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The Complex-Pole Filter Representation (COFRE) for Spectral Modeling of fNIRS Signals

Top: the response of a COFRE filter centered at a normalized frequency of 0.2, with its rise time marked. Bottom: rise time against filter bandwidth for four values of the filter parameter.
Rise time of the complex-pole filters as a function of their bandwidth.
Two panels of spectrum contrast for the HbR signal at channels T3 and T4, control group in red and tinnitus group in blue, across the endothelial, neurogenic, myogenic, respiratory and cardiac frequency bands.
Spectrum contrast of deoxygenated hemoglobin (HbR) at the left (T3) and right (T4) temporal channels, control against tinnitus.

arXiv:2105.13476

Authors: Pinto-Orellana, Marco A. and Mirtaheri, Peyman and Hammer, Hugo L.

Abstract

The complex-pole frequency representation (COFRE) is introduced in this paper as a new approach for spectrum modeling in biomedical signals. Our method allows us to estimate the spectral power density at precise frequencies using an array of narrow band-pass filters with single complex poles. Closed-form expressions for the frequency resolution and transient time response of the proposed filters have also been formulated. In addition, COFRE filters have a constant time and space complexity allowing their use in real-time environments. Our model was applied to identify frequency markers that characterize tinnitus in very-low-frequency oscillations within functional near-infrared spectroscopy (fNIRS) signals. We examined data from six patients with subjective tinnitus and seven healthy participants as a control group. A significant decrease in the spectrum power was observed in tinnitus patients in the left temporal lobe. In particular, we identified several tinnitus signatures in the spectral hemodynamic information, including (a.) a significant spectrum difference in one specific harmonic in the metabolic/endothelial frequency region, at 7mHz, for both chromophores and hemispheres; and (b.) a significant differences in the range 30-50mHz in the neurogenic/myogenic band.

BibTeX

@article{ComplexPoleFilterRepresentation-Pinto-Orellana-2021,
  title = {The {{Complex-Pole Filter Representation}} ({{COFRE}}) for Spectral Modeling of {{fNIRS}} Signals},
  author = {{Pinto-Orellana}, Marco A. and Mirtaheri, Peyman and Hammer, Hugo L.},
  year = {2021},
  journal = {arXiv:2105.13476 [physics, q-bio, stat]},
  eprint = {2105.13476},
  primaryclass = {physics, q-bio, stat},
  archiveprefix = {arXiv},
  keywords = {Physics - Medical Physics,Quantitative Biology - Quantitative Methods,Statistics - Methodology}
}