Figure 6

Inverse analysis of an experimentally recorded ST map. Panel A displays an ST map obtained fluoroscopically from a mouse in vivo (modified from [13] and used with permission from The American Physiological Society). A selected window (dashed square) is magnified at right (inset). The overall pattern is that of series of frequent and regular contractions in the duodenum. Two arrows indicate principle axes of the patterns; one with a steep slope ('a') and a second with a more gradual slope ('b'). Panel B displays a simple type of a simulated contraction pattern in which a burst oscillated at a width and a frequency similar to that in panel A. These oscillatory contractions also propagated in the aboral direction as indicated by arrow 'a' with a slope similar to that in the inset. Arrow 'b' however is horizontal as all oscillations occur at the same time, implying that the in vivo contractions did not occur simultaneously. In panels C, the contractions oscillated and propagated in various sequences. In C1, the contractions did not contract simultaneously, but one after the other, stepping forward in the aboral direction (indicated by '1', '2' and '3'). With this scenario, slope 'a' is similar but slope 'b' is directed in the aboral direction, opposite to that measured in vivo (inset). Scenario C2, in which the contractions occurred in the opposite sequence ('3', '2' and '1'), does produce a slope 'b' similar to the original one. Scenarios C3 and C4 repeat scenarios C1 and C2 but with propagation in the oral direction, creating a different slope of arrow 'a'.