All-fiber-transmission photometry for simultaneous optogenetic stimulation and multi-color neuronal activity recording

Abstract

Manipulating and real-time monitoring of neuronal activities with cell-type specificity and precise spatiotemporal resolution during animal behavior are fundamental technologies for exploring the functional connectivity, information transmission, and physiological functions of neural circuits in vivo. However, current techniques for optogenetic stimulation and neuronal activity recording mostly operate independently. Here, we report an all-fiber-transmission photometry system for simultaneous optogenetic manipulation and multi-color recording of neuronal activities and the neurotransmitter release in a freely moving animal. We have designed and manufactured a wavelength-independent multi-branch fiber bundle to enable simultaneous optogenetic manipulation and multi-color recording at different wavelengths. Further, we combine a laser of narrow linewidth with the lock-in amplification method to suppress the optogenetic stimulation-induced artifacts and channel crosstalk. We show that the collection efficiency of our system outperforms a traditional epi-fluorescence system. Further, we demonstrate successful recording of dynamic dopamine (DA) responses to unexpected rewards in the nucleus accumbens (NAc) in a freely moving mouse. We also show simultaneous dual-color recording of neuronal Ca 2+ signals and DA dynamics in the NAc upon delivering an unexpected reward and the simultaneous optogenetic activating at dopaminergic terminals in the same location. Thus, our multi-function fiber photometry system provides a compatible, efficient, and flexible solution for neuroscientists to study neural circuits and neurological diseases.

Lights, fiber, action! A primer on in vivo fiber photometry

“…For experiments that combine photometry with optogenetics, in addition to the spectral channels for acquiring signals, the system must be configured to allow light for optogenetic stimulation to be delivered through the same fiber. A suitable system may be purchased pre-configured or custom-built using published methods papers (e.g., Sych et al, 92 Qi et al, 93 and Formozov et al 94 ). Photometry systems compatible with simultaneous electrophysiology recordings are also commercially available or can be custom built (e.g., Patel et al 95 ).…”

Novel all-fiber-optic technology for control and multi-color probing of neural circuits in freely-moving animals

“…Advances have been made in optogenetics technology to avoid the spectral overlap between optogenetic stimulation light and excitation/emission light from genetically encoded calcium sensing fluorescein proteins (such as GCaMP) and other cell-typing/labelling proteins (such as RFP or YFP) 7,8 , thus avoiding or minimizing unwanted artifacts in neural activity signals or in optogenetic stimulation. Both optogenetic stimulation and multi-color cell-type-specific neural activity imaging can be realized in a bench-top microscopy system by using properly chosen optical filters/dichroic mirrors, but not in the currently available fiber photometry systems -which only cover the spectrum of light between 405-600 nm 8 . This precludes the possibility of optogenetic stimulation and multi-color neural activity imaging in freely behaving animals.…”