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Pannekamp et al. (2005)

Prosody-driven Sentence Processing: An Event-related Brain Potential Study Ann Pannekamp, Ulrike Toepel, Kai Alter, Anja Hahne and Angela D. Friederici Presented by Laura Matzen, 9/1/2005. Pannekamp et al. (2005). Goal of study: Determine what causes the closure positive shift (CPS)

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Pannekamp et al. (2005)

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  1. Prosody-driven Sentence Processing: An Event-related Brain Potential StudyAnn Pannekamp, Ulrike Toepel, Kai Alter, Anja Hahne and Angela D. FriedericiPresented by Laura Matzen, 9/1/2005

  2. Pannekamp et al. (2005) • Goal of study: • Determine what causes the closure positive shift (CPS) • Is this effect driven by prosody alone or by other factors?

  3. Pannekamp et al. (2005) • Basic Design: • Systematically reduce linguistic content of sentences • Record ERPs in each condition to see if CPS is present in all cases or to see how it changes

  4. Background onEvent-related Potentials (ERPs)

  5. Background onEvent-related Potentials (ERPs)

  6. Background • Closure Positive Shift (CPS) • seen in response to normal spoken sentences • somehow related to intonation contour • Intonation contour • “sentence melody” • provides information about syntactic structure, sentence mode • fundamental frequency – F0

  7. Frequency “Actually, we were the ones who said we didn’t want a regular cake, so you can blame it on us.”

  8. Frequency “Actually, we were the ones who said we didn’t want a regular cake, so you can blame it on us.”

  9. Intonational Phrases (IPh) • One or more in each sentence • Group and organize words into phrases • Structure is usually determined by syntax

  10. Intonational Phrases (IPh) • “...defined as containing at least one nuclear accent and a boundary tone at their right edges” • Pitch contour drops at the end, resets at start of the next IPh • Last syllable usually lengthened • Often followed by a pause

  11. Examples • She went to the store, then she picked up the dry cleaning on the way home. • She went to the store, then she dropped the kids off at school, then she went home.

  12. Intonational Phrases (IPh) • Seem to be secondary to syntax in some ways • supporting role • BUT, listeners can identify prosodic boundaries in the absence of semantic and syntactic information (de Rooij, 1975)

  13. Intonational Phrases (IPh) • Beckman (1996) “the prosodic structure of the utterance has to be seen as a full grammatical property also requiring its own parsing” • However, it might be harder to process prosody in absence of other linguistic information • Off-line behavioral studies can’t address this issue

  14. Steinhauer et al. (1999) • Studied prosody with ERPs • Two sentence types: 1 or 2 IPh boundaries • Saw positive-going waveform in response to all boundaries – CPS • Possible Confound: • Close relationship between prosody and syntax • CPS could still be related to processing syntactic boundaries, not just prosodic boundaries

  15. Steinhauer & Friederici (2001) • ERP study with delexicalized speech • Filtered to removed phonemic, semantic and syntactic information • Only prosodic info left (pitch, amplitude, rhythm)  CPS in this case could only be caused by prosody

  16. Steinhauer & Friederici (2001) • Results • Strange-looking CPS at first boundary • No CPS at second boundary • Contingent negative variation (CNV) across whole sentence • Is this because the sentences are so unnatural? Is this task completely different from language processing?

  17. Meyer et al. (2002) • fMRI study • Very different responses to natural speech and delexicalized speech • Response to prosody stronger in right hemisphere • “strong evidence that pitch processing in the absence of additional linguistic information such as syntax and/or semantics takes place in right hemisphere regions”

  18. Current Experiments • Motivations: • Investigate partial replication of CPS findings by Steinhauer & Friederici (2001) • Why didn’t they get the expected results? • Try using more natural stimuli • See if CPS shifts to the right hemisphere as segmental information is removed

  19. Experiments • Experiment 1: Normal sentences • Normal semantic, syntactic and phonemic info • Experiment 2: Jabberwocky sentences • Remove semantic information • Experiment 3: Pseudo sentences • Remove semantic and syntactic information • Experiment 4: Hummed sentences • Remove semantic, syntactic, and phonemic info (only prosody left)

  20. Expt 1: Normal Sentences A1: [Kevin promises mom to sleep]IPh1 [and to be a good boy for a while.] B1: [Kevin promises]IPh1 [mom to kiss]IPh2 [and to be a good boy for a while.]

  21. Expt 1: Normal Sentences A1: one IPh boundary at 1950 msec B1: two IPh boundaries at 950 and 2700 msec • “First part” (subject + verb) of sentence longer than A1 • High boundary tone at end of first part • Longer pause after first part • Both conditions have IPh boundary after second verb (marked by high boundary tone)

  22. Expt 2: Jabberwocky Sentences All content words replaced with pseudo words A2: [The bater rabels Onna to lubol]IPh1 [and the rado to nupe.] B2: [The bater rabels ]IPh1 [Onna to lubol]IPh2 [and the rado to nupe.]

  23. Expt 2: Jabberwocky Sentences A2: one IPh boundary at 2100 msec B2: two IPh boundaries at 1100 and 2600 msec • “First part” (subject + verb) of sentence longer than A2 • High boundary tone at end of first part • Longer pause after first part • Both conditions have IPh boundary after second verb (marked by high boundary tone)

  24. Expt 3: Pseudo Sentences All function and content words replaced with pseudo words A3: [Bater saklimm Onna ko labei keg ]IPh1 [nug som Rado lie nupes.] B3: [Bater saklimm]IPh1 [Onna ko labei keg]IPh2 [nug som Rado lie nupes.]

  25. Expt 3: Pseudo Sentences A3: one IPh boundary at 2000 msec B3: two IPh boundaries at 920 and 2400 msec • “First part” (subject + verb) of sentence longer than A3 • High boundary tone at end of first part • Longer pause after first part • Both conditions have IPh boundary after second verb (marked by high boundary tone)

  26. Expt 4: Hummed Sentences A4: [mm mmm mmmm mm mmmm]IPh1 [mmmm mmm mmm mmm mmmmm.] B4: [mm mmm]IPh1 [mmmm mm mmm]IPh2 [mmmm mmm mmm mmm mmmmm.]

  27. Expt 4: Hummed Sentences A4: one IPh boundary at 1850 msec B4: two IPh boundaries at 850 and 2150 msec • Longer pause after first part • High boundary tone at end of first part • (First part itself is NOT longer in this case) • Both conditions have IPh boundary after second verb (marked by high boundary tone)

  28. Procedure • Subjects only saw one type of sentence • Auditory presentation for all sentences • Trial followed by a probe word • Subjects had to say whether word was in sentence or not • (Words were placed randomly into hummed filler sentences)

  29. Data Collection • 23 Ag/AgCl electrodes • 200 msec prestimulus baseline • Averages computed over whole sentences – 4500 msec segments

  30. Results

  31. A1: IPh at 1950 ms Response at 2000 ms ------------------------------ B1: IPh1 at 950 ms Response at 1500 ms IPh2 at 2700 ms Response at 2700 ms

  32. A2: IPh at 2100 ms Response at 2200 ms ------------------------------ B2: IPh1 at 1100 ms Response at 1500 ms IPh2 at 2600 ms Response at 2800 ms

  33. A3: IPh at 2000 ms Response at ms ------------------------------ B3: IPh1 at 920 ms Response at 1500 ms IPh2 at 2400 ms Response at 2500 ms

  34. A4: IPh at 1850 ms Response at 2200 ms ------------------------------ B4: IPh1 at 850 ms Response at 1000 ms IPh2 at 2150 ms Response at 2000-2500 ms Negative peak from 500-1000 ms

  35. Waveforms measured from offset of 1st sentence fragment

  36. Their interpretation... • Positivity resembles CPS • Observed in all experimental conditions • Related to processing of prosodic boundaries • Scalp distribution changes across conditions

  37. Their interpretation... • CPS associated with first IPh seems related to the amount of segmental content in sentences • Moved forward and rightward as info decreased • CPS associated with second IPh seems UNrelated to amount of segmental content

  38. Scalp Distributions – IPh1 • Experiment 1: CPS over whole head • Experiment 2: CPS at midline and lateral sites, also moves to anterior sites • Experiment 3: Moves to right anterior sites • Experiment 4: CPS broadly distributed

  39. Scalp Distributions • First IPh: • CPS moved anterior sites as linguistic information decreased • CPS for psuedo sentences moved rightward, but not for hummed sentences (possible explanation – left hemisphere processing timing of hums?)

  40. Scalp Distributions • Second IPh: • CPS distributed broadly over midline sites • also over lateral sites for normal and pseudo sentence (why not for other types of sentences?) • CPS moved rightward for hummed sentences ONLY (CPS not seen here at all in previous study- conclude that naturalness is important)

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