Fig. 2

Fig. 2 During spontaneous swim bouts, tectal neurons receive motor-related phasic inhibition.

a Example recording of inhibitory membrane currents (I_post) during spontaneous fictive swim activity. Swim events (bursts in the MNR_ipsi and MNR_contra traces) are closely followed by short-lasting, large inhibitory postsynaptic currents (IPSCs) in a tectal neuron. Holding potential was +10 mV. b Magnified view of the second event from (a). IPSC charge was measured in a 250 ms window (dotted rectangle). Delay (Δt) was measured between the first burst in the swim bout and the IPSC onset. MNR traces are overlaid with traces representing their standard deviation (see Methods). c Histogram of inhibitory charge transfer in tectal neurons associated with spontaneous swimming (individual cell averages from n = 56 neurons). Dashed curve: Gaussian fit to the left peak of the charge histogram. In the majority of cells (n = 32), inhibitory charge transfer was larger 0.8 pC (bars co-labeled in magenta), indicating non-negligible inhibitory swim-related input. d Histogram of delays between swim onset and IPSC onset. Individual cell averages from n = 32 cells with non-negligible inhibitory swim-related input. e Scatter plot of swim-related transient hyperpolarization measured in current clamp (ΔV_m) and IPSC charge transfer measured in voltage clamp from a subset of cells in (c) where both modes of recording were applied (n = 21; 8 cells with IPSC charge <0.8 pC, 13 cells with charge >0.8 pC). ΔV_m and IPSC charge are negatively correlated (r_Spearman = −0.65, p = 0.002, Spearman rank correlation), which also holds if the two rightmost data points are excluded from correlation analysis (p = 0.014, see Supplementary Fig. 1e). Source data are provided as a Source Data file.