A Decadal Walk on BCI Technology: A Walkthrough

Electroencephalography Waves

Electroencephalography waves, is the futuristic concept in the field of Brain-Computer Interface technique with a medical image processing background. It’s defined as an electrical activity captured from the surface of the scalp with the help of metal electrodes and conducting medium. The analysis of EEG waves is giving new paths to in the field of neuroprosthesis and neurorehabilitation.

EEG is measured directly from the cortical surface (electrocardiogram) by using depth probes called electrograms. When there is a transfer of data from neuron to neuron a local current is being developed due to synaptic excitation of dendrites and that is being measured by EEG. All the recordable electrical activities is being generated in the human scalp region, the local current penetrates the skin, skull and other layers to be measured (Larsen, 2011). As they travel all the layers the current becomes weak to be recorded so it has to be amplified, and digitalized and then stored in the memory.

Brain Waves:

Brain waves are defined as some oscillating electrical voltages in the brain. The general amplitude of brain wave is around a millionth of a volt. Different regions of brain emit different frequencies and we need to put those electrodes in that manner. Majorly there are 5 types of brain waves as described in table -1, and figure 1 representing the waves.

Table 1.

Different Brain waves and their characteristics

Frequency Band	Frequency (Hz)	Brain State
Gamma (γ)	>35 Hz	Concentration
Beta (β)	12 – 35 Hz	Anxiety Dominant, Active, External Attention, Relaxed
Alpha (α)	8 – 12 Hz	Very Relaxed
Theta (θ)	4 – 8 Hz	Deeply Relaxed, inward focused
Delta (δ)	0.5 – 4 Hz	Sleep

Source: Created by the Author, based on information

Figure 1.

Different Brain waves and their characteristics