Visualizing mammalian brain area interactions by dual-axis two-photon calcium imaging

Abstract

Lecoq and colleagues introduce a two-photon microscope with two articulated arms that can image nearly any two brain regions, nearby or distant, simultaneously. They validate this new system by imaging calcium signals in two visual cortical areas in behaving mice, and find evidence suggesting activity fluctuations can propagate between cortical areas Fluorescence Ca2+ imaging enables large-scale recordings of neural activity, but collective dynamics across mammalian brain regions are generally inaccessible within single fields of view. Here we introduce a two-photon microscope possessing two articulated arms that can simultaneously image two brain areas (∼0.38 mm2 each), either nearby or distal, using microendoscopes. Concurrent Ca2+ imaging of ∼100–300 neurons in primary visual cortex (V1) and lateromedial (LM) visual area in behaving mice revealed that the variability in LM neurons' visual responses was strongly dependent on that in V1, suggesting that fluctuations in sensory responses propagate through extended cortical networks.