Chronic imaging of movement-related Purkinje cell calcium activity in awake behaving mice

Abstract

Gaffield MA, Amat SB, Bito H, Christie JM. Chronic imaging of movement-related Purkinje cell calcium activity in awake behaving mice.

Conversion of graded presynaptic climbing fiber activity into graded postsynaptic Ca2+ signals by Purkinje cell dendrites

“…CF responses in Crus I were not due to motor action as sensory-related activity persisted under anesthesia-induced paralysis. In previous studies, we also observed lobule-specific differences in the representation of behavioral variables, with orofacial movements in response to reward consumption engaging neurons in Crus II but not Crus I (Gaffield et al, 2016;Gaffield and Christie, 2017). Combined, these results suggest partitioned representations of unpredicted sensations and mechanics of action within the lateral posterior hemispheres, cerebellar regions increasingly implicated in cognitive function in both humans and mice (Deverett et al, 2018;Schmahmann, 2018;Stoodley et al, 2017).…”

“…Time-series images of Ca 2+ activity in neurons expressing genetically encoded Ca 2+ indicators were aligned using a least-squares algorithm. PCs and CFs were segmented using an independent component analysis algorithm to group like-responding pixels (Hyvarinen, 1999) and Ca 2+ events identified using an inference-based method (Gaffield et al, 2016;Vogelstein et al, 2010). Ca 2+ event rates were calculated from each image (34 ms in duration).…”

“…Interestingly, there was evidence of partitioned processing of sensation and action within distinct regions of the lateral cerebellum. In lobule Crus II, where PCs are responsive to motorrelated CF activity (Gaffield et al, 2016;Gaffield and Christie, 2017), sensory cues failed to alter the rate of dendritic Ca 2+ events compared to baseline (1.22 ± 0.12 and 1.20 ± 0.14 Hz; prior to and during sensory stimuli, respectively; n = 39 trial blocks, 6 mice; p = 0.93; paired Student's t-test; Figure 1C). Given that sensory-triggered Ca 2+ events persisted in PCs of Crus I while animals were under anesthesia-induced paralysis, we rule out movement as the direct cause of CF responses in this region (Figure 1F).…”

“…2pLSM was used for measuring in vivo Ca 2+ activity in neurons of the lateral cerebellum with a custom-built, movable-objective microscope as described previously (Gaffield et al, 2016;Gaffield and Christie, 2017). Video-rate frame scanning (~30 frames/s) at high resolution (512 x 512 pixels) was achieved using an 8 kHz resonant scan mirror in combination with a galvanometer mirror (Cambridge Technologies; Bedford, MA).…”

Intact skull chronic windows for mesoscopic wide-field imaging in awake mice

“…Two approaches for delivering light to the brain are to either implant a light fiber, or to create a cranial window that provides optical access to the underlying cortex. The fiber-based approach can target subcortical structures that are not accessible via cranial windows (Aravanis et al, 2007;Gaffield et al, 2015), and can sample a field of view as large as 2 mm with the use of head-mounted microendoscopes (Jennings et al, 2015). However, mesoscopic mapping of cortical function-a spatial scale where the relationship among several functional regions can be examined (Oh et al, 2014;Silasi and Murphy, 2014) -requires optical access to an even larger area, with preferably non-invasive preparations to resolve map-like activity.…”