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 4
Activity of hexNs and neuronal mechanism of swimming initiation.
a-b. Six recordings of responses to head skin stimulation (black arrow) on the unstimulated side from the same hdIN (from Fig 6C and 6D in [24]). (a) Excitation ramps to threshold and firing leads to swimming (arrow shows first spike). (b) Excitation ramp does not reach threshold. c. Two recordings of a possible hindbrain sensory processing hexN neuron response to a trunk skin stimulation (at arrow; from Fig 3g in [9]). d. Recordings from model hexNs to a trunk stimulation (at arrow). e-f. The averaged ramp of 5 randomly selected model hdINs (e) and 5 experimentally (exp) recorded hdINs (f) (from Fig 6F in [24]) to a subthreshold trunk skin stimulation (at arrow). In the model, the ramp decays significantly by 1.5 s due to synaptic depression of hexNs interconnections. The strength of hexN->hdIN connection is selected to match the average hdIN potential. g-j. CNS model responses to trunk stimulation: swimming (g), no response (h); one sided activity (i); synchrony (j). Top and bottom subpanels show spike times of active neurons. The central panel shows the averaged voltage dynamics of hdINs on left (VL(t), blue) and right (VR(t), red) sides. Coloured dots indicate crossing the threshold (dotted line). In the case of swimming (g), the green area corresponds to swimming activity and the initiation time t* is the mean of hdIN spike times on right. NOTE: To make spikes of RB sensory neurons visible, we show them by black colour. k. Bar chart shows distribution of four responses for different connection probabilities between hexNs on opposite sides. For each probability we run 100 simulations with randomised connectivity and synaptic weights.