Characterization of fiber-optic light delivery and light-induced temperature changes in a rodent brain for precise optogenetic neuromodulation

Younghoon Shin; Minsu Yoo; Hyung-Sun Kim; Sung-Ki Nam; Hyoung-Ihl Kim; Sun-Kyu Lee; Sohee Kim; Hyuk-Sang Kwon

doi:10.1364/BOE.7.004450

Characterization of fiber-optic light delivery and light-induced temperature changes in a rodent brain for precise optogenetic neuromodulation

Biomed Opt Express. 2016 Oct 6;7(11):4450-4471. doi: 10.1364/BOE.7.004450. eCollection 2016 Nov 1.

Authors

Younghoon Shin¹, Minsu Yoo², Hyung-Sun Kim³, Sung-Ki Nam⁴, Hyoung-Ihl Kim¹, Sun-Kyu Lee⁴, Sohee Kim⁵, Hyuk-Sang Kwon⁶

Affiliations

¹ Department of Biomedical Science and Engineering, and Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-Gwagiro, Buk-Gu, Gwangju 61005, South Korea.
² Graduate Program in Computational Neuroscience, University of Chicago, Chicago, Illinois 60637, USA.
³ Korea Institute of Toxicology (KIT), 141 Gajeong-Ro, Yuseong-Gu, Daejon 34114, South Korea.
⁴ Department of Mechanical Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-Gwagiro, Buk-Gu, Gwangju 61005, South Korea.
⁵ Department of Robotics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, South Korea.
⁶ Department of Biomedical Science and Engineering, and Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-Gwagiro, Buk-Gu, Gwangju 61005, South Korea; Department of Mechanical Engineering, Gwangju Institute of Science and Technology (GIST), 123 Cheomdan-Gwagiro, Buk-Gu, Gwangju 61005, South Korea.

Abstract

Understanding light intensity and temperature increase is of considerable importance in designing or performing in vivo optogenetic experiments. Our study describes the optimal light power at target depth in the rodent brain that would maximize activation of light-gated ion channels while minimizing temperature increase. Monte Carlo (MC) simulations of light delivery were used to provide a guideline for suitable light power at a target depth. In addition, MC simulations with the Pennes bio-heat model using data obtained from measurements with a temperature-measuring cannula having 12.3 mV/°C of thermoelectric sensitivity enabled us to predict tissue heating of 0.116 °C/mW on average at target depth of 563 μm and specifically, a maximum mean plateau temperature increase of 0.25 °C/mW at 100 μm depth for 473 nm light. Our study will help to improve the design and performance of optogenetic experiments while avoiding potential over- and under-illumination.

Keywords: (170.3660) Light propagation in tissues; (170.5280) Photon migration; (170.7050) Turbid media; (350.5340) Photothermal effects.