) vs. (1d) where the pronoun-antecedent dependency is grammatically impossible. A larger N400 in (1b-1a) vs. (1d-1c) was predicted to reflect syntactic prediction required in the former, but not in the latter.
Results. Both groups showed main effects of DEPENDENCY and ANIMACY, where a larger N400 component was elicited by inanimate vs. animate nouns in both dependency conditions. However, the interaction DEPENDENCYxANIMACY was only significant in the control group, reflecting a larger N400 in (1a) vs. (1b) than (1c) vs. (1d), indicating failed syntactic prediction. The agrammatic group showed similar N400 amplitudes in both contrasts, suggesting that syntactic prediction was not employed during long-dependency formation in agrammatic aphasia.
Conclusion. These findings indicate that individuals with agrammatic aphasia exhibit patterns of online processing consistent with impaired syntactic prediction. This suggests that in online cataphoric dependency resolution, individuals with agrammatic aphasia attempt to form syntactic dependencies only after the antecedent is confirmed, using a bottom up, rather than top down processing strategy. This pattern is in line with the evidence suggesting delayed cataphoric dependency formation in agrammatic aphasia [5].
References
[1] Mack et al. (2013). Journal of Neurolinguistics, 26(6), 619-636.
[2] Meyer et al. (2012). Journal of Neurolinguistics, 25, 31-43.
[3] Kazanina et al. (2007). Journal of Memory and Language, 56(3), 384-409.
[4] Kazanina, N., & Stothart, G (2012). Paper presented at 2012 CUNY conference.
[5] Hsu et al. (2014). Paper presented at the 2014 Academy of Aphasia.
Keywords:
agrammatic aphasia,
agrammatic sentence comprehension,
online syntactic prediction,
long-distance dependency resolution,
ERPs (Event-Related Potentials)
Conference:
54th Annual Academy of Aphasia Meeting, Llandudno, United Kingdom, 16 Oct - 18 Oct, 2016.
Presentation Type:
Platform Sessions
Topic:
Student Submissions
Citation:
Hsu
C,
Yoshida
M,
Barbieri
E and
Thompson
CK
(2016). Online Syntactic Prediction in Agrammatic Aphasia: Evidence from ERPs.
Front. Psychol.
Conference Abstract:
54th Annual Academy of Aphasia Meeting.
doi: 10.3389/conf.fpsyg.2016.68.00119
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Received:
30 Apr 2016;
Published Online:
15 Aug 2016.
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Correspondence:
Ms. Chien-Ju Hsu, Northwestern University, Department of Communication Sciences and Disorders, Evanston, IL, 60208, United States, chienjuhsu@u.northwestern.edu