Optimizing Thermal Block Length During Infrared Neural Inhibition to Minimize Temperature Thresholds
Document Type
Article
Publication Date
10-1-2021
Abstract
Objective. Infrared neural inhibition (INI) is a method of blocking the generation or propagation of neural action potentials through laser heating with wavelengths strongly absorbed by water. Recent work has identified that the distance heated along axons, the block length (BL), modulates the temperature needed for inhibition; however, this relationship has not been characterized. This study explores how BL during INI can be optimized towards minimizing its temperature threshold. Approach. To understand the relationship between BL and the temperature required for INI, excised nerves from Aplysia californica were laser-heated over different lengths of axon during electrical stimulation of compound action potentials. INI was provided by irradiation (λ = 1470 nm) from a custom probe (n = 6 nerves), and subsequent validation was performed by providing heat block using perfused hot media over nerves (n = 5 nerves). Main Results. Two BL regimes were identified. Short BLs (thermal full width at half maximum (tFWHM) = 0.81-1.13 mm) demonstrated that increasing the tFWHM resulted in lower temperature thresholds for INI (p < 0.0125), while longer BLs (tFWHM = 1.13-3.03 mm) showed no significant change between the temperature threshold and tFWHM (p > 0.0125). Validation of this longer regime was performed using perfused hot media over different lengths of nerves. This secondary heating method similarly showed no significant change (p > 0.025) in the temperature threshold (tFWHM = 1.25-4.42 mm). Significance. This work characterized how the temperature threshold for neural heat block varies with BL and identified an optimal BL around tFWHM = 1.13 mm which minimizes both the maximum temperature applied to tissue and the volume of tissue heated during INI. Understanding how to optimally target lengths of nerve to minimize temperature during INI can help inform the design of devices for longitudinal animal studies and human implementation.
Keywords
block length, heat block, infrared neural inhibition, infrared neural stimulation, neuromodulation
Language
English
Publication Title
Journal of Neural Engineering
Grant
/ SPARC OT2 OD025307
Rights
© 2021 The Author(s). This is an Open Access work distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Ford JB, Ganguly M, Zhuo J, McPheeters MT, Jenkins MW, Chiel HJ, Jansen ED. Optimizing thermal block length during infrared neural inhibition to minimize temperature thresholds. J Neural Eng. 2021 Apr 8;18(5):10.1088/1741-2552/abf00d. doi: 10.1088/1741-2552/abf00d. PMID: 33735846; PMCID: PMC11189657.
Manuscript Version
Final Publisher Version