Fig. 4.

An example of a post-stimulus time histogram (PSTH) obtained from an E-neuron in the Bötzinger region shows the method of analysis used to determine the presence of synaptic inputs to the recorded neuron from the PB subregion stimulus. The average post-stimulus discharge frequency is calculated as number of (spikes/ bin)/(bin-width)/(number of trigger events). A change in the probability of the neuron discharging due to the stimulus is shown by a deviation in the histogram from a baseline level. This baseline level typically occurs during the last 50-ms of the histogram when the neuronal activity is unperturbed by the stimulus. The average discharge frequency and standard deviation were calculated during the last ~50 ms of the PSTH (right) and used to set reference levels for the mean ± 2 SDs shown as dash horizontal lines. A 5-point running average was used to smooth the data (red line). The times of significant deviations were marked (thick black line segments superimposed on the baseline level). For each of these marked regions, the latency, duration, average frequency during the deviation relative to baseline and the area of the deviation were calculated (shaded region). The first few ms of the PSTH shows the shock-artifact zone that results from sorting out the stimulus artifact from the neuronal recording.