Transcript Magnetoencephalography, Really Fast Fourier Transforms, and the Hunt for HFOs William F. Eddy Department of Statistics Machine Learning Biological Sciences Carnegie Mellon University Pittsburgh, PA [email protected] Bagic, 2006

Magnetoencephalography,
Really Fast Fourier Transforms,
and the Hunt for HFOs
William F. Eddy
Department of Statistics
Machine Learning
Biological Sciences
Carnegie Mellon University
Pittsburgh, PA
[email protected]
Bagic, 2006
Special Thanks
• Anto Bagic, MD, Director CABMSI,UPMC
• Anna Haridis, MBA,MEG Coordinator,UPMC
• Jianming Wang, Ph.D., Tianjin University, PRC
• Bronwyn Woods, Graduate Student, CMU Neural
Computation
• Shuhei Okamura, Graduate Student,CMU Statistics
• Erika Taylor, Graduate Student, CMU Psychology
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Outline
• Magnetoencephalography
• Fourier Transforms
• High Frequency Oscillations
• Success/Failure
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http://www.4dneuroimaging.com
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MEG
• MEG is most powerful technique for studying brain
function non-invasively
• MEG records magnetic fields induced by synchronized
neuronal activity seen outside of the skull
• MEG can attain a temporal resolution of a few
milliseconds.
• MEG can monitor the activation of a neuronal population
with a spatial resolution of several millimeters
(Cohen, 1972; Hamalainen et al., 1993; George et al., 1995; Vrba & Robinson, 2001; Pataraia et al.,2002).
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Gradiometer & Magnetometer
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Magnetically Shielded Room
(Cohen et al., 2002)
Image Courtesy of Elekta
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Head
measurement
Nasion
EEG Cap
EOG Electrodes
RPA, LPA
Digitization
Finally!
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Magnetic Field Measurements
• Frequency:
– 10 mHz (as low as 1 mHz for sleep spindles) to 1 kHz.
• Field magnitudes:
– ~10 fT (10-15 T) for spinal cord signals to about a
picotesla (10-12 T) for brain rhythms.
• The Earth ~ 0.5 mT, the urban magnetic noise ~ 1
nT – 1 T.
• The Environment/Brain Ratio: 1 million – 1 billion.
(Nakaya & Mori, 1992; Vrba & Robinson, 2001)
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