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Comparative Study
. 2004 Nov 30:2004:52.

NUTMEG: a neuromagnetic source reconstruction toolbox

S S Dalal  1 , J M Zumer, V Agrawal, K E Hild, K Sekihara, S S Nagarajan
Affiliations
Comparative Study

NUTMEG: a neuromagnetic source reconstruction toolbox

S S Dalal et al. Neurol Clin Neurophysiol. .

Abstract

We have developed an analysis toolbox called NUTMEG (Neurodynamic Utility Toolbox for Magnetoencephalography) for reconstructing the spatiotemporal dynamics of neural activations and overlaying them onto structural MR images. The toolbox runs under MATLAB in conjunction with SPM2 and can be used with the Linux/UNIX, Mac OS X, and even Windows platforms. Currently, evoked magnetic field data from 4-D Neuroimaging, CTF, and KIT systems can be imported to the toolbox for analysis. NUTMEG uses an eigenspace vector beamforming algorithm to generate a tomographic reconstruction of spatiotemporal magnetic source activity over selected time intervals and spatial regions. The MEG coordinate frame is coregistered with an anatomical MR image using fiducial locations and, optionally, head shape information. This allows the reconstruction to be superimposed onto an MRI to provide a convenient visual correspondence to neuroanatomy. Navigating through the MR volume automatically updates the displayed time series of activation for the selected voxel. Animations can also be generated to view the evolution of neural activity over time. Since NUTMEG displays activations using SPM2's engine, certain SPM functions such as brain rendering and spatial normalization may be applied as well. Finally, as a MATLAB package, the end user can easily add customized functions. Source code is available at http://bil.ucsf.edu/ and distributed under a BSD-style license.

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Figures

Figure 1
Figure 1
Interactive tool showing MEG sensor data (left) and singular values of the sensor covariance matrix (right) with associated eigenprojections (right, inset). The time interval and signal subspace desired for beamforming reconstruction can be selected here.
Figure 2
Figure 2
Interface for selecting volume of interest (VOI) for beamformer reconstruction. VOIs may be defined by drawing outlines on each of the three orthogonal cross-sections.
Figure 3
Figure 3
Beamformer reconstruction of evoked tactile stimulation of right D2 showing time series and localization for S1 at 66 ms (top) and S2 at 136 ms (bottom); note S2 also shows activity at 66 ms (slice has been tilted to include both S1 and S2). The peak at 20 ms is due to stimulus artifact.
See this image and copyright information in PMC

References

    1. Dalal SS, Zumer JM, Sekihara K, Nagarajan SS. Modified beamformers for coherent source region suppression [abstract]. In: Halgren E, Ahlfors SP, Hamalainen MS, Cohen D, editors. Proceedings of the 14th International Conference on Biomagnetism; Boston: Biomag; Boston, USA. 2004 Aug 8-12.2004. p. 488.
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    1. The Open Source Initiative The BSD License. 2004. http://www.opensource.org/licenses/bsd-license.php. http://www.opensource.org/licenses/bsd-license.php Available from: URL:
    1. Sahani M, Nagarajan SS. Reconstructing MEG sources with unknown correlations. In: Thrun S, Saul L, Scholkopf, editors. Advances in neural information processing systems 16. Cambridge: MIT Press; Cambridge, MA: 2004. in press.

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