Fig. 28.

2P and 3P wearable microscopes for cellular-resolution imaging in freely behaving animals. (a) Example 2P miniscope for high-resolution imaging at depth. This implementation weighs 4.2 grams and includes an electrically tunable lens (ETL) (top right) for rapid focus adjustment across a $180\mu \mathrm{m}$ focal range (bottom right). Using a microelectromechanical system (MEMS) scanner, the miniscope allows 10 Hz recordings at 512 x 512 pixels resolution across a $420\mu \mathrm{m}$ FOV. (b) Example images of GCaMP6s-expressing neurons acquired at the indicated focal depths (z) in the mouse prefrontal cortex. (c) ${\mathrm{Ca}}^{2+}$ transients from dendritic (top) and cell body regions of interest (ROIs) (bottom) within the focal planes shown in (b). (d) 3P miniscope for deep, high-resolution imaging. This microscope weighs 5 grams and includes a 1.2-m hollow-core photonic bandgap crystal fiber (HC-PBGF) (right) for low-dispersion delivery of the $\sim 1,320\mathrm{nm}$ excitation light-pulses. A plastic optical fiber collects the emitted fluorescence for remote detection by photomultiplier tubes (PMTs). (e) Image of GCaMP6s-labeled rat cortical neurons at the indicated focal depth (z) in the posterior parietal cortex. (f) ${\mathrm{Ca}}^{2+}$ spiking from four example neurons recorded at $1,120\mu \mathrm{m}$ cortical depth. (a)–(f) Adapted with permission from Nature Publishing Group: (a)–(c) from Ref. 418 and (d)–(f) from Ref. 417.