Figure 4.

Ventral vestibulospinal neurons respond to impulse stimuli in a nondirectional, magnitude-independent manner. A, Voltage trace corresponding to feedback from galvanometer during a 10, 15, and 30° impulse step to the left. B, Feedback trace during the impulse step to 30°. C, Normalized fluorescence traces for all trials of one neuron during baseline and response to an ipsilateral 30° impulse step. Note the lower scale on the vertical axis relative to Figures 1–3. D, Distribution of coefficients of variation of peak fluorescent intensity across 30° step trials for responsive neurons (n = 22 neurons). E, Mean normalized fluorescence traces for one neuron during baseline and response to an ipsilateral and contralateral impulse step of varying magnitudes (10, 20, 30°). F, Mean peak ΔF/F responses across all responsive neurons for ipsilateral and contralateral impulse steps of 10, 15, and 30° magnitudes. Error bars indicate ± SEM. G, Distribution of directionality indices (see above, Materials and Methods) across all responsive neurons. H, Spatial location of impulse-responsive (green) or nonresponsive (gray) vestibulospinal somata relative to the Mauthner neuron lateral dendrite in microns. I, Distribution of dorsoventral position of vestibulospinal neuron bodies relative to the Mauthner lateral dendrite in microns for impulse-responsive (green) and nonresponsive (gray) neurons. Solid lines represent the distribution of all responsive or nonresponsive neurons across all fish. Error bars represent ± 1 bootstrapped SD.