We caricature electrical activity of the gravid uterus by a 2D excitable medium with FitzHugh Nagumo kinetics, and estimate a pseudo-electro hysterogram (EHG) by methods of Plonsey et al. (1988). d u —- = (D(x , y) u′)′ – k u(u – ua)(u – 1) – v + I(x, y) d t d v —- = ε(G u – v) d t where u and v are the variables, ′ is differentiation with respect to space, and the input current I, and diffusion coefficient D at each point in the medium are assigned a value around a given mean using a normal distribution with standard deviation of 0.15. We consider the two cases separately (Fig 1). For irregular I, the four behaviours are ( i ) no or little propagation activity ( ii ) bursting ( iii ) moderate but synchronized activity and ( iv ) high and synchronized activity. For irregular D the two behaviours are either no propagation activity, or propagation above a critical 〈D〉 . The pseudo EHG during bursting (region ii) has a low p.s.d. similar to that observed (Snowden et al. 2001). Synchronized and propagating bursting is obtained at high coupling and excitability.
University of Oxford (2004) J Physiol 561P, PC16
Communications: SYNCHRONIZATION AND BURSTING IN A SIMPLE VIRTUAL GRAVID UTERUS
Kharche,Sanjay ; Holden,Arun V; Smye,Stephen W; Snowden,Steve ; Simpson,Nigel A B; Clayton,Richard H; Walker,Jimmy J;
1. Computational Biology Laboratory, School of Biomedical Sciences, University of Leeds, Leeds, United Kingdom. 2. Medical Physics, St. James' University Hospital, Leeds, United Kingdom. 3. Paediatrics, Obstetrics and Gynaecology Unit, Leeds General Infirmary, Leeds, United Kingdom. 4. Department of Computing, University of Sheffield, Sheffield, United Kingdom. 5. University Dept. of Obstetrics and Gynaecology, St. James' University Hospital, Leeds, United Kingdom.
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Figure 1. A power spectral density (p.s.d.) normalised to peak power of clinical EHG data. At month 8 during late pregnancy (continuous line) has a low frequency component (0.2-0.45 Hz) and approximately 1 week before birth during advanced late pregnancy (dashed line) has an additional high frequency component (0.8–3 Hz). B normalised p.s.d. of pseudo-EHGs from simulations where I was irregular. Low excitability and low coupling curve (I = 0.2 D = 0.2) peaks at 0.01 (continuous line). High excitability and high coupling curve (I = 0.5 D = 0.5) curve peaks at 0.02 (dashed line). There is an increase in high frequency power. C changes in synchrony and excitability as a function of I and D with I irregularly distributed. D same as in C but with irregular D.
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