Figure 3.

Long-lasting intrinsic plasticity alters firing properties. A, Six overlaid firing responses (the first 200 ms are illustrated) of a barrel cortex neuron to injection of current pulses (+0.4 nA, 500 ms) before (top traces) and during (bottom traces) LLPIE. The dashed line indicates the onset of the current injection. The corresponding raster plots of the first spikes (25 successive trials) are shown at right. B, Mean values of first spike latency and jitter before and after LLPIE induction (n = 18 neurons). C, DC superimposition of the first spikes evoked by current injection in control (black traces, n = 3) and after conditioning (blue traces, n = 3) showing that LLPIE was associated with an increase in the slope of membrane depolarization preceding the first action potential and with a lowered voltage spike threshold. Spikes are from records in A and truncated for convenience. Population analysis (right, n = 14 RS neurons) reveals a postconditioning decrease in the first spike threshold in all computed cells. D, Six overlaid firing responses of a barrel cortex neuron to injection of +0.2 nA current pulses before (top traces) and after (bottom traces) LLDIE induction. The corresponding raster plots of the first spikes (22 successive trials) are shown at right. E, Mean values of first spike latency and jitter before and after LLDIE induction (n = 12 neurons). F, DC superimposition of the first spikes evoked by current injection in control (black traces, n = 3) and after conditioning (orange traces, n = 3) showing that LLDIE was correlated with a decrease in the slope of the prespike voltage trajectory and with an augmented voltage spike threshold. Same cell as in D is used. Population analysis (right, n = 9 RS neurons) reveals a significant increase in the first spike threshold after induction. ***p < 0.001.