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EE 4BD4 Lecture 11

EE 4BD4 Lecture 11. The Brain and EEG. Brain Wave Recordings. Recorded extra-cellularly from scalp (EEG) Recorded from extra-cellularly from surface of cortex (ECOG) Recorded extra-cellularly from deep structures (electroneurogram). Brain Features. Cortical Fibres. Overview (EEG).

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EE 4BD4 Lecture 11

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  1. EE 4BD4 Lecture 11 The Brain and EEG

  2. Brain Wave Recordings • Recorded extra-cellularly from scalp (EEG) • Recorded from extra-cellularly from surface of cortex (ECOG) • Recorded extra-cellularly from deep structures (electroneurogram)

  3. Brain Features

  4. Cortical Fibres

  5. Overview (EEG)

  6. Cortical Contributions

  7. Electrode Placement

  8. Amplifier Connections

  9. Clinical Applications (Spontaneous EEG) • Identify presence of lesions (historical) • Diagnosis and monitoring of epilepsy (seizures) • Sleep staging • Estimation of depth of anesthesia • Other organic brain disease • Neuropsychiatry (depression, schizophrenia, Altzheimer)

  10. Cortical Electrodes

  11. Alpha Predominance

  12. General Bandwidths

  13. Abnormal Rythms

  14. Closed Loop Epilepsy Treatment

  15. EEG during REM Sleep

  16. EEG during Stage 3 Sleep

  17. Additional Sleep Data Processing • Sleep spindles (modulated alpha periods) and K complexes in Stage 1 – 2 • Degree of correlation (time base) or coherence (frequency base) between different channels of EEG increases with depth of sleep. • Higher level signal processing? • Relate EEG to other recorded data (e.g. respiration rate, heart rate, SaO2

  18. Brain Evoked Potentials

  19. Signal Pathway

  20. Other Evoked PotentialsrTMS: Repetitive Trans-Cranial Magnetic Stimulation • Treat severely depressed patients who are resistant to pharmacology • Alternative is periodic applications of electro-shock (ECT) treatment • 30% of patients respond • Would like to increase percentage of responders

  21. Current Commercial Machines • Example Magstim

  22. Clinical Treatment

  23. Stimulus Waveforms

  24. Magnetic Field Source: Medtronic, 2004 Source: Medtronic, 2004 Source: Medtronic, 2004

  25. Instrumentation Challenges Recording Simultaneous Evoked Potentials • Large magnetic field saturates electronics (coupling into electrode cable, amplifier inputs) • Signals very small plus other background EEG, need repetitive stimulation for treatment and averaging • Electrode heating during multiple stimuli • Stimulation of scalp muscles (mV amplitudes phase locked to responses) • Auditory “click” response

  26. Electrode Materials 3s at 20Hz at 85% intensity, r = -30mm

  27. rTMS Trains of Stimuli Au electrode, 3s at 20Hz at 85% intensity, trains at 0, 60, 120s

  28. Systems Approach

  29. Sham Response to rTMS “Clicks”

  30. Muscle Responses during 10 Hz Left-sided Stimulation

  31. Results of Day 2 Position Study (Typical Subject)

  32. Using Digital Filtering

  33. Using Wavelet Denoising

  34. Brain Response for Sensitive Subject

  35. Wavelet Denoised Response

  36. Right side 1 Hz Response

  37. Right Side Denoised Response

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