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Fig. 2 Speed-related recruitment of the two nMLF neuronal populations
(A) Upper panel shows the experimental setup with head-fixed adult zebrafish in which the tail movement is monitored via a video camera, while the calcium activity of nMLF neurons is examined using a two-photon confocal microscope. The two lower panels illustrate spontaneous swimming at slow speed/low amplitude (blue) or fast speed/high amplitude (orange).
(B) During slow swim episodes (tail movement trace indicated with a blue line in the upper panel) medial vGlut2+ nMLF neurons were activated bilaterally, whereas the lateral vGlut1+ neurons were not recruited (second panel). The dashed black horizontal line indicates the highest amplitude reached during fast speed/high amplitude swim in (C). Third panel shows the increase in calcium activity in medial vGlut2+ and the lack of activity in lateral vGlut1+ nMLF neurons. Last panel shows the calcium activity at two time points (1 and 2) indicated by the white dashed lines in the panel above.
(C) During slow swim episodes associated with small tail movements (tail movement trace indicated with a blue line in the upper panel), only medial vGlut2+ nMLF neurons were activated bilaterally. During mixed episodes with slow and fast swim, the lateral vGlut1+ neurons were only recruited during fast swimming associated with large tail movements (indicated by the orange line in the upper panel). Third panel shows the changes in calcium levels in medial vGlut2+ and lateral vGlut1+ nMLF neurons on the left and right sides. Last panel shows the calcium activity at two time points (1 and 2) indicated by the white dashed lines in the panel above.
(D) Only medial nMLF neurons were recruited during slow swim.
(E) Both medial and lateral nMLF were recruited during fast swim.
(F) Medial vGlut2+ nMLF neurons did not increase their activity with increased swim movement amplitude.
(G) Lateral vGlut1+ nMLF neurons increased their activity with increased tail movement amplitude during swimming.