(A) Morphological EM reconstruction of the CSDn arborizations used for a biophysical model consisting of 6056 compartments. (B) Somatic membrane potential changes in response to a white-noise current injection during an in vivo CSDn recording compared to responses of a passive compartmental model, to the same stimulus, fitted by optimizing three anatomical parameters, Cm (μF/cm2), gleak (S/cm2), and Ra (Ωcm), (C) An example of a model with well-fit somatic responses where a hyperpolarizing current injection in the AL resulted in highly localized voltage changes in AL only. A time series of voltage responses are shown for the soma, AL, and LH as gray traces near those structures. Cm = 4.8, gleak = 3094.3, and Ra = 149.0183. Horizontal scale bar = 5 ms and vertical scale bar = 5 mV. (D) A similar model where injection of the current in the AL causes a voltage change throughout a greater portion of the AL. Cm = 4.8, gleak = 2911.3, and Ra = 28.83. Scale bars as in C. (E) A sample model where current injection into the AL causes both somatic and LH voltage changes. Cm = 1.8,wgleak = 77.33, and Ra = 0.12. See Table 1 for full model properties .Scale bars as in C. (F) The proportion of voltage signal observed in the LH, AL, and cell body (CB) when voltage changes are induced in each region. The same model as in panel E was used to generate the data. Left, voltage steps are induced into the AL and voltage deflections are reported in the LH and CB. Right, voltage steps are induced in the LH and their effects are measured in the AL and CB. Horizontal scale bar = 10 ms and vertical scale bar = 10 mV. (G) A 2P image of basal GCaMP6s signal showing the effects of laser ablation in the CSDn LH neurite. (H) Basal GCaMP6s signals remain in the LH after laser ablation. (I) ΔF/F responses of CSDn neurites in the LH to a set of odorants before and after laser ablation. (J) A times series of the changes in calcium levels in response to odorants in (I). (K) Left, quantification of odor response amplitudes in CSDn LH neurites before and after laser ablation. Right, control responses when the contralateral processes of the CSDn where ablated. Left column, top to bottom, p=0.0187, p=0.0067, p=0.0154; Right column, top to bottom p=0.2298, p=0.8958, p=0.1611. *=p < 0.05, **=p < 0.01, n.s. = not significant and p>0.05, paired Student’s t-tests.