MEG Flashcards
What is MEG
Functional imaging technique that measures synchronous activity at the cortical layer of cortical neurones
What is a squid
Squid’s are semi conductor quantum interfering device
Squids measure the magnetic field
Helium at -269 degrees makes squid becomes super sensitive conductors
Due to lack of liquid helium globally new squids are being built around this
What is MEG magnetic field measured in
fento-Tesla
Where does MEG signal come from?
Comes from the cortical neurones which align in the cortex
MEG pros?
Excellent Temporal resolution
Good spatial resolution when paired with MRI
The inverse problem:
Depending on where you put the electrode there can be slight differences in charges of the dipole
Folds in the cortex may have aligned differences and can be an infinite amount of sources
Beamfoemers
Used to get the neuronal signal at point of interest
There are multiple sensors from m1-m5 which is weighted in voxels
This is a weighted sum of MEG of each virtual electrode
How is MEG data is analysed?
Drawing of the head is taken and features are ;located such as the skull, motor cortex and eyes
MEG sensor data and co registration are put over each other to derive a graph theory
Calculation of adjacency matrix is then done
MEG study
zolpidem drug is given to a stroke patient where MEG, MRI and MRS is taken
There was increased blood flow in certain areas of the brain
MRI showed dead tissue in the brain
MEG showed low activity state in healthy tissue
At the dead tissue site there was pathological oscillation with large amplitude
zolpidem decreased amplitude in pathological oscillation(around 40 minutes to activate drug)
What is functional mapping?
When stimulation occurs and an evoked responses localised with a cursor(can also be used to localise language function)
Advantages of MEG
Direct approach Non invasive No distortion of signals Short preparation time Near real time
