An optimization formulation for characterization of pulsatile cortisol secretion.
An optimization formulation for characterization of pulsatile cortisol secretion.
复制标题
DOI：
10.3389/fnins.2015.00228
复制
发表时间：
2015
影响因子：
4.3
通讯作者：
Brown EN
中科院分区：
文献类型：
--
作者：
Faghih RT;Dahleh MA;Brown EN
皮质醇被释放，将信息传递给细胞，以调节新陈代谢和对压力和炎症的反应。特别是，皮质醇以脉动信号的形式释放。这种低能量的信令方法似乎比连续信令更有效。我们假设在垂体前叶有一个控制器导致皮质醇的脉动性释放，并提出了这种控制器的数学公式，这导致了脉冲控制而不是连续控制。我们推测，该控制器将导致皮质醇分泌的分泌事件的数量降至最低，这是一种最小化皮质醇分泌所需能量的方式；该控制器将血液皮质醇水平维持在特定的昼夜范围内，同时遵守皮质醇分泌的一阶动力学。该控制器采用ℓ0范数代价函数，并采用加权ℓ1范数极小化算法来求解该优化问题。我们用四个例子来说明这种方法的性能：(I)实现脉冲控制的玩具问题，(Ii)实现生理上可信的脉冲式皮质醇释放的两个例子，(Iii)脉搏数不在健康受试者的生理合理范围内，而皮质醇水平在所需范围内的例子。这一新的方法导致了脉冲控制，其中脉冲和获得的血液皮质醇水平具有昼夜节律和极端节律，这与皮质醇分泌的已知生理学相一致。建议的配方是开发治疗皮质醇缺乏症的间歇控制器的第一步。这种受生物启发的脉冲控制器可用于神经科学应用的脑机接口设计中的非连续控制器设计。
Cortisol is released to relay information to cells to regulate metabolism and reaction to stress and inflammation. In particular, cortisol is released in the form of pulsatile signals. This low-energy method of signaling seems to be more efficient than continuous signaling. We hypothesize that there is a controller in the anterior pituitary that leads to pulsatile release of cortisol, and propose a mathematical formulation for such controller, which leads to impulse control as opposed to continuous control. We postulate that this controller is minimizing the number of secretory events that result in cortisol secretion, which is a way of minimizing the energy required for cortisol secretion; this controller maintains the blood cortisol levels within a specific circadian range while complying with the first order dynamics underlying cortisol secretion. We use an ℓ0-norm cost function for this controller, and solve a reweighed ℓ1-norm minimization algorithm for obtaining the solution to this optimization problem. We use four examples to illustrate the performance of this approach: (i) a toy problem that achieves impulse control, (ii) two examples that achieve physiologically plausible pulsatile cortisol release, (iii) an example where the number of pulses is not within the physiologically plausible range for healthy subjects while the cortisol levels are within the desired range. This novel approach results in impulse control where the impulses and the obtained blood cortisol levels have a circadian rhythm and an ultradian rhythm that are in agreement with the known physiology of cortisol secretion. The proposed formulation is a first step in developing intermittent controllers for curing cortisol deficiency. This type of bio-inspired pulse controllers can be employed for designing non-continuous controllers in brain-machine interface design for neuroscience applications.