Entrainment and coherence in biology.

Abstract

Byline: T. Srinivasan INTRODUCTION Coherence and chaos walk hand in hand in biological systems. Any living system is a complex entity interacting with the environment in many predictable and some unpredictable ways. Unpredictability stems from the fact that we are not able to understand the workings of the system. Thus, there is a need for mathematical and physical models for many functions of the body. For example, seemingly unrelated and chaotic behavior is considered in the function of neurons of the brain. Any coherent and correlated discharge of the neurons of the brain is considered unusual indicating need for close monitoring and possible intervention. However, for normal functioning of cardiac muscles, coordinated and systematic discharge of the neurons is necessary. Thus, in different parts of the biological system, different types of activities of the neurons are considered normal. ENTRAINMENT Entrainment is a process through which independent systems interact with each other. When two signals are close to each other in frequency, they fall into a single frequency. [sup][1] The signal could be from inside the body or from outside. For example, an external signal, optical or acoustic, derived from electroencephalogram could drive the brain rhythms (such as a waves) to optimum values. One of the most common entraining signal sources is the so-called Schumann resonance (SR). This resonance occurs as electromagnetic waves bouncing back and forth between the surface of the earth and the ionosphere. Ionosphere contains full of charged particles and behaves like a mirror for low-frequency electromagnetic waves. SR is the result of these oscillations, and the resonance frequency falls within the a range of the brain waves. is thought that this resonance is essential for normal human activity; it is possible that entrainment of biological signals between humans could be understood on the basis of SR. [sup][2] Further, chanting certain mantras seems to entrain some physiological functions in the body. It was observed that during both prayers and mantras, there was an increase in the synchronicity of cardiovascular rhythms when they were recited 6 times a minute. There was also an increase in baroreflex sensitivity. [sup][3] Since most tissues in the body are piezoelectric, it is possible to explain that chanting could elicit electrical activity that could drive other physiological signals into entrainment. Another example of entrainment is through thinking alone. Heart rate normally varies in a random fashion; heart rate variability (HRV) has come under intense study to determine cardiac response during stress. is possible to observe sympathetic and parasympathetic activities when we record HRV and its time and frequency domain transforms. Entrainment of HRV and respiratory rhythm is reported during pleasant and loving thoughts. [sup][4] The above two examples illustrate ways through which we could intentionally entrain two signals in the body; the physiological advantage of this type of entrainment is not clear yet. is likely this could be used for management of some abnormal rhythms of the body. COHERENCE AND SYNCHRONY Coherence is a measure of how close in phase two signals are to each other. If two signals increase and decrease in amplitude in exact phase, then the signals are said to be fully coherent. Any small perturbation and a minute change in temperature will destroy coherence. In a biological system, such coherences are rare. Froehlich in England had suggested that the body makes use of long range coherences for possible energy conservation and control. [sup][5] This well-received concept is not taken up for discussion in this paper. should be noted that synchrony is not necessarily coherence. Normally many events are taking place in the body - such as respiration, cardiac activity, and stomach motility - that are thought to be independent of each other. …