Issue link: https://resources.mouser.com/i/1449105
Molex 2022 11 Figure 1: A woman undergoing non-invasive electroencephalography (EEG). (Yakobchuk Viacheslav/Shutterstock.com)troencephalography-695951221). BCI & EEG The human brain produces oscillating electronic voltages. The typical value of these voltages is minimal, measured in units on the order of millionths of volts. The most common way to collect and analyze these brain-wave voltages is through an electroencephalogram (EEG). An EEG is an electrophysiological monitoring method to record electrical activity on the scalp. It captures signals directly related to the brain waves happening directly under the skull (Figure 1). BCI via an EEG can be unidirectional (one-way) or bidirectional (two-way). Bidirectional allows information to flow both ways, thus opening the brain to feedback and future adjustments. EEGs can be invasive, semi- invasive, or non-invasive. Invasive EEGs involve directly locating and connecting devices into the human brain. Semi-invasive EEGs can be placed between the brain and the skull. Non-invasive is generally done by a cap placed on the skull with various electrodes. EEGs provide temporal resolution of @ 0.05 seconds and spatial resolutions on the order of 10mm. Other techniques, besides the electrical technique employed by EEGs, can be used to gather data. These techniques can employ magnetic, metabolic, or other forms. Brain waves are classified into one of five general categories based upon their frequency (Table 1). Medical researchers break these into bands because each band represents a distinct way a brain operates in performing its functions. For example, critical activities such as memory and recollection happen especially, but not exclusively, in the theta band. Researchers use these bands to analyze what might be going on if it appears signals are too little, too great, or an optimal amount. An EEG acquires the brainwave signals and digitizes them. They are then signal-processed where features can be extracted and translation algorithms perform classifications. They also can be printed out or recorded for future analysis. Signal outputs can be utilized to form device commands to provide instructions related to motor control, locomotion/movement, and environmental conditions or stimuli. BCI helps allow disabled people to have more control of their external environments. Table 1: The five general categories of brain wave bands. Each frequency range is a nominal value and not necessarily absolute. (Source: Author) Band Frequency (Hz) Delta 0.5-3 Theta 3-8 Alpha 8-12 Beta 12-38 Gamma 38-42