The Importance of Properly Compensating for Head Movements During MEG Acquisition Across Different Age Groups
- 206 Downloads
Unlike EEG sensors, which are attached to the head, MEG sensors are located outside the head surface on a fixed external device. Subject head movements during acquisition thus distort the magnetic field distributions measured by the sensors. Previous studies have looked at the effect of head movements, but no study has comprehensively looked at the effect of head movements across age groups, particularly in infants. Using MEG recordings from subjects ranging in age from 3 months through adults, here we first quantify the variability in head position as a function of age group. We then combine these measured head movements with brain activity simulations to determine how head movements bias source localization from sensor magnetic fields measured during movement. We find that large amounts of head movement, especially common in infant age groups, can result in large localization errors. We then show that proper application of head movement compensation techniques can restore localization accuracy to pre-movement levels. We also find that proper noise covariance estimation (e.g., during the baseline period) is important to minimize localization bias following head movement compensation. Our findings suggest that head position measurement during acquisition and compensation during analysis is recommended for researchers working with subject populations or age groups that could have substantial head movements. This is especially important in infant MEG studies.
KeywordsMagnetoencephalography Head movement Movement compensation Signal space separation Artifact correction Brain development
Funding for this work was provided in part by a grant from the Washington State Life Sciences Discovery Fund (LSDF).
- Chen Y, Medioni G (1991) Object modeling by registration of multiple range images. In: 1991 IEEE international conference on robotics and automation, 1991. Proceedings, vol 3., pp 2724–9. doi: 10.1109/ROBOT.1991.132043
- Knappe S, Tilmann S, Trahms L (2014) Optically-pumped magnetometers for MEG. In: Supek S, Aine CJ (eds) Magnetoencephalography. Springer, Berlin, pp 993–999Google Scholar
- Medvedovsky M, Taulu S, Bikmullina R, Paetau R (2007) Artifact and head movement compensation in MEG. Neurol Neurophysiol Neurosci 4:1–10Google Scholar
- Nenonen J, Nurminen J, Kičić D, Bikmullina R, Lioumis P, Jousmäki V, Taulu S, Parkkonen L, Putaala M, Kähkönen S (2012) Validation of head movement correction and spatiotemporal signal space separation in magnetoencephalography. Clin Neurophysiol 123(11):2180–2191. doi: 10.1016/j.clinph.2012.03.080 CrossRefPubMedGoogle Scholar
- Taulu S, Kajola M (2005) Presentation of electromagnetic multichannel data: the signal space separation method. J Appl Phys 97(12):124905–5–10. doi: 10.1063/1.1935742
- World Health Organization (2016) Head circumference-for-age (BOYS). http://www.who.int/childgrowth/standards/second_set/cht_hcfa_boys_p_0_5.pdf?ua=1