Figure 4.

Spatial displacement of Mi1- and Tm3-mediated inputs onto a single T4 (T4–12). (a) Bottom view of dendrites of the Mi1 (cyan) and Tm3 (magenta) neurons presynaptic to T4–12, overlaid on the array of L1 axonal terminals (yellow). The color saturation for each dendritic arbor reflects the number of synaptic contacts made onto T4–12 (see (b, d)). The arrow shows the displacement from the Tm3 center of mass to the Mi1 center of mass computed as illustrated in (e). (b) Side view of T4–12 and its presynaptic Mi1s and Tm3s. Direction preference for a T4 (colored to match the directional preferences in (e)) is determined by the lobula plate arborization layer of the axon terminals. (c) Enlargement (dashed rectangle) from (a) showing reconstructed neurites of Mi1s, Tm3s and L1s (without the weighted colors in (a)), and their synaptic contacts (L1 → Mi1: blue; L1 → Tm3: red). (d) Reconstructed dendritic arbor of T4–12 with synapses from Mi1s (blue) and Tm3s (red). (e) Cartoon of inputs to a single T4 through Mi1s and Tm3s. Mock synaptic weights illustrate how the receptive fields were computed. The center of mass of Mi1 (or Tm3) component, blue (or red) circle, is computed by placing the mass corresponding to the compound synaptic weight from L1 through Mi1 (or Tm3) to T4 at the center of the corresponding column. Scale bars: (a) 8 μm, (b) 8 μm, (c) 1 μm, (d) 4 μm.