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Test on Monday, 9/29

Test on Monday, 9/29. Lectures, Chapters 1, 3, 4, and 11 Multiple choice, fill-in-the-blank, short answer, long answer List of important concepts Monday, 9/22 Long -answer questions on Friday, 9/26. Functional Imaging. Electroencephalography (EEG) Event-related potentials (ERP)

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Test on Monday, 9/29

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  1. Test on Monday, 9/29 • Lectures, Chapters 1, 3, 4, and 11 • Multiple choice, fill-in-the-blank, short answer, long answer • List of important concepts Monday, 9/22 • Long-answer questions on Friday, 9/26

  2. Functional Imaging • Electroencephalography (EEG) • Event-related potentials (ERP) • Magnetoencephalography (MEG) • Positron emission tomography (PET) • Functional magnetic resonance imaging (fMRI)

  3. EEG • Electroencephalography • Neural activity is electromagnetic process • Electrical potentials from populations of active neurons are measured through the scalp

  4. EEG

  5. EEG

  6. EEG

  7. ERP • Event-related potential • Align EEG signal with an external event • Stimulus or response • Average over many trials of same type (variation cancels out)

  8. ERP

  9. ERP • Event-related potential • Align EEG signal with an external event • Stimulus or response • Average over many trials of same type (variation cancels out) • Identify relevant waveform(s) • N400 (negatively deflecting waveform occurring 400 ms post event [stimulus] onset) • Indicates unexpected (e.g., McLaughlin et al., 2004)

  10. 14 hrs 63 hrs 138 hrs McLaughlin et al. (2004)

  11. ERP • Event-related potential • Align EEG signal with an external event • Stimulus or response • Average over many trials of same type (variation cancels out) • Identify relevant waveform(s) • N400 (negatively deflecting waveform occurring 400 ms post event [stimulus] onset) • Indicates unexpected (e.g., McLaughlin et al., 2004) • P300 (positively deflecting waveform occurring 300 ms post event [stimulus] onset) • Indicates low-probability (oddball) event

  12. EEG / ERP • Good temporal resolution (milliseconds) • Poor spatial resolution • Where is electrical activity generated?

  13. EEG / ERP • Inverse problem • Infinite number of charge distributions could lead to same pattern on surface

  14. EEG / ERP • Inverse problem • Infinite number of charge distributions could lead to same pattern on surface • Inverse dipole modeling • Hypothesize dipole in sphere and determine the distribution of voltages it would project onto the sphere’s surface • Compare actual results with predicted

  15. EEG / ERP

  16. EEG / ERP • Inverse problem • Infinite number of charge distributions could lead to same pattern on surface • Inverse dipole modeling • Hypothesize dipole in sphere and determine the distribution of voltages it would project onto the sphere’s surface • Compare actual results with predicted • Improves spatial resolution • Even better if use MRI scan to create model

  17. MEG • Magnetoencephalography • Similar to EEG/ERP except measures changes in magnetic fields instead of changes in electricity • MEG traces aligned to event and averaged across trials • Event-related fields (ERFs) • Inverse dipole modeling • Solutions more accurate than for ERP because magnetic fields are not distorted as pass through brain, scull, and scalp

  18. MEG

  19. MEG

  20. PET • Positron emission tomography • Measures variations in cerebral blood flow • More active areas require more blood • Radioactive tracer (isotopes) injected into blood stream • Blood flows to active areas • As isotopes decay, gamma rays (photons) are released • Scanner detects photons • More in active areas

  21. PET

  22. PET • Takes about 10 minutes for tracer to leave body • Subject engage in one condition at a time (every 10 minutes) • Subtractions

  23. Petersen et al. (1988) • What brain areas are involved in language comprehension and production? • Four tasks performed (visual and auditory) • Resting (+) • Viewing/hearing word • Reading/repeating word • Using word • Three subtractions • Viewing/hearing – resting = sensory • Reading/repeating – viewing/hearing = output • Using – reading/repeating = association (comprehension)

  24. Subtractions - = Viewing words Resting (+) Word perception - = Reading words Viewing words Word production

  25. Petersen et al. (1988) • What areas are involved in language comprehension and production? • Four tasks performed (visual and auditory) • Resting (+) • Viewing/hearing word • Reading/repeating word • Using word • Three subtractions • Viewing/hearing – resting = sensory • Reading/repeating – viewing/hearing = output • Using – reading/repeating = association (comprehension)

  26. Left Hemisphere Visual Auditory Sensory Output Association

  27. Right Hemisphere Visual Auditory Sensory Output Association

  28. Hemisphere Asymmetry Left Right Visual Auditory Sensory Output Association

  29. PET • Takes about 10 minutes for tracer to leave body • Subject engage in one condition at a time (every 10 minutes) • Subtractions • Poor temporal resolution • Ok spatial resolution (~10 mm3) • Need MRI or CT scan for structure

  30. fMRI • Functional magnetic resonance imaging • Similar to MRI • Radio waves perturb proton orientation in predictable direction • When radio wave turned off, protons realign with magnet • Rebound is measured by detectors • Except focuses on protons in hemoglobin (instead of those in gray/white matter) • Oxygen-transport protein in blood • Blood oxygenation level-dependent (BOLD) signal

  31. fMRI • Good spatial resolution (~3 mm3) • Ok temporal resolution (seconds) Takes time to collect images (1-3 seconds)

  32. fMRI • Typical BOLD response

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