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NIMH MEG Core FacilityMagnetoencephalography Imaging Resource, IRP, NIMH / NINDS
Comparison of temporal and spatial resolution for various neuroimaging methods.
At a comparable p level threshold the MEG for a window around the response showed beta desynchronization with a very similar spatial extent to the BOLD activation. This relationship will be important for better understanding of the physiological basis of neuroimaging activation.
BOLD fMRI was collected at 3T with an identical task design. Data were structurally aligned, smoothed, and MNI normalized using SPM99. Single subject contrast maps for 2-back > 0-back were followed by a group analysis.
System Overview
Comparison to fMRI
Resources
Basic Concepts
Pre-Processing
Filtering / Adding Markers
The MEG Core Facility website (http://kurage.nimh.nih.gov/) provides information and scheduling to the user community. The site includes user guidelines and training plans, manuals, tutorials, as well as forms for requesting access, user accounts and scheduling as well as software and scripts for data processing.
Contact information: Dr. Richard Coppola, Director [email protected]
Dr. Tom Holroyd, Staff Scientist [email protected]
The MEG Core Facility is resource serving the intramural research programs of the NIMH and NINDS for IRP investigators to perform functional neuroimaging studies to further the understanding of healthy and diseased brain function and physiology. The facility provides a complete environment for stimulus presentation, monitoring and recording subject behavior and physiology while recording magnetoencephalographic data.
Facility Description
Co-Registering with MRI
Head Coils placed on Fiducials
User Information
Group Analysis (SUMA)
• MRI’s Talairach aligned in AFNI
• SAM image z-score normalized by pooled variance
• AFNI 3dMean averages warped SAM volumes
• Normalized t-statistic (3dttest) to threshold group mean map
The core operates a CTF OMEGA whole head MEG system (275 MEG and 64 EEG channels) from VSM MedTech. Services include providing for temporary data storage, data transfer, instruction on running the instruments, as well as aid with signal processing and analysis.
Data Processing
Obtain Protocol Approval• Users are required to have an NIH IRB-approved protocol
describing the intended MEG research. Request a User Account• A Facility Access Request form must be filled out to establish a
user account.• The account will give access to the scheduling calendar and also
provide access to the MEG Core Facility data storage system.Attend MEG Orientation• New users will be given a tour of the facility, at which time the
operation of the scanner, facility rules, etc., will be discussed. • Staff can discuss in detail Issues related to experimental design,
data analysis, Experiment Setup / Piloting• The MEG Core Facility Staff can assist users in task design,
programming, and other aspects of actually running the experiment.
Time-Frequency Analysis using the Stockwell Transform
Gamma Sources
Time resolution of MEG allows for detailed frequency response analysis of a five auditory click experiment.
MEG and fMRI2-back vs 0-back comparison same 12 subjects group map at p approx < .001
SPM T map 2b>0b {SPM99 t ~ 4.0; Z ~ 3.10, p ~ 0.001, k > 10}
SAM 500 msec window on responseBeta desynchronization (left = right)
MEG's primary response is to tangential fields, whereas EEG can be used to measure radial fields. Furthermore, MEG signals are the result of intracellular currents while EEG measures volume/extracellular currents. The information that is provided by these two measures is complementary.
A close group of neurons can act as a single current source, which in turn gives rise to a magnetic field over the surface of the head.
Stimuli / Response
• Visual projector
• Stereo audio
• Somatosensory
• 4 & 5 button response pads – two hands
• X-Y joystick
• Eye movement monitor
Task Development
• Presentation (Neurobehavioral Systems)
• Psychophysics toolbox for MATLAB
• E-Prime (Psychology Software Distribution)
• SuperLab Pro
• Windows 98 or XP
Event Related Fields
Auditory N100m
Recent Studies
Dual-State Beamformer Imaging using SAMimg
MEG dataMEG data
bandpass filter
bandpass filter
ROIROI
beamformeractive power
beamformeractive power
parse data
parse data
state timingstate timing
active covariance
active covariance
control covariance
control covariance
beamformercontrol power
beamformercontrol power
differenceor
ratio
differenceor
ratio
display imagedisplay image
for each voxel…
Time-course of cortical activation relative to response for 2-back vs 0-back
Biol Psychiatry. 2009 February 15;65(4): 289-295.
Brain Res. 2008 Dec 9;1244:103-12.
Fiducial points marked on MRI using AFNI
