Ultra-compact fiber-optic two-photon microscope for functional fluorescence imaging in vivo.
We present a small, lightweight two-photon fiberscope and demonstrate its suitability for functional imaging in the intact brain. Our device consists of a hollow-core photonic crystal fiber for efficient delivery of near-IR femtosecond laser pulses, a spiral fiber-scanner for resonant beam steering, and a gradient-index lens system for fluorescence excitation, dichroic beam splitting, and signal collection. Fluorescence light is remotely detected using a standard photomultiplier tube. All optical components have 1 mm dimensions and the microscope's headpiece weighs only 0.6 grams. The instrument achieves micrometer resolution at frame rates of typically 25 Hz with a field-of-view of up to 200 microns. We demonstrate functional imaging of calcium signals in Purkinje cell dendrites in the cerebellum of anesthetized rats. The microscope will be easily portable by a rat or mouse and thus should enable functional imaging in freely behaving animals.
Engelbrecht
Christoph J
CJ
Dept. of Neurophysiology, Brain Research Institute, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Johnston
Richard S
RS
Seibel
Eric J
EJ
Helmchen
Fritjof
F
D000818:Animals; D002531:Cerebellum / Q000648:ultrastructure*; D003712:Dendrites / Q000648:ultrastructure*; D005336:Fiber Optic Technology / Q000295:instrumentation*; D007089:Image Enhancement / Q000295:instrumentation* / Q000379:methods; D051379:Mice; D036641:Microscopy, Fluorescence, Multiphoton / Q000295:instrumentation* / Q000379:methods; D008904:Miniaturization; D055100:Optical Fibers; D051381:Rats