Validation of the flash-evoked response from fetal MEG.
Flash-evoked responses can be recorded from the fetus in utero. However, a standard analysis approach based on orthogonal projection (OP) to attenuate maternal and fetal cardiac signals leads to a spatial redistribution of the signal. This effect prevents the correlation of source location with a known fetal head location in some cases and the signal-to-noise ratio (SNR) is sometimes limited such that the response latency is difficult to determine. We used a modified beamformer model search analysis to avoid the redistribution shortcoming and to improve the SNR. We included a statistical test for residual interference in the average and quantified significance of the evoked response with a bootstrap method. Selected source locations compared favorably to fetal head locations estimated from ultrasound exams. The evoked response time course was found to have a significant post-trigger peak with a latency between about 180 and 770 ms in more than 90% of the subject measurements. These results confirm that the combined application of a beamformer model search and bootstrap significance test provides a validation of the flash-evoked response observed in OP processed fetal MEG channels.
McCubbin
J
J
Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
Murphy
P
P
Eswaran
H
H
Preissl
H
H
Yee
T
T
Robinson
S E
SE
Vrba
J
J
D000465:Algorithms; D001921:Brain / Q000196:embryology* / Q000502:physiology*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005323:Fetal Monitoring / Q000379:methods*; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods*; D010775:Photic Stimulation / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity