Mesoscopic Imaging: Shining a Wide Light on Large-Scale Neural Dynamics

Dual color mesoscopic imaging reveals spatiotemporally heterogeneous coordination of cholinergic and neocortical activity

“…This approach resulted in cortex-wide, uniform expression of both reporters (Figure S1), and we confirmed both ex vivo and in vivo that ACh3.0 specifically reported cholinergic signaling (Figure S2). We then performed mesoscopic imaging 10 of both reporters through the intact skull of mice that were head-fixed and freely running on a wheel (Figure 1a, see Methods). Imaging was performed by strobing 575nm (jRCaMP1b), 470nm (ACh3.0), and 395nm (control) excitation light with an overall frame rate of 10 Hz per channel.…”

“…A growing body of research suggests that arousal, measured using a variety of metrics including elevated motor activity, is associated with distinct alterations in local circuit operations within the neocortex, including changes in mean firing rates and decorrelation of the spike output of neighboring cells 3, 6-9 . Moreover, widefield, mesoscopic imaging 10 has revealed broad representation of motor signals across the cortex 8 , with changes in behavioral state also linked to reorganization of functionally connected cortical networks 11, 12 . While desynchronization of local cortical network activity is a hallmark of transitions from periods of quiescence to periods of high arousal or motor output, it is unclear whether large-scale circuits spanning multiple cortical areas also exhibit changes in coordination across state transitions.…”

“…However, the development of receptor-based fluorescent indicators that directly report ACh binding has opened new avenues for the exploration of neuromodulation. Here, we used two-color mesoscopic imaging 10 of the red-fluorescent calcium indicator jRCaMP1b 37 and the green-fluorescent ACh indicator ACh3.0 38 across the entire dorsal neocortex of the awake mouse to quantify the relationships between behavioral state, cortical activity, and cholinergic signaling. Our results demonstrate that, in contrast to traditional models, different behavioral states categorized by motor behavior are associated with distinct spatiotemporal patterns of ACh fluctuations and increased large-scale network synchronization.…”

Rapid fluctuations in functional connectivity of cortical networks encode spontaneous

“…However, these studies generally lack the temporal resolution to establish links between cortical signals and the continuously varying fluctuations in spontaneous behavior typically observed in awake animals. Here, we took advantage of recent developments in wide-field, mesoscopic calcium imaging 11 to monitor neural activity across the neocortex of awake mice. Applying a novel approach to quantifying time-varying functional connectivity, we developed a “graph of graphs” method to show that spontaneous behaviors are more accurately represented by fast changes in the correlational structure versus the magnitude of large-scale network activity.…”

“…Here, we sought to investigate the relative contributions of cortical activity versus dynamic functional connectivity in behavioral encoding. We carried out widefield, mesoscopic calcium imaging 11 in awake, head-fixed mice expressing the red fluorescent indicator jRCaMP1b 17 (Figure 1a). Indicator expression was mediated by neonatal injection of wild-type mice with AAV9-Syn-jRCaMP1b (Supplemental Figure 1, see Methods) 18,19 .…”