Figure 2.

Spatial Ca²⁺ gradients strongly depend on type of model implementation. Panels (A–C) show maps of the integrated calcium levels in the dendrite during a spontaneous burst of Ca²⁺ spikes (panel D). The dendritic branches are color coded to show the integrated calcium levels using a 20 ms window around the peak Ca²⁺ concentration of the first dendritic Ca²⁺ spike. The color scales used in these maps are nonlinear (using histogram equalization) to enhance the contrast. (A) Single Ca²⁺ pool model using SP_old mechanism results in homogenous Ca²⁺ levels. (B) Single Ca²⁺ pool model using SP_new mechanism results in variable Ca²⁺ levels. (C) Detailed Ca²⁺ dynamics model with buffering and 1D diffusion results in variable Ca²⁺ levels with larger Ca²⁺ gradients. (D) Voltage traces show the first spike of the Ca²⁺ burst for each model in all dendritic compartments for the 3 different models (see color code in Figure). The inset shows complete traces. (E) The underlying Ca²⁺ and K_Ca currents (recorded from all dendritic compartments) for the Ca²⁺ spike of the three different models (see color code in Figure).