MEG Connectivity and Power Detections with Minimum Norm Estimates Require Different Regularization Parameters

Figure 3

Differences in MNE performance when using the optimal lambda found using the L-curve approach and the best lambda values obtained from our simulations. (a) Difference in performance using the L-curve and the empirically derived lambda for power (upper row) and coherence (lower row) ( indicates statistically significant differences at , -test). (b) Illustrative example of a simulated pair of coupled sources (alpha-band coherence = 0.4, patch size = 4 cm², and SNR = 0 dB). ((c) and (d)) Power and coherence reconstructions based on simulated data shown in panel (b) using three options for the definition of an optimal lambda value: (obtained with the L-curve), (mean optimal value for coherence detection), and (mean optimal value for power detection). Note that the power and coherence maps are normalized with respect to the maximum on each map and subsequently thresholded at 20% of maximum amplitude.