A flexible and versatile system for multicolor fiber photometry and optogenetic manipulation

Fiber photometry is a technique of growing popularity in neuroscientific research. It is widely used to infer brain activity by recording calcium dynamics in genetically defined populations of neurons. Aside from the wide variety of calcium indicators, other genetically encoded biosensors have recently been engineered to measure membrane potential, neurotransmitter release, pH, or various cellular metabolites, such as ATP or cAMP. Due to the spectral characteristics of these molecular tools, different assemblies of optical hardware are usually needed to reveal the full potential of different biosensors. In addition, the combination of multiple biosensors in one experiment often requires the investment in more complex equipment, which limits the flexibility of the experimental design. Such constraints often hamper a straightforward implementation of new molecular tools, evaluation of their performance in vivo, and design of new experimental paradigms - especially if the financial budget is a limiting factor. Here, we propose a novel approach for fiber photometry recordings, based on a multimode optical fused-fiber coupler (FFC) for both light delivery and collection. Recordings can readily be combined with optogenetic manipulations in a single device without the requirement for dichroic beam-splitters. In combination with a multi-color light source and appropriate emission filters, our approach offers remarkable flexibility in experimental design and facilitates the implication of new molecular tools in vivo at minimal cost. The ease of assembly, operation, characterization, and customization of this platform holds the potential to foster the development of experimental strategies for multicolor fused fiber photometry (FFP) combined with optogenetics far beyond its current state. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=186 SRC="FIGDIR/small/484590v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@13abbdcorg.highwire.dtl.DTLVardef@10384d7org.highwire.dtl.DTLVardef@67938org.highwire.dtl.DTLVardef@1005aee_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIFused Fiber Photometry (FFP) enables straightforward monitoring and manipulation of brain activity C_LIO_LIFFP allows monitoring of indicators with virtually any spectral characteristics C_LIO_LIFFP is compatible with simultaneous optogenetic manipulation C_LIO_LIEasy assembly, characterization, and customization C_LI