Figure 4.

Effect of somatic stimulation frequency on dendritic Ca²⁺ spike occurrence. A, A simulated train of brief suprathreshold pulses at frequencies of 100 Hz (left) and 149 Hz (right) (top) was injected into soma eliciting a train of Na⁺-APs (black, below). Only the 149 Hz train evoked a dendritic Ca²⁺ spike (red, bottom). B, Intracellular dendritic Ca²⁺ concentration during somatic stimulation at 100 Hz (left) and 149 Hz (right), respectively. Blue lines indicate the Ca²⁺ concentration at each time instant of the dendritic voltage traces indicated in A. C, Integrated area below the dendritic voltage traces as a function of the Na⁺-AP frequency with (blue) and without (black) the I_h current. CFs of 105 Hz and 149 Hz were obtained when I_h was present and absent, respectively. D, Observed shift in CF after blocking I_h for 11 cells (black circles, numerically estimated from Berger et al., 2003) and simulated with the model (blue diamonds).