Neuroimaging

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Neuroimaging
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Spatial resolution the localization capability
of the method, ranging from individual synapses
to the brain as a whole. Temporal resolution
the time scale over which the method can take
measurements, ranging from milliseconds to
life-times.
Gazzaniga, M. S., Mangun, G. Ivry, R. (1998).
Cognitive Neuroscience The Biology of the Mind.
New York W.W. Norton.
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How to Select Which Method to Use
The method of choice depends on the scientific
question being asked. For neuronal activity, at
a cellular level, use single- or multi-unit
recording. For questions of structure, use CT or
MRI. For questions of function, or system
interactions, where the anatomy is of interest,
use PET, or fMRI. For questions of processing,
where timing is important, use ERP and/or MEG.
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Single- Multi-unit Recording
Invasive implanting an electrode into the
brain Passive recording the activity (action
potentials) of one or more neurons, not
stimulating activity Usually only done with
animals or people requiring neurosurgery
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Event-Related Potential (ERP)
128 Channel Cap
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Event-Related Potential (ERP)

• Brief changes in EEG signal
• Time-aligned with stimulus onset
• Averaged over 100s of responses
• Excellent temporal resolution
• Terrible spatial resolution

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ERP - waveforms topological maps
Evans, M. A., Shedden, J. M., Hevenor, S. J.
Hahn, M. C. (2000). The effect of variability of
unattended information on global and local
processing evidence for lateralization at early
stages of processing. Neuropsychologia, 38 (3),
225-239.
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Magnoencephalography (MEG)
151 Channel MEG
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Magnoencephalography (MEG)

• Current flow in neurons creates local magnetic
  fields
• MEG measures local magnetic field changes from
  the
• surface of the scalp using superconducting
  coils or
• SQUIDs
• Excellent temporal resolution
• Better spatial resolution than ERP

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MRI vs MEG
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CT or CAT scan(Computed Tomography)
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CT or CAT scan
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Positron Emission Tomography (PET)
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Physics of PET
Cherry, S. R. Phelps, M. E. (1996) Imaging
brain function with positron emission tomography.
In A. W. Toga J. C. Maxxiotta (Eds.),
Brain Mapping The Methods (pp. 191-221).
Toronto, ON Academic Press.
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PET images - radioactive isotopes
FDG or F18 fluorodeoxyglucose
O15 Water
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PET images
At Rest
Visual Stimulus
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Basic PET Analysis
Cherry, S. R. Phelps, M. E. (1996) Imaging
brain function with positron emission tomography.
In A. W. Toga J. C. Maxxiotta (Eds.),
Brain Mapping The Methods (pp. 191-221).
Toronto, ON Academic Press.
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Magnetic Resonance Imaging (MRI)
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MRI Physics
Brown, M. A. Semelka, R. C. (1999). MRI Basic
Principles and Applications. (2nd ed.). New York
John Wiley Sons.
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MRI Physics
Brown, M. A. Semelka, R. C. (1999). MRI Basic
Principles and Applications. (2nd ed.). New York
John Wiley Sons.
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Functional MRI (fMRI)

• Sources of Variance or Noise
• Physiological
• Cardiac pulsation
• Respiration
• Response fatigue
• Experimental
• Subject motion
• Environmental noise
• Instrumental
• Electrical instability
• Electrical noise
• Vibration

• Other data analysis issues
• Spatial normalization
• Spatial smoothing
• Partial voluming
• Susceptibility artifact

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fMRI - signal changes across time
Cohen, M. S. (1996)Rapid MRI and functional
applications. In A. W. Toga J. C. Maxxiotta
(Eds.), Brain Mapping The Methods (pp.
223-255). Toronto, ON Academic Press.
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Fossati, P., Hevenor, S. J., Lepage, M., Graham,
S. J., Grady, C., Keightley, M. L., Craik, F.
Mayberg, H. (2004). Distributed self in
episodic memory neural correlates of successful
retrieval of self-encoded positive and negative
personality traits. NeuroImage, 22 (4),
1596-1604.
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And Thats All She Wrote!