# The Complex-Pole Filter Representation (COFRE) for spectral modeling of fNIRS signals

arXiv: https://arxiv.org/abs/2105.13476 · HTML: https://mlsanity.com/paper/2105.13476/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 13 May 2021.

## Built on by (most cited first, 1 of 1)

- [ALPHABET: A Laplace-Pole History Aggregator with Banked Exponential Transport](https://mlsanity.com/paper/2608.24051/) (2026)

## Abstract (arXiv)

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.