The term Biosignal refers to all the signals that are being generated in the human body or any other living organism or more specifically it is used to represent all those signals from living organisms that are monitored to obtain certain useful information. Primarily, the term refers to signals that are electrical in nature but, some non-electric signals are monitored as well.
Typically, the changes in potential difference across a certain tissue in the body are measured in case of bio-electric signals. Let us have a look at few of the properties of biosignals generated by the human body that are analysed to obtain information:
- In case of Electroencephalography, the activity of the human brain is monitored. Usually, at a synapse (junctions between the cells of the nervous system), flow of ions takes place. This results in the formation of various signals that are used by the body to transfer information. The voltage variations that are caused by these signals are recorded and thus, the activity of the brain is measured.
In Magnetoencephalography, the magnetic fields that that are produced by the variations of electric currents that form the brain activity are monitored. For this, devices such as SQUID (Superconducting Quantum Interface Devices) are used as they have high sensitivity. A large number of difficulties are faced one tries to measure the same as the ambient magnetic noise in urban areas is quite high. Even with the use of SQUID, about 50 thousand neurons need to be active at a given moment in order to measure the field.
- Galvanic Skin Response technique is used to measure the electric resistance offered by the skin. In it first, a random area of the skin is selected to measure establish the base resistance and then, the area in concern is studied in reference to the data that has already been obtained. As emotional arousal increases skin activity, it is generally used in polygraph tests.
- The Electrocardiograph is produced by recording the electrical waves that are produced by a person’s heart. The human heart produces these waves when it pumps blood into the body. These waves are measured by electrodes that are attached to the person’s skin. The rhythms that are produced by these heart beats are analysed in order to detect weaknesses in the heart muscles or some other abnormalities.
Electromyography is similar to Electrocardiography but, it is used for any muscles in the body and not the heart muscles in particular. Similar to the heart muscles, the muscles in other parts of the body also produce electric waves when they contract. Their abnormal activity can be detected by the fluctuations in the graph that are recorded.
Thus, the various signals produced by the body prove to be very useful in detecting any abnormalities that may be present in the body. Biosignal processing is also used in research to understand various activities performed by specific organs in ones body.