Fetal MEG evoked response latency from beamformer with random field theory

J. McCubbin, J. Vrba, P. Murphy, J. Temple, H. Eswaran, C.L. Lowery, H. Preissl
2010 NeuroImage  
Analysis of fetal magnetoencephalographic brain recordings is restricted by low signal to noise ratio (SNR) and non-stationarity of the sources. Beamformer techniques have been applied to improve SNR of fetal evoked responses. However, until now the effect of non-stationarity was not taken into account in detail, because the detection of evoked responses is in most cases determined by averaging a large number of trials. We applied a windowing technique to improve the stationarity of the data by
more » ... using short time segments recorded during a flash evoked study. In addition, we implemented a random field theory approach for more stringent control of false positives in the statistical parametric map of the search volume for the beamformer. The search volume was based on detailed individual fetal/maternal biometrics from ultrasound scans and fetal heart localization. Average power over a sliding window within the averaged evoked response against a randomized average background power was used as the test z -statistic. The significance threshold was set at 10% over all members of a contiguous cluster of voxels. There was at least one significant response for 62% of fetal and 95% of newborn recordings with gestational age (GA) between 28 and 45 weeks from 29 subjects. We found that the latency was either substantially unchanged or decreased with increasing GA for most subjects, with a nominal rate of about −11 ms/week. These findings support the anticipated neurophysiological development, provide validation for the beamformer model search as a methodology, and may lead to a clinical test for fetal cognitive development. Keywords fetal magnetoencephalography; evoked response latency; statistical significance; beamformer; MEG; random field theory Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
doi:10.1016/j.neuroimage.2009.08.019 pmid:19686855 pmcid:PMC2764827 fatcat:6g5n7fklhbebrphvt4gzuz3b34