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Default Mode Network

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DMN, Smell, Memory. Default Mode Network. Blood Oxygen Level Dependent (BOLD) fMRI ... Studies have convincingly shown that with administration of physostigmine (an ... – PowerPoint PPT presentation

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Title: Default Mode Network


1
Default Mode Network
  • David Jones
  • Georgetown University Department of Medicine

2
Neuromodulators, Neurotransmitters, and Neural
Ensembles
  • Dopamine and Schizophrenia
  • Hypofrontality on fMRI
  • DMN, Smell, Memory

3
Default Mode Network
4
Blood Oxygen Level Dependent (BOLD) fMRI
  • Diamagnetic, Paramagnetic, and Ferromagnetic
  • Deoxyhemoglobin is paramagnetic
  • Oxyhemoglobin is diamagnetic
  • Field Inhomogeneities

5
Hemodynamic Response Function
6
BOLD Excitation vs. Inhibition
  • Recent studies into the relative metabolic demand
    of inhibition and excitation and their effect on
    BOLD signal have concluded that inhibition is far
    less metabolically demanding than excitation
    (Waldvogel et al).

7
Acetylcholine
  • Studies have convincingly shown that with
    administration of physostigmine (an
    acetylcholinesterase inhibitor) to healthy
    controls and Alzheimers Disease patients, there
    is a decrement in brain glucose consumption as
    measured by PET scanning after administration of
    isotope labeled glucose (Blin et al).
  • Other studies showed a decrease in rCBF, using
    isotope labeled water and PET scanning, with
    administration of physostigmine (Furey et al).
  • BOLD deactivations with physostigmine
    administration

8
Acetylcholine and Executive Function
  • The role that acetylcholine plays in different
    executive functions is not precisely known.
  • However, it has been most convincingly associated
    with attention, perceptual discrimination,
    spatial processing, and memory encoding.

9
How can I look at the DMN and acetylcholine?
  • Chemical Shift Imaging another type of fMRI that
    can look at molecules.
  • Signal acquisition times on the order of hours
  • New Technique SENSE-PEPSI can obtain data on the
    order of seconds.
  • Correlation Between BOLD Deactivations and
    Acetylcholine Neurotransmission as Measured by
    Change in Choline Peak Obtained Via SENSE-PEPSI
    An Event-Related fMRI Feasibility Study

10
Thanks
  • My mentor Dr. John VanMeter, the Georgetown
    Center for Functional and Molecular Imaging, and
    the GUMC General Clinical Research Center

11
References
  • Waldvogel, D., van Gelderen, P., Muellbacher, W.,
    Ziemann, U., Immisch, I., Hallett, M. 2000 The
    relative metabolic demand of inhibition and
    excitation. Nature 406, 995-998.
  • Furey, M.L., Pietrini, P., Haxby, J.V.,
    Alexander, G.E., Lee, H.C., VanMeter, J., Grady,
    C.L., Shelty, S.I., Rapoport, S.I., Schapiro,
    M.B., Freo, U. 1997 Cholinergic stimulation
    alters performance and task-specific regional
    cerebral blood flow during working memory. PNAS
    94, 6512-6516.
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