title: Maximum-likelihood estimation of low-rank signals for multiepoch MEG/EEG analysis.
abstract: A maximum-likelihood-based algorithm is presented for reducing the effects of spatially colored noise in evoked response magneto- and electro-encephalography data. The repeated component of the data, or signal of interest, is modeled as the mean, while the noise is modeled as the Kronecker product of a spatial and a temporal covariance matrix. The temporal covariance matrix is assumed known or estimated prior to the application of the algorithm. The spatial covariance structure is estimated as part of the maximum-likelihood procedure. The mean matrix representing the signal of interest is assumed to be low-rank due to the temporal and spatial structure of the data. The maximum-likelihood estimates of the components of the low-rank signal structure are derived in order to estimate the signal component. The relationship between this approach and principal component analysis (PCA) is explored. In contrast to prestimulus-based whitening followed by PCA, the maximum-likelihood approach does not require signal-free data for noise whitening. Consequently, the maximum-likelihood approach is much more effective with nonstationary noise and produces better quality whitening for a given data record length. The efficacy of this approach is demonstrated using simulated and real MEG data.
authors.affiliation: Department of Medical Physics, University of Wisconsin-Madison, Madison, WI 53706, USA. boris@cs.wisc.edu
authors.forename: Boris V
authors.initials: BV
authors.lastname: Baryshnikov
authors.forename: Barry D
authors.initials: BD
authors.lastname: Van Veen
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Wakai
mesh_terms: D000465:Algorithms; D001921:Brain / Q000502:physiology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004569:Electroencephalography / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D016013:Likelihood Functions; D015225:Magnetoencephalography / Q000379:methods*