From decision to action: Detailed modelling of frog tadpoles reveals neuronal mechanisms of decision-making and reproduces unpredictable swimming movements in response to sensory signals
Fig 6
a-c. Neuronal activities on the left (top) and right (bottom) body side for one selected simulation of the CNS model near swimming termination. Central subpanels show neuron spike times vs their rostro-caudal position (vertical) and upper and lower subpanels display the voltage traces for different types of CPG neurons. (a) Swimming slows before spontaneous termination by synaptic depression at about 5.6 s after stimulation. In the left side dIN trace there is no rebound spike after the last reciprocal IPSP (red arrow). (b) To mimic the head skin pressure, 10 sensory tSp neurons on the left side are injected with a step current (duration 0.4 s, 0.2nA). Both tSp and MHR neurons fire rhythmically (the mean frequency 32.5Hz), inhibit CPG neurons on both sides and stop swimming. In this case some caudal dINs on the right fire after the start of the inhibition but there is no mn activity. (c) A single randomly selected MHR is injected with 5 equal DC current pulses starting at 2,500 ms (total duration 0.3 s, each pulse is 30 ms). The single MHR fires twice to each pulse, inhibits CPG neurons and this is sufficient to stop swimming. (d) Percentage of simulations where swimming was stopped by the activation of a single randomly selected MHR vs the onset time of the MHR’s current, green dot shows experimentally determined value of stoppings for 2.4 s onset.