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. 2018 Apr 23;115(19):E4493–E4502. doi: 10.1073/pnas.1717022115

Fig. 4.

Fig. 4.

AVB-B electrical coupling drives the bifurcation in the B-type neuron dynamics. (A) Representative curvature kymographs in AVB-B gap junction-deficient or AVB-ablated worms when anterior bending activity was abolished. (B) Probability for inducing high-frequency midbody undulation when anterior bending activity was abolished. Pie chart summarizes the percentage of worm locomotor states. Error bars indicate 95% binomial proportion confidence interval. ***P < 0.0001, *P = 0.002, #P < 0.0001 (*compared with Ctrl, #compared with UNC-7 rescued in AVB). χ2 test. Strains for comparisons are as follows: control [Pacr-5::Arch; Punc-4::TWK-18(gf)], n = 113 measurements, 13 worms; unc-7 [unc-7(hp121); Pacr-5::Arch; Punc-4::TWK-18(gf)], n = 102 measurements, 21 worms; unc-9 [unc-9(fc16); Pacr-5::Arch; Punc-4::TWK-18(gf)], n = 116 measurements, 26 worms; AVB-ablated [Plgc-55(B)::miniSOG, Pacr-5::Arch], n = 40 measurements, 11 worms; UNC-7 rescued in AVB [unc-7(hp121); Pacr-5::Arch; Punc-4::TWK-18(gf); Psra-11::UNC-7], n = 86 measurements, 12 worms. (C) Optogenetic activation of AVB premotor interneurons could trigger forward locomotion. (Left) Optogenetic activation (Psra-11::Chrimson, n = 133 measurements, 11 worms), showing locomotion velocity with time; red light (635 nm, 12 mW/mm2) was turned on at t = 0. Gray traces represent individual trials, and shaded region represents SEM. (Right) Probability for triggering forward locomotion. (D) Optogenetic inhibition of AVB premotor interneurons could abolish forward locomotion. (Left) Optogenetic inhibition (Psra-11::GtACR2, n = 187 measurements, 21 worms), showing locomotion velocity with time; blue light (473 nm, 0.76 mW/mm2) was turned on at t = 0. Gray traces represent individual trials, and shaded region represents SEM. (Right) Probability for abolishing forward locomotion. Ctrl represents worms without feeding ATR. Error bars indicate 95% binomial proportion confidence interval; ***P < 0.0001, χ2 test. (E) Example traces of calcium dynamics of B-type motor neurons. Darker lines were smoothed data, using an exponential filter to reduce high-frequency noise. Upon light illumination that activated AVB interneurons, neighboring VB/DB motor neuron exhibited oscillatory yet anticorrelated calcium activities. To eliminate the proprioceptive coupling signal, we restrained the worm body region anterior to the imaging cells within a straight microfluidic channel. (F) Power spectral density of calcium dynamics using the smoothed data.