Focus-tunable microscope for imaging small neuronal processes in freely moving animals

Abstract

Miniature single-photon microscopes have been widely used to image neuronal assemblies in the brain of freely moving animals over the last decade. However, these systems have important limitations for imaging in-depth fine neuronal structures. We present a subcellular imaging single-photon device that uses an electrically tunable liquid crystal lens to enable a motion-free depth scan in the search of such structures. Our miniaturized microscope is compact ( 10 mm × 17 mm × 12 mm ) and lightweight ( ≈ 1.4 g ), with a fast acquisition rate (30–50 frames per second), high magnification ( 8.7 × ), and high resolution (1.4 μm) that allow imaging of calcium activity of fine neuronal processes in deep brain regions during a wide range of behavioral tasks of freely moving mice.

Miniaturized microscope for non-invasive imaging of leukocyte-endothelial interactions in human microcirculation

“…2g). To make the instrument even more compact, the current focusing mechanism (a translational stage) can be replaced with an electrically tunable lens 17 . In addition, the high-speed CMOS sensor (frame rate up to 1000 Hz) can be replaced by a standard (30 Hz) video camera that will still be able to image rolling and adherent cells, but the flowing cells will not be resolved at this frame rate.…”

Advances of optical miniscopes for in vivo imaging of neural activity in freely moving animals

“…However, for portability, smaller and lighter components need to be selected. As shown in Figure 2 , typical structures of a head-mounted, single-photon fluorescence miniscope ( Ghosh et al, 2011 ; Scott et al, 2018 ; Barbera et al, 2019 ; Bagramyan et al, 2021 ; Rynes et al, 2021 ) include light source, filters, dichroic mirror (to separate excitation light from emitted fluorescence), objective lens, imaging sensor (such as CMOS camera), etc. In single-photon miniscopes, a high-brightness LED and a CMOS camera are usually integrated on the head-wearing part of the miniscopes for wide-field illumination and signal recording, respectively.…”

“…For power supply and data transmission, the single-photon fluorescence miniscopes are generally wired with electric and data cables ( Ghosh et al, 2011 ; Scott et al, 2018 ; Bagramyan et al, 2021 ; Rynes et al, 2021 ). However, the cable, which connects the miniscope and the data acquisition module, increases the weight of the wearing parts, and the torque generated also interferes the animal activity.…”

A Systematically Optimized Miniaturized Mesoscope (SOMM) for large-scale calcium imaging in freely moving mice

“…Moreover, due to a typically low depth of field (DOF) [10], these image-forming systems are also vulnerable to motion-induced artifacts arising from axial focus drift [20] during free behavior. While components such as electro-tunable lenses and other devices [21] allow for quick adjustment of focus and working distance without mechanical repositioning [16], active compensation for motion-induced axial focus drift during population recordings remains challenging. Thus, to date, these and other technical difficulties have prevented the realization of image-forming devices that offer multi-millimeter FOV, cellular resolution, tolerable weight, and robustness against axial drift in freely behaving rodents.…”