Figure 1.
Morphological analysis of Drosophila vs. Calliphora HS cell dendrites.
(A) Comparison of size between the blowfly (Calliphora) and the fruit fly (Drosophila); ruler has mm markings. (B) Superposition of the HSN (green) and the HSE (red) in a Lobula Plate of Calliphora. On the right side, a rendering of the full reconstructions of both cells (HSN – green and HSE – blue) within the marked boundaries of the reconstructed Lobula Plate is depicted. (C) Similar setting for the HSN and HSE cells (both are green since they both express GFP) in a brain of Drosophila with corresponding reconstructions (HSN – red and HSE – black) to the right. (D) Power law between branch point and total length densities, a power of 1/2 being indicative of optimal wiring for planar dendrites [33]. (E) Absolute scaling between total surface and total length. Crosses indicate population mean and standard deviation.
Table 1.
Scaling of global anatomical features.
Figure 2.
Morphological model to study the scaling properties of HS cells.
(A) Model error compared to standard deviation of experimental measures as a function of the balancing factor bf, the one parameter in the morphological model. To the right, sample model dendrites (lighter colours) with their respective real counterparts for Drosophila HSE (black) and HSN (red) and Calliphora HSE (blue) and HSN (green). (B) Diameter histograms for all cell types (same colours as in A) and best fits (grey lines) using the quadratic taper fit from our model [12]. Lower panel shows scaled diameters of Drosophila cells in comparison to Calliphora cells. To the right, sample Calliphora and Drosophila HSE dendrites comparing real and modelled diameters (in lighter colours).
Table 2.
Scaling of dendritic anatomical features.
Figure 3.
Signal conduction and dendritic integration in Drosophila and Calliphora HS cells.
(A) Experimental input resistance and membrane time constant measurements in Drosophila HS cells (dark grey −10 min.; light grey −30 sec. after breaking into the cell). The later measurements were used for estimating average values since the patch is more stable then. Two model parameter sets (black and orange) were used in the further study. (B) Morphoelectrotonic transforms of four sample cells where electrotonic lengths are mapped onto the segments of the branched structures [42] (orange box: second parameter set for Drosophila). (C) Same four cells as in B but with the amplitude decay from the dendrite root mapped onto the y-axis of the cells (top panels) and delays from the dendrite root (middle panels) and from selected dendrite tips (bottom panels). The Drosophila HSN cell results are shown for the second parameter set in orange.
Table 3.
Electrophysiological measures.
Figure 4.
Electrotonic analysis of a morphological model for scaling HS cells.
(A) Database of models generated by pairing either a sample Calliphora (blue box) or a sample Drosophila HSE axon (black box) to a synthetic dendrite obtained from a sample Calliphora HSE dendrite contour but scaled in overall size (surface) and in complexity (number of branch points). Upper left (blue box) and lower right (black box) model dendrites correspond to Calliphora and Drosophila dendrite measures respectively. (B) Corresponding to the morphological model databases in A, total electrotonic length is shown for Calliphora (left) and Drosophila (right) morphological models. Models with realistic morphologies for Calliphora (blue box) and Drosophila (black box) are in the same range but scaling surface area or number of branch points changes these measures.
Figure 5.
Visual responses in Drosophila and Calliphora HS cells.
Calliphora (left) vs. Drosophila (right) HSE cell model responses to full field visual stimulation (top) and full field sinusoidal conductance injections in the dendrite with the phase corresponding to the x-axis location of the conduction injection site (bottom). Cyan, orange and pink dots in top panels indicate dendrite tip, dendrite root and axon terminal locations respectively for which voltage time traces are plotted in bottom panels. Grey bars indicate stimulation region (top panels) and time onset of stimulation (bottom panels).