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Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals
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Demanuele, Charmaine, James, C. J. and Sonuga-Barke, Edmund JS (2007) Distinguishing low frequency oscillations within the 1/f spectral behaviour of electromagnetic brain signals. Behavioral and Brain Functions, Vol. 3 (No. 1). p. 62. doi:10.1186/1744-9081-3-62 ISSN 1744-9081.
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Official URL: http://dx.doi.org/10.1186/1744-9081-3-62
Abstract
Background
It has been acknowledged that the frequency spectrum of measured electromagnetic (EM) brain signals shows a decrease in power with increasing frequency. This spectral behaviour may lead to difficulty in distinguishing event-related peaks from ongoing brain activity in the electro- and magnetoencephalographic (EEG and MEG) signal spectra. This can become an issue especially in the analysis of low frequency oscillations (LFOs) – below 0.5 Hz – which are currently being observed in signal recordings linked with specific pathologies such as epileptic seizures or attention deficit hyperactivity disorder (ADHD), in sleep studies, etc.
Methods
In this work we propose a simple method that can be used to compensate for this 1/f trend hence achieving spectral normalisation. This method involves filtering the raw measured EM signal through a differentiator prior to further data analysis.
Results
Applying the proposed method to various exemplary datasets including very low frequency EEG recordings, epileptic seizure recordings, MEG data and Evoked Response data showed that this compensating procedure provides a flat spectral base onto which event related peaks can be clearly observed.
Conclusion
Findings suggest that the proposed filter is a useful tool for the analysis of physiological data especially in revealing very low frequency peaks which may otherwise be obscured by the 1/f spectral activity inherent in EEG/MEG recordings.
Item Type: | Journal Article | ||||
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Divisions: | Faculty of Science, Engineering and Medicine > Engineering > WMG (Formerly the Warwick Manufacturing Group) | ||||
Journal or Publication Title: | Behavioral and Brain Functions | ||||
Publisher: | Bio Med Central | ||||
ISSN: | 1744-9081 | ||||
Official Date: | 2007 | ||||
Dates: |
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Volume: | Vol. 3 | ||||
Number: | No. 1 | ||||
Page Range: | p. 62 | ||||
DOI: | 10.1186/1744-9081-3-62 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Open Access (Creative Commons) |
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