Large-volume and deep brain imaging in rabbits and monkeys using COMPACT two-photon microscopy

Abstract

In vivo imaging has been widely used for investigating the structure and function of neurons typically located within ~ 800 μm below the cortical surface. Due to light scattering and absorption, it has been difficult to perform in-vivo imaging of neurons in deep cortical and subcortical regions of large animals with two-photon microscopy. Here, we combined a thin-wall quartz capillary with a GRIN lens attached to a prism for large-volume structural and calcium imaging of neurons located 2 mm below the surface of rabbit and monkey brains. The field of view was greatly expanded by rotating and changing the depth of the imaging probe inside a quartz capillary. Calcium imaging of layer 5/6 neurons in the rabbit motor cortex revealed differential activity of these neurons between quiet wakefulness and slow wave sleep. The method described here provides an important tool for studying the structure and function of neurons located deep in the brains of large animals.

More than double the fun with two-photon excitation microscopy

“…The effective light throughput and resolution will be influenced by the properties of the GRIN lens such as numerical aperture or field curvature. Combination of this technology with AO 75 , improving the field of view 76 , imaging speed 77 and resolution 78 of GRIN lens systems and fiber based alternatives 79 are active and exciting areas of research. Often, imaging requires immobilization of the specimen, for example the mouse, which can be circumvented by head-mounted TPE microscopes allowing to image brain activity in freely moving animals [80][81][82] .…”