publications

Review of Cochlear Mechanics Results from OCT (Olson, Dong et al., 2024)

This is a multi-author paper regarding advances in cochlear mechanics made through optical coherence tomography. The range of the results is broad, and shows the expansive applications of this technology. My section, 2.5, is titled "Two issues arising from the uni-directional optical axis, and how to account for them." It is, in essence, a summary of my previous work (Frost et al., 2022, 2023) regarding the limitations of OCT as a 1-D vibrometer. I am proud that these results have been appreciated sufficiently to warrant my being an author on this work!

Read it here! Or download as a PDF.

Regional differences in cochlear nonlinearity (Strimbu et al., 2024)

This work was originally titled "A frame and a hotspot in cochlear mechanics" - an apt name, as we argue that the nonlinearity seen in the base of the gerbil cochlea comes in two distinct flavors depending on the position within the organ of Corti. The nonlinearity at the best frequency (BF) is present across the whole organ, but sub-BF nonlinearity is localized mostly to the region containing the outer hair cells and Deiters cells (the hotspot, where displacements are usually maximum). The rest of the organ surrounding this hotspot can be thought of as a frame. In the classic model of cochlear mechanics, it seems the outer hair cells "deliver nonlinearity" to the frame only near BF.

Citation: C. Elliott Strimbu, Lauren A. Chiriboga, Brian L. Frost, Elizabeth S. Olson; Regional differences in cochlear nonlinearity across the basal organ of Corti of gerbil, Hearing Research 12 January 2024; 443: 108951.
Read it here! Or download as a PDF.

Tutorial: The WKB approximation for models of cochlear mechanics (Frost, 2024)

This is a tutorial article for the Journal of the Acoustical Society of America, outlining Wentzel-Kramers-Brillouin methods for approximating solutions to 1-D and 2-D linear box models in cochlear mechanics. The tutorial covers mathematical theory and computational implementation. It is directed at younger scientists who may be unaware of the method (as well as its power and its weaknesses) despite its prolific appearance across cochlear mechanics modeling literature. It was also a blast to write, digging into the dense and rich past of cochlear mechanics modeling and mathematical physics!

Citation: Brian L. Frost; Foundations of the Wentzel-Kramers-Brillouin approximation for models of cochlear mechanics in 1- and 2-D. J. Acoust. Soc. Am. 1 January 2024; 155 (1): 358–379.
Read the tutorial - it's open access! Or download as a PDF.

Compressed sensing for OCT vibrometry (Frost et al., 2023)

This is a collaboration with Nikola Janjušević, PhD - a close friend from university and a postdoctoral associate at New York University Langone Health. We designed a classical algorithm based in total generalized variation optimization to reduce the number of samples required to acquire high-resolution displacement maps. The focus was on cochlear displacement responses measured using optical coherence tomography, but the method is sufficiently general to apply to any 2-D or 3-D map of displacement responses.

Citation: Frost, Brian & Janjušević, Nikola & Strimbu, C. & Hendon, Christine. (2023). Compressed sensing on displacement signals measured with optical coherence tomography. Biomedical Optics Express 14.
Read it here! Or download as a PDF.

High-efficiency model for axonal swelling (Frost and Mintchev, 2023)

Dr Mintchev and I began working on this project when I was an undergraduate at Cooper Union. We were interested in characterizing the network-level effects of axonal swelling, which has been studied on the single-axon level by Maia and Kutz. The axons may nonlinearly filter spike trains depending on the character of the damage. We simplified the complicated axon model (a system of PDEs) to a simple statistical algorithm, allowing network-scale simulation in a reasonable time frame. We found that in simple networks, presynaptic inhibition improves resilience to such damage.

Citation: Frost, B.L., Mintchev, S.M. A high-efficiency model indicating the role of inhibition in the resilience of neuronal networks to damage resulting from traumatic injury. J Comput Neurosci 51, 463–474 (2023).
Read it here! Or download as a PDF.

Reconstruction of 2-D vibrations in the cochlea using OCT (Frost et al., 2023)

This was a critical work in my doctoral thesis (under the advisement of Drs. Elizabeth Olson and Christine Hendon). We presented a method by which 2-D vibration maps in the organ of Corti could be reconstructed from 1-D optical coherence tomography measurements. The basic principal is to measure at different angles, and backproject multiple 1-D measurements from the same location to reconstruct 2-D and 3-D displacements. The clever bit is that we used physiology rather than image processing to register points between measurement angles.

Citation: Frost, Brian & Strimbu, Clark & Olson, Elizabeth. (2023). Reconstruction of transverse-longitudinal vibrations in the organ of Corti complex via optical coherence tomography. The Journal of the Acoustical Society of America 153.
Read it here! Or download as a PDF (erratum).

Determining anatomical coordinates for OCT measurements in the cochlea (Frost et al., 2022)

This was a critical work in my doctoral thesis (under the advisement of Drs. Elizabeth Olson and Christine Hendon). We presented a method by which one can relate the optical coordinates inherent to the OCT system ("the lab frame") to the anatomical coordinates of the cochlea (longitudinal, radial, transverse). Underlying this is a simple planar approximation of the basilar membrane. This may be the work I am the most proud of! It even made the cover of the JASA volume that it was in. I discussed a cross-section of this work in a Thorlabs Webinar, primarily given by Lisa Olson and Elliott Strimbu (my part starts at 43:25).

Citation: Brian L. Frost, Clark Elliott Strimbu, Elizabeth S. Olson; Using volumetric optical coherence tomography to achieve spatially resolved organ of Corti vibration measurements. J. Acoust. Soc. Am. 1 February 2022; 151 (2): 1115–1124.
Read it here! Or download as a PDF.

Model of the cochlea microphonic suggests sharper tuning at the hair bundles (Frost and Olson, 2021)

We solved a simple model of the cochlear microphonic using the finite element method and came to three main conclusions: 1) the size of the mechanoelectric transduction current is probably about 3 times larger in vivo than it is in vitro; 2) the differential radial motion at the hair bundle is tuned more sharply than the transverse motion at the basilar membrane; 3) certain features of microphonic responses are likely the result of a damaged cochlear base. The latter two of these predictions have been corroborated by data, so I'll call this one a success!

Citation: Frost B, Olson ES. Model of cochlear microphonic explores the tuning and magnitude of hair cell transduction current. Biophys J. 2021 Sep 7;120(17):3550-3565.
Read it here! Or download as a PDF.