Detecting Phase Coupling of Gastric Interdigestive Pressure Activity via Diagonal Slice Spectra

We propose a new analysis method to detect phase coupling behaviour of the human gastric interdigestive pressure wave that has been acquired by a telemetric capsule-like mini-robot. The method is referred to as diagonal slice spectra, which are the Fourier transforms of the diagonal slices of the triple correlation and can detect the phase coupling and coupled components respectively. It is shown that nonlinear quadratic phase coupling occurs during gastric contraction (phase II), whereas no distinct phase coupling occurs during gastric motor quiescence (phase I).