Figure 2. Action potential firing patterns of layer 5 pyramidal neurons in response to somatic current injection.

Discharge patterns of three neurons in response to steps of positive current (lower superposed traces). The holding potential is shown below the lower voltage traces. Note that in the regular firing neuron a single action potential is evoked at threshold current intensity. In weak and strong burst firing neurons, however, a high frequency (> 250 Hz) burst of action potentials is the threshold response. Bursts of action potentials were repeated throughout the duration of current pulses in strong, but not weak, burst firing neurons. The number of action potentials composing a burst, however, decreased with time in strong burst firing neurons.