The UP state is associated with an increase in neuronal responsiveness and a decrease in spike latency and jitter. A, Example of intracellular recording from a layer 5 pyramidal cell with the injection of random-amplitude artificial EPSPs. B, The UP state is associated with a marked increase in neuronal responsiveness. C, Raster plots and peristimulus histograms for two different-amplitude EPSPs (26 and 40 nS) showing that, during the UP state, the latency and jitter are reduced. The late spikes that occur during the UP state are not included in the latency and jitter calculations because no comparable spikes occurred during the DOWN state (see Materials and Methods). D, The spike latency and jitter (SD of latency) decrease with increases in the amplitude of the injected EPSP. Both the spike latency and jitter are significantly smaller during the UP state in comparison with the DOWN state.