Extended Data Fig. 6: Functional imaging of OB axons in PCx via axonally targeted GCaMP6s.
From: Structure and flexibility in cortical representations of odour space
a, Left, whole-mount depicting Tbx21-Cre-dependent expression of AAV PHP.eB hSynapsin1-FLEX-axon-GCaMP6s in OB projection neuron axons. GCaMP6s fluorescence is broadly distributed across piriform cortex. Right, coronal sections depicting GCaMP6s signal (green) in the mitral cell layer across the entire anterior-posterior extent of the olfactory bulb and cortex. Inset, bottom, GCaMP6s-labelled axons shown coursing through PCx L1a. Bottom left, en face image of L1a depicts dense and uniform distribution of axonal boutons. b, Difference heat map of a typical field-of-view (FOV) depicting baseline and odour-driven fluctuations in GCaMP6s signal. The strongest activation (light colour) is associated with axonal boutons. c, Time-averaged fluorescence signal of FOV in b. Overlay shows segmented ROIs corresponding to axonal boutons depicting increases (red) or decreases (blue) in fluorescence, averaged over multiple presentations of a single odour from the tiled odour set. d, Example average fluorescence from several boutons in a. Grey bar indicates odour delivery period, scale bar indicates response amplitude. For clarity, fluorescence time courses for each example bouton are offset along the y axis. e, Example bouton responses for the tiled odour set. Each row represents the trial-averaged response of a single bouton for two seconds during and after odour exposure (columns) depicted as z-scored ∆F/F0; rows are sorted hierarchically using correlation distance and average linkage. The functional group and carbon chain-length associated with each odour are indicated below each column; light-to-saturated gradient indicates progression from short-chain to long-chain odours. Note that, as has been observed previously for OB projection neurons, boutons exhibit a substantial amount of odour-driven suppression.
