2. Biofeedback from control theory perspective

 

Biofeedback uses sensors that can monitor varieties of different physiological processes. The ongoing information is then fedback to the person in visual or auditory form. With this information, the person can become aware of these processes and can then learn to control them in a more consistent manner with healthy functioning.The following are some of the biological responses that can be measured and fedback to the person (hence the term Bio-feedback)

 

1.Muscle Tension

2.Skin surface temperature

3.Heart rate

4.Blood Pressure

5.Brain wave activity

6.Sweat gland activity.

 

The biofeedback resembles the closed loop control system in control theory. A closed-loop control system is one in which an input forcing function is determined partly by the system response. The measured response of a physical system is compared with a desired response. The difference between these two responses initiates actions that will result in the actual response of the system to approach the desired response. This in turn drives the difference signal toward zero.A closed-loop control system can be represented by the general block diagram as shown in Figure 1. A Biofeedback system can also be similarly modeled in terms of input from sensory organs, brain and Biofeedback output. A typical biofeedback circuit is shown in Figure 2. The sensory organs are responsible for biofeedback stimulation. Biofeedback stimulates the nervous system concomitantly with homeostatic regulation of the body through hormonal activation. The role of the brain is central, adjusting the system in accordance with the biofeedback stimulus received from the sensory organ. Without the brain there would be no output response. Biofeedback stimulates the subconscious part of the brain, and depends upon the nature of stimulus received from the sensory organ in the subject's particular current environment. Both the conscious and subconscious parts of the brain are important in biofeedback.In Figure 2, transduction phase reflects phyiological changes caused by hormonal release consequent on simulation. Homeostasis is the set of processes by which the constant or static conditions are maintained within the internal environment of a subject; a homeostat is a controller involved in maintaining homeostasis.