Light Scattering Properties Vary across Different Regions of the Adult Mouse Brain
2A: Measurements using the fiber punch-through technique were taken in seven different brain areas with blue (453 nm) light. In each case, optical transmittance decreased exponentially with tissue thickness; however, the exponential decreases observed varied greatly with the type of tissue. Single measurements are represented by the respective symbols while the solid lines represent exponential fits of the data. 2B: Effective attenuation coefficients with SEMs for the seven brain areas: VNTB 19.96+/−0.26; MNTB 18.16+/−0.69; LSO 17.92+/−0.80; PPT 15.26+/−0.78; OB 14.88+/−0.74; SC 13.91+/−0.83; Cerebellum 9.76+/−0.78; all units are 1/mm. 2C: Optical power values that would need to be fed into a 100 µm diameter optical fiber when 300 µm of tissue needs to be illuminated at intensities typically used for Channelrhodopsin activation. 2D: Same as figure C except that in this example the illumination was calculated to hypothetically activate Channelrhodopsin over a distance of 600 µm from the fiber tip.