a, Example GCaMP6f expression (green) and tyrosine hydroxylase (TH) antibody staining (red). Square indicates location of high-magnification view of GCaMP expression in TH+ neurons. Scale bars, 500 µm (top) and 100 µm (bottom). b, Quantification of penetrance and specificity of the Ai148×DAT::cre mouse line. Penetrance is the number of TH+ neurons also expressing GCaMP (mean: 95.2%; s.e.m.: 1.52%; n = 11 sections; 1,082 cells, 2 mice). Specificity is the number of GCaMP+ neurons that are also TH+ (mean: 96.7%; s.e.m.: 0.74%; n = 11 sections; 1,075 cells, 2 mice). c, Examples of lesions caused by GRIN lens implants (left). Insets are higher-magnification images of the regions in which TH+ neurons were counted underneath the lens and compared to counts contralateral to the lens. Scale bars, 50 µm. White overlay indicates location of the lesion. Cells were counted in 50 µm by 50 µm squares from 0–300 µm below the lens. d, Average number of TH+ neurons per 50 µm2 by distance from the bottom of the lens. Orange denotes average count under the lens; grey denotes average count from the contralateral hemisphere. Shading denotes s.e.m. n = 11 mice.