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Methods

Methods. Neuropsychology Lesion data Single dissociation Double dissociation Transcranial magnetic stimulation (TMS). TMS. Electrical current sent through coil generates a magnetic field that passes through the scalp, depolarizes neuronal membrane, and causes action potential. TMS. TMS.

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Methods

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  1. Methods • Neuropsychology • Lesion data • Single dissociation • Double dissociation • Transcranial magnetic stimulation (TMS)

  2. TMS • Electrical current sent through coil generates a magnetic field that passes through the scalp, depolarizes neuronal membrane, and causes action potential

  3. TMS

  4. TMS • Electrical current sent through coil generates a magnetic field that passes through the scalp, depolarizes neuronal membrane, and causes action potential • Depending on timing, frequency, intensity, and angle of stimulation, • Decrease cortical excitability • Way to create a temporary “lesion” in particular brain area (e.g., Fuggettaet al., 2008) • Increase cortical excitability • Way to temporarily enhance function of particular brain area (e.g., Willems et al., 2011)

  5. Fuggetta et al. (2008) • Examine role of middle temporal area in noun comprehension • “Lesioned” area using TMS • Left middle temporal, right middle temporal, middle occipital, no TMS • Examined comprehension performance • Picture-word matching

  6. Fuggetta et al. (2008)

  7. Fuggetta et al. (2008) • Examine role of middle temporal area in noun comprehension • “Lesioned” area using TMS • Left middle temporal, right middle temporal, middle occipital, no TMS • Examined comprehension performance • Picture-word matching • Living (natural) vs. non-living (artifactual) items

  8. Fuggetta et al. (2008) Left Middle Temporal Right Middle Temporal Middle Occipital No TMS

  9. Fuggetta et al. (2008) • Examine role of middle temporal area in noun comprehension • “Lesioned” area using TMS • Left middle temporal, right middle temporal, middle occipital, no TMS • Examined comprehension performance • Picture-word matching • Living (natural) vs. non-living (artifactual) items • Important for non-living categorization • What about living items? • Anterior-temporal poles are challenging • TMS only affects regions close to surface

  10. Willems et al. (2011) • Examined role of premotor cortex in verb processing • Stimulated hand area in left and right premotor cortex using TMS • Left premotor cortex helps plan actions of right hand • Right-handed subjects decided whether letter strings formed real words or not (e.g., throw vs. wroth) • Lexical-decision task • Verbs were either manual (e.g., throw, write) or non-manual (e.g., earn, wander)

  11. Willems et al. (2011)

  12. Willems et al. (2011)

  13. Willems et al. (2011) • Examined role of premotor cortex in verb processing • Stimulated hand area in left and right premotor cortex using TMS • Left premotor cortex plans actions of right hand • Right-handed subjects decided whether letter strings formed real words or not (e.g., throw vs. wroth) • Lexical-decision task • Verbs were either manual (e.g., throw, write) or non-manual (e.g., earn, wander) • Hand region in premotor cortex is involved in manual action processing

  14. Methods • Neuropsychology • Lesion data • Single dissociation • Double dissociation • Transcranial magnetic stimulation (TMS) • Temporarily increase/decrease cortical excitability • Used to assess the role of particular brain regions in particular mental functions • Used in clinical settings to help alleviate depression and chronic pain

  15. Methods • Magnetic resonance imaging (MRI)

  16. MRI Scanner

  17. Strong Magnet

  18. Strong Magnet • Earth’s magnetic field = 0.5 Gauss • 1 Tesla (T) = 10,000 Gauss • 3 Tesla = 3 x 10,000  0.5 = 60,000 x Earth’s magnetic field

  19. Strong Magnet

  20. MRI • Hydrogen atoms are prevalent in brain • Protons forming nucleus spin around their principle axis and create tiny magnetic field • Proton orientation is randomly distributed • Powerful magnetic force aligns protons • Radio waves perturb orientation in predictable direction

  21. Protons (In Hydrogen Atoms)

  22. MRI • When radio wave turned off, protons realign with magnet • Rebound is measured by detectors surrounding head • Different magnetic agents such as protons rebound at different rates • Reconstruct image reflecting distribution of protons and other magnetic agents • More protons in gray than white matter

  23. 2-D Images in Single Plane

  24. Reconstructed for 3-D Horizontal [Axial, Transverse] Coronal Sagittal

  25. Methods • Magnetic resonance imaging (MRI) • Voxel-based morphometry • Courchesneet al. (2000) • Diffusion tensor imaging (DTI)

  26. DTI • Uses traditional MRI scanner • Measures motion of water in axons • Motion is anisotropic (restricted by myelin) • More likely to flow in direction of axon than perpendicular to axon • Can be used to image axonal connections in brain

  27. Fronto-Occipital Fasciculus

  28. Arcuate Fasciculus Broca’s area X X

  29. Arcuate Fasciculus Anterior  posterior Inferior  superior Medial  lateral

  30. Rilling et al. (2008) Human Chimpanzee Macaque

  31. Methods • Magnetic resonance imaging (MRI) • Voxel-based morphometry • Courchesneet al. (2000) • Diffusion tensor imaging (DTI) • Image axonal connections

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