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Techniques in Cognitive Neuroscience Transcranial Magnetic Stimulation (TMS)

Techniques in Cognitive Neuroscience Transcranial Magnetic Stimulation (TMS). Example Exam Questions. How has transcranial magnetic stimulation advanced our understanding about the human brain?

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Techniques in Cognitive Neuroscience Transcranial Magnetic Stimulation (TMS)

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  1. Techniques in Cognitive NeuroscienceTranscranial Magnetic Stimulation (TMS)

  2. Example Exam Questions • How has transcranial magnetic stimulation advanced our understanding about the human brain? • What are the advantages and limitations of transcranial magnetic stimulation relative to other techniques used in cognitive neuroscience. • How does transcranial magnetic stimulation compare with other neuroscientific techniques with regard to spatial and temporal resolution? • “Transcranial magnetic stimulation allows the cognitive neuroscientist to manipulate brain function in time and space.” Discuss.

  3. Transcranial Magnetic StimulationLecture Outline • Neurophysiological Underpinnings • Applications • Research • Diagnostic • Therapeutic • Advantages • Limitations

  4. Transcranial Magnetic StimulationNeurophysiological Underpinnings Electromagnetic induction: An electric current passed through a stimulating coil produces a magnetic field; changes in the magnetic field induces a flow of electric current in a nearby conductor – brain tissue.

  5. Transcranial Magnetic StimulationNeurophysiological Underpinnings Coil design: Circular coil stimulation induces a brain current running in the opposite direction of the primary coil current; the induced current intensity is a function of distance from the stimulating coil. .

  6. Transcranial Magnetic StimulationNeurophysiological Underpinnings Coil design: In a Figure-8 (focal) coil, the coil current sums at the coil junction; The induced electric field lies parallel with the cortical surface; Must quantify “motor threshold [MT]” to determine standardised stimulation. .

  7. Transcranial Magnetic StimulationNeurophysiological Underpinnings

  8. Transcranial Magnetic StimulationNeurophysiological Underpinnings Coil positioning: Over the left primary motor cortex, the current in the coil flow must be counter-clockwise; this is likely related to the anatomical orientation of pyramidal tract neurons and their axons.

  9. Transcranial Magnetic StimulationNeurophysiological Underpinnings “Cortical silent period” illustrates a refractory phase following a stimulating pulse.

  10. Transcranial Magnetic StimulationNeurophysiological Underpinnings “Short interval intra-cortical inhibition (SICI) and facilitation (SICF)”: Subthreshold conditioning pulse activates GABA-ergic inhibitory interneurons… (Kujirai, 1993)

  11. Transcranial Magnetic StimulationNeurophysiological Underpinnings Psychoparmacology: GABA-ergic agonists increase the CSP… (Werhahn et al., 1999)

  12. Transcranial Magnetic StimulationNeurophysiological Underpinnings Psychoparmacology: … and ethanol reduces SICF of MEPs (Ziemann et al., 1995)

  13. Transcranial Magnetic StimulationNeurophysiological Underpinnings High-frequency Repetitive TMS (HF rTMS): Increases cortical excitability (Peinemann et al., 2004)

  14. Transcranial Magnetic StimulationApplications: Neuropsychology

  15. Transcranial Magnetic StimulationApplications: ...Neuropsychology

  16. Transcranial Magnetic StimulationApplications: “Virtual Lesions” (Desmurget et al., 1999)

  17. Transcranial Magnetic StimulationCombining Techniques: fMRI (Bestmann et al., 2005)

  18. Transcranial Magnetic StimulationCombining Techniques: EEG (Esser et al., 2006)

  19. Transcranial Magnetic StimulationAdvantages (Cowey & Walsh, 2000)

  20. Transcranial Magnetic StimulationLimitations Inter-individual variability: e.g. Skull thickness

  21. Transcranial Magnetic StimulationLimitations Intra-individual short-term variability

  22. The End

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