Fig. 2: Characteristics of electrical activities in smooth muscle over 1 mm and 30 mm electrode separation distances.

Plots a–K and l–v pertain to analysis of fluid distension at 1 mm and 30 mm electrode separation respectively, following fluid distension. Plots a, l: These plots contain the raw data for the proximal and distal colons, represented by the red and blue lines respectively. Plots b, m: These plots contain the WCOH (absolute value) between the proximal and distal colons. In both the 1 mm and 30 mm examples, the period of increased activity at ~2 Hz in plots a, l is also reflected in the WCOH. Plots c, n These plots contain the CWT (absolute value) for the proximal colon, and plots d, o for the distal colon. The increased activity at ~2 Hz in plots a, l is reflected in these plots at ~2 Hz. Plot e, p The red and blue lines are traces of bandpass filtered data (filter limits 0.5 and 3.5 Hz) for the proximal and distal ends respectively. The plots are zoomed in during the period of increased activity at ~2 Hz. The vertical bars denote the peaks of the oscillations; in the 1 mm example, the peaks are almost coincident, whereas in 30 mm example, these peaks will usually be separated further. Plot f, g, q, r In both plots, a window (length 3 sec) has been slid over the bandpass filtered data in plots e, p. In each window instance, the likelihood that the data have a particular frequency is calculated; these plots display the log-likelihood. The frequency range for which the likelihood is calculated is given by the y-axis—in these examples from 1 to 2.8 Hz. Plot h, s These plots overlay the frequency maximizing the log-likelihood function for the proximal (plots f, q), and distal colon (plots q, r). In these plots, the frequencies maximizing the likelihood functions are close during propulsion and diverge elsewhere. Plot i, t In these plots, a window (length 3 sec) has been slid over the bandpass filtered data in plots e, p. In each window instance, the cross correlation between the proximal and distal colons is calculated, which these plots display. During propulsion, the cross correlation is periodic with periodicity ~0.5 seconds, corresponding to a frequency of ~2 Hz. Moreover, the periodicity of cross correlation increases with time, which is consistent with the decrease in frequency estimates displayed in plots h, s. Plots j, k, u, v In these plots, a window (length 3 sec) has been slid over the bandpass filtered data in plots e, p. In each window instance, the auto-correlation function is calculated; plots j, u contains the auto-correlation function for the proximal colon, and plots k, v the auto-correlation function for the distal colon. During the period of activity, the auto-correlation functions are both periodic with the same periodicity, which is consistent with the frequency estimates displayed in plots h, s.