Fluorescence dual-color fiberscope for monitoring neuron and astrocyte concurrent activities in freely-behaving animals

Multicore fiber optic imaging reveals that astrocyte calcium activity in the mouse cerebral cortex is modulated by internal motivational state

“…Here, we used an objective lens assembled from two pairs of aspheric miniature lenses to collect and focus emitted light onto the end of a 30,000-core fiber bundle to enable cellular resolution of active regions 40,42 . Importantly, by using lenses with an extended focal length, this removable, lightweight, small form factor device enabled longitudinal imaging through an implanted cranial window with minimal behavioral interruption 45 , providing sufficient spatiotemporal resolution and sensitivity to resolve cellular fluorescence changes within the intact brain while animals were engaged in normative behaviors. Although this system operates in an epifluorescence mode, each optical fiber core intrinsically acts as a spatial filter to prevent photons from outside the focal plane to infiltrate, providing better optical sectioning than a traditional wide-field epifluorescence microscope 33,74 .…”

“…The ability to modify imaging parameters, such as light sources, filters, and optic sensors remotely using standard tabletop optical components in this system affords rapid and extensive adaptation to experimental needs. Further modifications to this system could be implemented to enable deeper structure observation and high resolution with multi-photon excitation and/or adaptive optics; fast three-dimensional imaging using adaptive lenses and laser scanning; multicolor detection and laser speckle contrast imaging to resolve interactions between cell types and blood flow; and holographic or random-access fiber illumination to manipulate cellular activity patterns using optogenetics 33,45,75,76 .…”

“…To allow imaging of cortical astrocyte activity in freely moving mice, we used a rigid, adjustable metal collet to secure the lensed-fiberscope to the mouse skull (Fig. 2a) 45 . This mount allowed fine positioning of the fiber relative to the cranial window in both x-y and z planes, and facilitated longitudinal analysis of astrocyte activity over multiple days, as the fiberscope could be removed and readily repositioned to image the same focal plane, using the surface blood vessels as fiducial landmarks (Supplementary Fig.…”

Multicore fiber optic imaging reveals that astrocyte calcium activity in the cerebral cortex is modulated by internal motivational state

“…The ability to modify imaging parameters, such as light sources, filters, and optic sensors remotely using standard tabletop optical components in this system affords rapid and extensive adaptation to experimental needs. Further modifications to this system could be implemented to enable deeper structure observation and high resolution with multi-photon excitation and/or adaptive optics; fast three-dimensional imaging using adaptive lenses and laser scanning; multicolor detection and laser speckle contrast imaging to resolve interactions between cell types and blood flow; and holographic or random-access fiber illumination to manipulate cellular activity patterns using optogenetics (Accanto et al, 2022;Cha et al, 2015;Pak et al, 2021;Plöschner et al, 2015;Soleimanzad et al, 2019). Although requiring fewer miniature elements than headmounted miniscopes, this system requires assembly of the multi-lens array and fiber optic coupling.…”

“…To enable visualization of astrocyte calcium changes within the cerebral cortex of freely moving animals, we developed a widefield, long working distance fiber optic imaging system capable of resolving cellular changes in fluorescence emitted by genetically encoded calcium indicators in vivo. Taking advantage of spatial-division multiplexing optics, this approach uses a multi-core optical fiber coupled to miniature lenses that provide sufficient working distance to be mounted outside of a cranial window, minimizing brain injury (Cha and Kang, 2014;Cha et al, 2015;Pak et al, 2021). This platform enables repetitive imaging over long periods to delineate the activity patterns of both individual astrocytes and multicellular astrocyte networks in the upper layers of the cerebral cortex, which receives extensive neuromodulatory input.…”