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Fig. 2 | BMC Biology

Fig. 2

From: Synchronization of inspiratory burst onset along the ventral respiratory column in the neonate mouse is mediated by electrotonic coupling

Fig. 2

Neuronal onsets are tightly synchronized along the VRC. A.i Lag was estimated as the interval between steep luminance rise in individual somatic Ca2+ transients and rise in the rectified integrated motor output. A.ii Heat map of neuronal lags ordered according to median ranking of onset times over 102 respiratory cycles. A clear gradient from black to beige highlights the fact that most cycles approximated the median ordering. Onset ordering was qualitatively different in a subset of inspiratory bursts indicated by contrasting vertical stripes. A.iii Analysis of ranked onset times contained in the green rectangle in A.ii. Raster plot of onset times ordered according to the median activation sequence; cycles significantly correlated with median ranking of onsets (“Typical,” orange bars) were interspersed with atypical onset sequences (light and dark blue bars). A.iv Principal component analysis reveals that typical lag rankings clustered (lower right), but a smaller cluster associated with alternate lag rankings indicates that alternate rankings also displayed stereotypy. Colored dots indicate typical and atypical breaths shown in A.iii. Black dot indicates median lag rank. B.i Rank correlations of individual inspiratory burst onset ordering with median rank ordering. Cycles whose ordering is significantly different are shown as blue points. B.ii Pooled data from 22 experiments reveals that most (88.8%, orange histogram) inspiratory onset sequences were not significantly different from their respective median ranking of lags. B.iii Standard deviations of typical and atypical inspiratory bursts are not significantly different, suggesting that atypical inspiratory bursts did not result from failed network synchronization. B.iv Most (77%) of the 11.2% of cycles categorized as alternate are uncorrelated with one another. C.i Anatomical location of earliest neurons for the experiment shown in A (lags color-coded as in A.ii) reveals that they span from pFRG/RTN to caudal preBötC. C.ii Spatial distribution of the 10% earliest ROIs (blue points) reveals that while a slightly higher proportion of earliest ROIs were located in the vicinity of pFRG/RTN, earliest ROIs were distributed along the entire ventral respiratory column. PBC/VRG, preBötC/ventral respiratory group; NA, nucleus ambiguus; PiCo, post-inspiratory complex; pFRG/RTN, parafacial respiratory group/retrotrapezoid nucleus

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