Fig. 3

TIS window for three-photon microscopy. a, b Representative images of the three-photon microscopy of neurons in a Thy1-YFP mouse at the 1300-nm excitation wavelength and at various depths before a and after b the TIS window establishment. c Signal intensity along the dashed lines in (a, b). d A 3D reconstruction image before and after the TIS window establishment. It was only achievable above 400 μm through an intact skull. e SBR at each depth before and after the TIS window establishment. The images were obtained using a 20 × objective; the excitation wavelength was 1300 nm (400 kHz, 50 fs); the axial step was set at 5 μm. Identical results were obtained in 3 mice