Modeling the daily rhythm of human pain processing in the dorsal horn
Fig 4
Daily rhythm in the modulation of pain sensitivity: Experiments and model.
A: Prototypical human “daily pain sensitivity” (i.e., daily changes in pain sensitivity relative to mean pain sensitivity) function (f(x) = 11sin(0.25x + 2.8), where x ∈ [0, 24] hours) fitted to (symbols) data (R2 = 0.73 and RMSE = 4.69) from four experimental studies of pain responses. For more details and sources of these data, see [6]. B: Daily modulation of the stimulus-induced firing rate of the afferent fibers modeled by Eqs (4) and (5). Top(bottom) panel displays the daily modulation of the peak stimulus-induced firing rate of the Aβ- (C-) fibers. In the bottom panel, the blue curve represents the effective modulation of the C-fibers including Aβ-dependent presynaptic inhibition. The x-axis refers to hours since the typical or scheduled morning wake time.