Brain Topography

, Volume 32, Issue 3, pp 363–393 | Cite as

Brain Activity Mapping from MEG Data via a Hierarchical Bayesian Algorithm with Automatic Depth Weighting

  • Daniela CalvettiEmail author
  • Annalisa Pascarella
  • Francesca Pitolli
  • Erkki Somersalo
  • Barbara Vantaggi
Original Paper


A recently proposed iterated alternating sequential (IAS) MEG inverse solver algorithm, based on the coupling of a hierarchical Bayesian model with computationally efficient Krylov subspace linear solver, has been shown to perform well for both superficial and deep brain sources. However, a systematic study of its ability to correctly identify active brain regions is still missing. We propose novel statistical protocols to quantify the performance of MEG inverse solvers, focusing in particular on how their accuracy and precision at identifying active brain regions. We use these protocols for a systematic study of the performance of the IAS MEG inverse solver, comparing it with three standard inversion methods, wMNE, dSPM, and sLORETA. To avoid the bias of anecdotal tests towards a particular algorithm, the proposed protocols are Monte Carlo sampling based, generating an ensemble of activity patches in each brain region identified in a given atlas. The performance in correctly identifying the active areas is measured by how much, on average, the reconstructed activity is concentrated in the brain region of the simulated active patch. The analysis is based on Bayes factors, interpreting the estimated current activity as data for testing the hypothesis that the active brain region is correctly identified, versus the hypothesis of any erroneous attribution. The methodology allows the presence of a single or several simultaneous activity regions, without assuming that the number of active regions is known. The testing protocols suggest that the IAS solver performs well with both with cortical and subcortical activity estimation.


MEG inverse problem Activity map Brain region Bayes factor Deep sources 



This work was completed during the visit of DC and ES at University of Rome “La Sapienza” (Visiting Researcher/Professor Grant 2015). The hospitality of the host university is kindly acknowledged. The work of ES was partly supported by NSF, Grant DMS-1312424. The work of DC was partially supported by grants from the Simons Foundation (#305322 and # 246665) and by NSF, Grant DMS-1522334.

Supplementary material

10548_2018_670_MOESM1_ESM.pdf (80 kb)
Supplementary material Figure S1 Mapping of the brain activity to 85 different BRs over 100 simulations using synthetic data corresponding to randomly generated activity patches in the right frontal pole, indicated in red in the list of the BRs reconstructed with, respectively, IAS (a), wMNE (b), dSPM (c) and sLORETA (d). The histograms bin the average activity in each BR: in red the BRs of the left hemisphere and in black the ones of the right hemisphere. (pdf 79.7KB)
10548_2018_670_MOESM2_ESM.pdf (80 kb)
Supplementary material Figure S2 Mapping of the brain activity to 85 different BRs over 100 simulations using synthetic data corresponding to randomly generated activity patches in the left amygdala, indicated in red in the list of the BRs reconstructed with, respectively, IAS (a), wMNE (b), dSPM (c) and sLORETA (d). The histograms bin the average activity in each BR: in red the BRs of the left hemisphere and in black the ones of the right hemisphere. (pdf 79.6KB)


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Mathematics, Applied Mathematics and StatisticsCase Western Reserve UniversityClevelandUSA
  2. 2.Istituto per le Applicazioni del Calcolo “Mauro Picone”CNR - National Research CouncilRomeItaly
  3. 3.Department of Basic and Applied Science for EngineeringUniversity of Rome “La Sapienza”RomeItaly

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