TY - JOUR T1 - Realistic numerical and analytical modeling of light scattering in brain tissue for optogenetic applications JF - eneuro JO - eneuro DO - 10.1523/ENEURO.0059-15.2015 SP - ENEURO.0059-15.2015 AU - Guy Yona AU - Nizan Meitav AU - Itamar Kahn AU - Shy Shoham Y1 - 2016/01/04 UR - http://www.eneuro.org/content/early/2016/01/04/ENEURO.0059-15.2015.abstract N2 - Optogenetics has in recent years become a central tool in neuroscience research. Estimating the transmission of visible light through brain tissue is of crucial importance for controlling the activation levels of neurons in different depths, designing the optical systems and avoiding lesions from excessive power density. The Kubelka-Munk model and Monte Carlo simulations have previously been used to model light propagation through rodents' brain tissue, however, these prior attempts suffer from fundamental shortcomings. Here, we introduce and study two modified approaches for modeling the distributions of light emanating from a multimode fiber and scattering through tissue, using both realistic numerical Monte Carlo simulations and an analytical approach based on the Beam Spread Function approach. We demonstrate a good agreement of the new methods' predictions both with recently published data, and with new measurements in mouse brain cortical slices, where our results yield a new cortical scattering length estimate of ∼47 µm at λ = 473 nm, significantly shorter than ordinarily assumed in optogenetic applications.Significance statement For optogenetic stimulation to become highly controlled, reproducible and safe, a thorough understanding of the deep-tissue scattered light distributions that mediate the excitation is required. However, effective computation tools validated by actual measurements in brain tissue are currently still lacking. In this paper, we introduce, study and validate new numerical and analytical approaches for modeling the distributions of light propagating through brain tissue. We show that both methods lead to consistent results and use the much faster analytical method to iteratively extract the optical parameters from new measurements, suggesting that light penetration into cortical tissue is significantly less than usually assumed. The new level of faithfulness could assist in designing experimental setups and optical interfaces, and help interpret optogenetics experiments. ER -