Action potential phase locking in response to current-based cosines. A, Response to current-based cosines at average firing rates of 2 spikes/s under low (i) and high (ii) conductance. Sinusoidal modulation at 8 Hz is indicated below the voltage traces. iii, Average spike–phase histogram in response to 8 Hz modulation at average spike rates of 2 spikes/s. Low conductance is shown in black, high conductance is shown in red. B, Response to current-based cosines at average firing rates of 8 spikes/s under low (i) and high (ii) conductance. Sinusoidal modulation at 8 Hz is indicated below the voltage traces. iii, Average spike–phase histogram in response to 8 Hz modulation at average spike rates of 8 spikes/s. Low conductance is shown in black; high conductance is shown in red. C, Vector strength versus modulation frequency plots for low (black) and high (red) conductance at average firing rates of 2 (solid squares) and 8 (open squares) spikes/s. Tested modulation frequencies were as follows: 0.1, 0.5, 1, 4, 8, 12, 20, 50, 100, and 500 Hz.