Figure 9. Background does not diminish the distal Ca²⁺ spike, but may reduce its inward drive at the soma.

The distal Ca²⁺ spike triggered by tuft input is compared with (at right) and without (at left) the simulated background. The voltage axis is aligned for both records; the discrepancy in resting potential levels for both soma and dendrites arises from the net background synaptic drive. Note that while the background had little effect upon the Ca²⁺ spike's amplitude and duration in the distal apical trunk (green trace), it profoundly diminished the after-depolarizing potential driven at the soma (arrow).