Fig. 3 Single Spikes in Single Somatosensory Neurons Can Trigger Escape Behaviors
(A) By closing the microscope's epifluorescence-field aperture, illumination could be restricted to single cells in sparsely labeled embryos. Red channel: illumination light; green channel: ChR2-expressing Rohon-Beard neuron. The scale bar represents 20 μm.
(B) Stimulation of a single cell reliably evokes a behavioral response. One hundred millisecond stimuli were delivered at different positions along the A-P axis of the fish, and behavioral responses were monitored by watching the local contraction of the muscle. A-P displacements are given relative to the field in which the cell was located in the center of the illumination spot (0 μm). The number of successful trials (out of five) at each field is given at the bottom of each panel, above the displacement value. At -80 and +80 μm, the cell has moved completely out of the illumination spot. The scale bar represents 10 μm.
(C) Data pooled for five cells in five different fish that showed single-cell responsiveness. Mean ± SEM response probabilities are shown at several A-P displacements.
(D) Dependence of behavior probability on pulse duration. Cells identified as being sufficient to elicit a behavior were stimulated five times at each of several different pulse durations, and the behavioral output was monitored. Differently colored traces represent different cells (n = 5 cells in four fish; includes three trigeminal and two Rohon-Beard neurons).
(E) Number of spikes evoked by light pulses of different durations. Data show the probability of a given number of spikes occurring at a given pulse length and are pooled from six neurons. Pulses of 10 ms or less never evoked more than a single spike.
(F) Single spikes are reliably evoked by 5 ms light pulses (blue bar) in a trigeminal neuron. Stimuli were delivered at 0.2 Hz.