Sometimes we get lost in some concepts and definitions then forget the purpose and the fundamentals. Some researches always say brain signals... brain signals... in general, in the aspect of EEG functions, brain signal means brain wave. Brain wave is defined in wave-type. It is not touchable but in huge scale and enormously amplified condition, can lead to a disaster.

Each element has characteristic to be described. We as humans are not excepted. We can be described in various aspects respecting to be more discovered. These features may be changed during time! Based on these changes you describe the creature.

For each characteristic you need a receiver. The characteristic such as temperature is defined assisted by thermometer as well as brain waves but using EEG. Furthermore, for instance, the signals of brain resulted by blood oxygen level are recorded by MRI. We evaluate the subject based on the changes of blood oxygen level confronting specific function. It seems that we as engineer are trying to analyze extracted signals or data in order to do discovery assisting these devices.

To detect human temperature, the thermometer is put in the mouth and the chemical substance inside the device is impacted by body’s temperature and reach to certain number. The number on the thermometer presents body’s temperature. The number is a signal. It itself doesn’t mean. We need to put it in determined and described list depicting the circle of our fundamental medical knowledge. The number can be considered as a constant or can be put in a fuzzy system. Depending on the question why we are asking about the temperature, the data or signal is considered differently. The question leads how to see the data. Some information is definite. Like fundamental knowledge. They are the best facts resulted by lots of observations. Till now, there has not been any statement to reject them. These facts assist researches to keep forward.

Brain waves are resulted by the actions inside the brain. Example; when you knock the wall, you hear Boom sound. This sound is resulted by knocking the wall. The stronger, the highest sound. Sound is a wave. A wave which spreads into the air in three dimensions. You cannot see it but your ear as a receiver catches this wave; if it is in human’s domain. Electrical devices are equipped by sensors acting like ear. They receive wave and present it in two-dimensional environment to be easy to understand. Oscilloscope... if you want to know how the sound turns to graphical environment, you need to review oscilloscope primary concepts. I will describe it a bit later. The graph resulted by oscilloscope seems pretty ugly... we need to clean it. We apply some filters to remove noises. In the air, the Boom sound was not the only wave at that moment when recording. It seems our receiver recorded more waves. The other waves are carried by our Boom sound wave. These extra waves disturb our procedure to analyze the behavior of data obtained from that creature (knocking on the wall). 

Is it really important to know what was the reason of knocking?? Not for now... We only assume that it must be a hand just knocking. Maybe the sound was created by kicking or using a crowbar... depending on our question, we keep forward. Right now, we have the consequences of the function; knocking created by anything!!! We can concentrate on the side effect of knocking.

Inside the brain, lots of functions exist. They are creating lots of different shapes of knockings. We do not know what are the causes. In some cases, we have found some relations between knocking and data obtained by receivers. Brain waves are recorded by EEG and are printed as graphs in two-dimensional environment. These functions are somehow connected to the receivers not always. Genetic and other factors are effective. In BCI researches, we first estimate each function for each consequence or side effect or signal or data, here brain wave.

 In research scale in BCI system, various types of functions are considered. These functions are defined based on something which apply on the creature (here, human). The function related to movement is defined for the person who has movement disability. This type of function leads some specific parts of brain be active more than others. This importance has been considered as a fundamental or something contracted between researches in medical science and neuroscience. It resulted by observations according to different experiments using MRI and EEG as well or other techniques. Thus, we accept it and keep forward. We want to analyze brain waves confronting specific function. In next document, I will describe a little about oscilloscope and noise and filter as well as some brain functions in BCI.

TATA. Oct, 28, 2020. 13:24