A unified mechanism for innate and learned visual landmark guidance in the insect central complex
Fig 5
EPG to PFL3 connectivity scheme.
A. Diagram of the EPGs to PFL3s connectivity that drives the steering. Each EPG makes inhibitory connection to two PFL3 neurons, one on each side. The strength of the synapse depends on the index of the EPGi as shown in B. The summed activity rates of the right and left PFL3 neurons are compared to obtain the CX steering signal. Finally, gaussian noise (ν = 0;σ = 10) is added to obtain the final steering command. B. (a) Synapse strength as a function of the index of EPGi, obtained from the connectomic approach (Fig 4B; [30]). Synapses are inhibitory and therefore multiplied by -1. Red lines represent the connection with the subset of PFL3s from the right part of the PB and green from the left part. Synapse weights are presented in a circular representation to show the correspondence with the EPG input geometry. Index 1 corresponds to the synapse between ellipsoid body tile EPG1, connected to the rear right FOV (-157.5°), and PFL31, and so on, through to index 8, the synapse between EPG8, connected to the rear left (157.5°), and PFL38. (b) Heatmap in the arena from 100 simulations in total. The data are normalized to the landmark direction (indicated on the right). (c) Final direction/position of each simulation (n = 100) with the cue placed in different positions around the arena, expressed in the cue reference frames. C. (a) Simulations (n = 100 for each shift condition) where EPG-PFL3 synapse weights were shifted for 1 cell to the right/clockwise (compared to B.). Results show the heatmap relative to the cue (top) of the 100 simulations. (b) Simulations (n = 100 for each shift condition) where EPG-PFL3 synapse weights were shifted for 1 cell to the left/anti-clockwise. Results show the heatmap relative to the cue (top) of the 100 simulations. (c)-(d) Equivalent to (a) and (b), respectively, with a 2 cells shift.