SAM Source Analysis SAM: Synthetic Aperture Magnetometry Optimum spatial filter for each voxel calculated from dual state time- domain covariance matrix NIMH MEG Core Facility Magnetoencephalography Imaging Resource, IRP, NIMH / NINDS Comparison of temporal and spatial resolution for various neuroimaging methods. Of the 12 SAM maps (4 frequency bands by 3 time windows) only the beta band for the response window showed very high agreement with the BOLD activation. At a comparable p level threshold the MEG 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 (GE EPI-RT) with an identical task design. Data were structurally aligned, smoothed, and normalized to MNI space using SPM99. Single subject block design contrast maps for 2-back > 0-back were followed by a group second level analysis and thresholded at approximately p<.001. This map showed activation of the working memory network as described in several studies. System Overview Comparison to fMRI Resources Basic Concepts Data Collection Pre-Processing Filtering / Adding Markers The MEG Core Facility website ( has been set up to provide 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. This has been expanded to include considerable available software and scripts for data processing. Contact information: Dr. Richard Coppola, Director Dr. Tom Holroyd, Staff Scientist The MEG Core Facility is a core resource serving the intramural research programs of the National Institute of Mental Health (NIMH) and the National Institute for Neurological Disorders and Stroke (NINDS). Its function is to provide a resource 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 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 staff operates a CTF OMEGA whole head MEG system (275 MEG and 64 EEG channels) from VSM MedTech. Additional services include providing for temporary data storage, data transfer, instruction on running the instruments, as well as assistance with signal processing and analysis. The staff consists of a Facility Director, and four dedicated positions including senior Staff Scientist, System Analyst, post- bac IRTA, and an MEG Technologist. 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 users 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. Issues related to experimental design, data analysis, etc., are also open for discussion, and generally the staff will schedule a further meeting where these issues can be discussed in more detail. 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 Gamma Sources Fiducial points marked on MRI Time resolution of MEG allows for detailed frequency response analysis of a five auditory click experiment. MEG and fMRI 2-back vs 0-back memory task, Block design. 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 response Beta desynchronization (left = right) CBDB and NIMH MEG Core 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 Evoked Fields Auditory N100m