swLORETA: a novel approach to robust source localization and synchronization tomography

Abstract

Standardized low-resolution brain electromagnetic tomography (sLORETA) is a widely used technique for source localization. However, this technique still has some limitations, especially under realistic noisy conditions and in the case of deep sources. To overcome these problems, we present here swLORETA, an improved version of sLORETA, obtained by incorporating a singular value decomposition-based lead field weighting. We show that the precision of the source localization can further be improved by a tomographic phase synchronization analysis based on swLORETA. The phase synchronization analysis turns out to be superior to a standard linear coherence analysis, since the latter cannot distinguish between real phase locking and signal mixing.

Assessment of mental workload: A new electrophysiological method based on intra-block averaging of ERP amplitudes

“…An improved version of standardized Low Resolution Electromagnetic Tomography incorporating a singular value decomposition-based lead field weighting (swLORETA) was used to estimate intracranial sources of the scalp-recorded data (Nazari et al, 2010;Palmero-Soler et al, 2007;Pascual-Marqui et al, 1994). Intracranial source localizations were estimated and statistically processed on average P3a and P3b measured at the time of the peak maximum over central electrodes using the ASA4 software (ANT).…”

Semantic brain areas are involved in gesture comprehension: An electrical neuroimaging study

“…distribution of neural electric activity that maximizes similarity (i.e., maximizes synchronization) in terms of orientation and strength between neighboring neuronal populations (represented by adjacent voxels). In this study, an improved version of standardized weighted low-resolution brain electromagnetic tomography (sLORETA) was used; this version incorporates a singular value decomposition-based lead field weighting (i.e., swLORETA, Palmero-Soler, Dolan, Hadamschek, & Tass, 2007). The source space properties included a grid spacing (the distance between two calculation points) of 5 points and an estimated signal-to-noise ratio, which defines the regularization, of 3 (higher values indicating less regularization and therefore less blurred results).…”

Functional integrity of thalamocortical circuits differentiates normal aging from mild cognitive impairment

“…The brain locations corresponding to these potentials were obtained using a 3D brain space. The activation probability of each grid element in this brain space was computed by the standardized weighted low-resolution brain electromagnetic tomography (swLORETA) [Palmero-Soler et al, 2007]. A realistic head model of three layers (scalp, skull and brain with conductivities of 0.33, 0.0042, and 0.33, respectively) was used for this purpose.…”