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Sahin, Pinker, Cash, Schomer, & Halgren (2009)

Sahin, Pinker, Cash, Schomer, & Halgren (2009). Sequential processing of lexical, grammatical, and phonological information within Broca’s area. Broca’s Area. Implicated in several kinds of processes Language Phonology Morphology Syntax More generally Sequential ordering?

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Sahin, Pinker, Cash, Schomer, & Halgren (2009)

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  1. Sahin, Pinker, Cash, Schomer, & Halgren (2009) Sequential processing of lexical, grammatical, and phonological information within Broca’s area

  2. Broca’s Area • Implicated in several kinds of processes • Language • Phonology • Morphology • Syntax • More generally • Sequential ordering? • (Near motor face and hand regions)

  3. Broca’s Area = 44 & 45 Brodmann Areas Defined histologically

  4. Depth Electrodes • Used in surgical patients only • - Seizures not sufficiently controlled by meds • Surgery to excise tissue causing seizures • Main purpose to help localize seizure focus • Contacts every 5mm at different • depths along a single needle • - Electrode diameter = 1 mm • Record from adjacent pairs (= bipolar) • - Less noisy • - Polarity reversals when cross sources • - Allows better localization of seizure source • Record Local Field Potentials (LFP)

  5. Participants (Patients) • Inclusion criteria: • - No clinical language or cognitive impairments • Right handed • Seizures thought to have a focal source notin language areas • Electrode placements through language areas From supporting online material www.sciencemag.org/cgi/content/full/326/5951/445/DCI

  6. Electrode Placement

  7. Electrodes A & B During Surgery

  8. Electrode Locations Determined with Structural MRI Depths 1-6 along one probe

  9. Experimental Design

  10. Evidence of Relatively Normal Processing in Broca’s Area in These Patients Same paradigm & stimuli used with normal participants & these same patients in an fMRI study

  11. Relationship of fMRI Loci of Activity & Depth Probe Locations

  12. Grand Means Across All Conditions Triphasic response - Notice polarity reversals across channels - Means local generators

  13. Regional Specificity of Triphasic LFPs

  14. Response to Cue vs Target in Broca’s Area Response to cue not reliably modulated by experimental condition

  15. Evidence 1st Peak Reflects Lexical Processing - Amplitude reliably bigger for rarer words - But not reliably affected by word length - Peak time consistent w/ other estimates of word ID time

  16. Evidence 2nd Peak Reflects Inflectional Processing Amplitude equally large for Null- & Overt-Inflection What else do 2 “inflection” conditions have in common?

  17. No Differences for InflectingNouns vs Verbs

  18. Evidence 3rd Peak Reflects Phonological Processing Amplitude larger in Overt-Inflection

  19. Additional Evidence 3rd Peak Reflects Phonological Processing Amplitude larger for longer words

  20. Consistency of 1st peak of triphasic response across participants From supporting online material www.sciencemag.org/cgi/content/full/326/5951/445/DCI

  21. Consistency of 2nd peak of triphasic response across paticipants - Notice differences in - Amplitude scales - Electrode channels - Polarity From supporting online material www.sciencemag.org/cgi/content/full/326/5951/445/DCI

  22. Consistency of 3rd peak of triphasic response across participants - Notice different channels than previous figure From supporting online material www.sciencemag.org/cgi/content/full/326/5951/445/DCI

  23. Localizing Generators (Equivalent Current Dipole [ECD] Modeling)

  24. Conclusions • Processing a word for production • (in these hybrid comp/prod tasks) • Consists of sequentially ordered processes • Originating in spatially close but distinct regions in Broca’s area • Argue that this provides better support for • Language production models that have discrete non-interactive stages for different components of production • e.g. Levelt, Roelofs, & Meyer • Over models that incorporate interaction & feedback • e.g., Dell; Goldrick

  25. Conclusions • Stronger conclusion than warranted by data • Online response from Goldrick, Dell, Kroll, & Rapp “…full discreteness claim is not required by the Sahin et al. data and conflicts with an extensive body of research that has already demonstrated its inadequacy. … To account for the inadequacy of both fully discrete and fully interactive theories, language production models must allow for interaction while incorporating critical constraints on the degree of coupling between processing components. Such architectures respect the sequentiality of processing different types of information (in line with Sahin et al.’s results) without sacrificing the ability to account for interactive effects. Rather than viewing results such as those of Sahin et al.’s through a Boolean lens – supporting either fully interactive or fully discrete models – a more profitable approach would acknowledge the continuum of possibilities between these extremes.”

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