Seminar On The Topic:
“MagnetoEncephaloGraphy”
In this Presentation of mine; I’ll introduce you regarding-
 M.E.G.- Overv...
Just An Overiew….. What Actually It Is…??
MagnetoenCephaloGraphy (MEG)
is a technique for mapping brain
activity by recor...
V
Skull
CSF
Tissue
MEG
EEG
B
- Non-Invasive Measurement.
- Direct Measurement.
Scalp
Recording
Surface
Current
Flow.
Orien...
Actual Phenomenon:
 Currents in Neurons create very tiny Magnetic
Fields.
 MEG uses SQUIDs to detect these Magnetic
Fiel...
Entire Setup of the Process
S.Q.U.I.D.S….
 Superconducting Quantum
Interference Devices.
 Superconducting material is
niobium or lead alloy with
Gol...
Axial Gradiometer
Recording Surface
Neuronal Source
Capturing The Signal:
 For a gradiometer of this type, a
signal from ...
Josephson Junctions
 Two superconductors separated by a thin insulating
barrier:
 A small current will tunnel across the...
Detecting Brain Activity
 50,000 neurons need to fire to generate a
Readable signal.
 Neurons near the outside of the br...
Magnetic Shielding
 Rooms for MEGs have walls made of Aluminum and
MU-metal (a type of nickel-iron alloy with extremely
h...
Let The Pictures
Speak:
Sensor layout: recording from 160 channels
Response peak at 98ms after onset of an auditory stimulus,
in the left and righ...
What is the benefit of using MEG?
EEG
MEG
-As high temporal resolution as EEG …
… but much easier and quicker to set up (k...
 MEGs are used in research to measure the
time course of brain activity.
 MEGs can detect Epilepsy, as well as detect
ar...
MEG is a technique that allows you to
(i) record brain activity directly, with
excellent temporal resolution (ms)
(ii) des...
THANK YOU ALL..
Presented By:
Anuj Malik.
Roll No. MT-2112607
[E.E.E.] M.Tech.
FOR YOURS PRECIOUS
TIME....
Any
Query
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MagnetoEncephaloGraphy- By Anuj Malik

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MagnetoenCephaloGraphy (MEG) is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.

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  • @Cécile Gal the reference Link for 3rd Slide: etheses.whiterose.ac.uk/2407/1/Clarke_thesis_final.pdf
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  • Hi Anuj. Thank you for sharing your presentation! I would be interested in knowing the references for the schemes you show on your third slide. Do you have them? Thank you!
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MagnetoEncephaloGraphy- By Anuj Malik

  1. 1. Seminar On The Topic: “MagnetoEncephaloGraphy” In this Presentation of mine; I’ll introduce you regarding-  M.E.G.- Overview.  Origin of the Signal.  Entire Setup of the Process.  S.Q.U.I.D.S.  JosephSon Junctions.  Detecting Brain Activity.  Magnetic Shielding.  Benefits of Employing this Technology.  Future Scope of M.E.G. Technology.
  2. 2. Just An Overiew….. What Actually It Is…?? MagnetoenCephaloGraphy (MEG) is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.  M.E.G. Signals were first measured using a copper induction coil as the detector.
  3. 3. V Skull CSF Tissue MEG EEG B - Non-Invasive Measurement. - Direct Measurement. Scalp Recording Surface Current Flow. Orientation of Magnetic Field. Origin of the signal
  4. 4. Actual Phenomenon:  Currents in Neurons create very tiny Magnetic Fields.  MEG uses SQUIDs to detect these Magnetic Fields.  Magnetic Signals from the brain are only a few fT in strength.  Needs a Magnetically Shielded Room.
  5. 5. Entire Setup of the Process
  6. 6. S.Q.U.I.D.S….  Superconducting Quantum Interference Devices.  Superconducting material is niobium or lead alloy with Gold/Indium.  Cooled to low temperature with either liquid He (4K) or N (77K).  Manufactured at NIST in Boulder.  Noise levels about 3fT*Hz(-1/2).
  7. 7. Axial Gradiometer Recording Surface Neuronal Source Capturing The Signal:  For a gradiometer of this type, a signal from cortex looks different between the two coils because of the distance between the two coils.  A signal from far away, however, will look similar in size to the two coils.  This gradiometer principle can help further with the challenging problem of measuring small source that exist in an electro-magnetic environment with many large source (subways, elevators,computers, etc.).
  8. 8. Josephson Junctions  Two superconductors separated by a thin insulating barrier:  A small current will tunnel across the barrier:  The constant current Ic depends on temperature and magnetic field.  SQUIDS measure fractions of the phase difference in terms of the flux quantum h/2e.
  9. 9. Detecting Brain Activity  50,000 neurons need to fire to generate a Readable signal.  Neurons near the outside of the brain generate the strongest signals.
  10. 10. Magnetic Shielding  Rooms for MEGs have walls made of Aluminum and MU-metal (a type of nickel-iron alloy with extremely high magnetic permeability).  Aluminum shields from high frequency Noise.  MU-metal shields from low frequency noise.
  11. 11. Let The Pictures Speak:
  12. 12. Sensor layout: recording from 160 channels Response peak at 98ms after onset of an auditory stimulus, in the left and right temporal lobes.
  13. 13. What is the benefit of using MEG? EEG MEG -As high temporal resolution as EEG … … but much easier and quicker to set up (kids, patients) -Magnetic fields are not differentially attenuated …. …. easier to get a reasonable estimate of source over time. - Sensitivity to within-subjects effects.
  14. 14.  MEGs are used in research to measure the time course of brain activity.  MEGs can detect Epilepsy, as well as detect areas of the brain that are most important to avoid during surgery.  Does not depend on head geometry like EEG.  Magnetic fields decay faster over distance than electric fields. Few Other Notable PointS-
  15. 15. MEG is a technique that allows you to (i) record brain activity directly, with excellent temporal resolution (ms) (ii) design within-subjects experiments and evaluate single-subject data (iii) test models of cognitive processes and evaluate how these models map on to the brain. SummmariSation:
  16. 16. THANK YOU ALL.. Presented By: Anuj Malik. Roll No. MT-2112607 [E.E.E.] M.Tech. FOR YOURS PRECIOUS TIME.... Any Query
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