No abstract

Understanding how neural circuits process information requires rapid measurements of activity from identified neurons distributed in 3D space. Here we describe an acousto-optic lens two-photon microscope that performs high-speed focusing and line scanning within a volume spanning hundreds of micrometers. We demonstrate its random-access functionality by selectively imaging cerebellar interneurons sparsely distributed in 3D space and by simultaneously recording from the soma, proximal and distal dendrites of neocortical pyramidal cells in awake behaving mice.

Two-photon microscopy is widely used to investigate brain function across multiple spatial scales. However, measurements of neural activity are compromised by brain movement in behaving animals. Brain motion-induced artefacts are typically corrected using post-hoc processing of 2D images, but this approach is slow and does not correct for axial movements. Moreover, the deleterious effects of brain movement on high speed imaging of small regions of interest and photostimulation cannot be corrected post-hoc . To address this problem, we combined random access 3D laser scanning using an acousto-optic lens and rapid closed-loop FPGA processing to track 3D brain movement and correct motion artifacts in real-time at up to 1 kHz. Our recordings from synapses, dendrites and large neuronal populations in behaving mice and zebrafish demonstrate real-time movement corrected 3D two-photon imaging with sub-micrometer precision.

Pulp tissue and predentine removal were not significantly different between a step-back filing and an automated rotary preparation technique in conjunction with water or NaOCl.