Minimum Norm

Non-regularized

Regularized

LORETA

Non-regularized

Regularized

Figure 2. LORETA and minimum norm images (non-regularized and regularized) corresponding to a test point source at Talairach coordinates (-3,-46,43). Noise was added to the scalp voltages (ratio of variances of signal to noise (SNR) equal to 10). Regularization was estimated via minimum cross-validation error. Anatomy is coded in black to white. Estimated current density in cortical grey matter is coded white (zero) to red (maximum). Location of maximum activity is indicated numerically and by black triangles on the coordinate axes. Estimated maximum strength is indicated numerically (single number following Talairach coordinates). Exact localization (with blurring) is achieved only with regularized LORETA. Other notation: (L=left; R=right; A=anterior; P=posterior).