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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: Neurosurg Clin N Am. 2011 Apr;22(2):153–167. doi: 10.1016/j.nec.2010.11.006

Figure 7.

Figure 7

Localization of epileptic spikes. (A) Simultaneously acquired EEG (top) and MEG (bottom) signals from a patient with epilepsy. An epileptic spike is seen in MEG sensors over the right temporal and frontal regions. (B) An equivalent current dipole (ECD) computed at the peak of the spike (“0 ms”; the corresponding isocontour map of the MEG data, with the ECD as a green arrow, is shown at top left) is localized in the temporal lobe (blue dots superimposed on the anatomical MRI). (C) Distributed source estimates, the noise-normalized minimum-norm estimate (MNE), also known as dynamic statistical parametric map (dSPM), for the MEG data are displayed on the cortical surface representation reconstructed from anatomical MRI. The source estimates suggest that the activity propagates from a right temporal region (“0 ms”) to the right frontal region (“50 ms”). (D) Comparison of MEG data with intracranial EEG (iEEG). The left panel shows the estimated MEG source waveforms (MNE) at four locations (“1” and “2” temporal, “3” and “4” frontal). The right panel shows the iEEG of an epileptic spike at corresponding locations. The MEG and iEEG are consistent in suggesting temporal activity propagating to the frontal lobe over a 50 ms time period. [Figures created by Dr. Naoro Tanaka, M.D., Ph.D.]