Focus-tunable microscope for imaging small neuronal processes in freely moving animals
Arutyun Bagramyan, Loïc Tabourin, Ali Rastqar, Narges Karimi, Frédéric Bretzner, Tigran Galstian
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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:mn>10</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>17</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>12</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>mm</mml:mi> </mml:mrow> </mml:math> ) and lightweight ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:mo form="prefix">≈</mml:mo> <mml:mn>1.4</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">g</mml:mi> </mml:mrow> </mml:math> ), with a fast acquisition rate (30–50 frames per second), high magnification ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m3"> <mml:mrow> <mml:mn>8.7</mml:mn> <mml:mo form="postfix">×</mml:mo> </mml:mrow> </mml:math> ), 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.