• Anthony Sosa

Deep-dive: How Does Neurofeedback Work?

Updated: Apr 25, 2021

To best understand how neurofeedback (NFB) works, it's important to understand three major components: EEG history and science basics, brain energy dynamics, and conditional feedback learning. Let's get started!



How EEG Works


In Part One, I will provide a brief history of the electroencephalogram (EEG), followed by an explanation of this technology.



History Lesson: The Electroencephalogram and Human Brain


First, let's look at a quick history recap of this technology. Research in EEG began with the discovery of bioelectricity in 1786. The Italian anatomy Professor, Luigi Galvani, observed how the electrical impulse in frogs would cause a twitch in the peripheral nerves and flex the muscles. Galvani was instrumental for biological science by showing how electricity is a force that controls our bodies. Later was a German physiologist Emil du Bois-Reymond (1818-1896). Bois-Reymond used his knowledge of the electrical properties in cells to pioneer our present-day understanding of action potentials, an action potential being the way our brain communicates based on how brain cells or neurons fire and signal to other neurons. Both Galvani and Bois-Reymond were pivotal in showing the world that the properties of electricity govern our bodies and brains.


The innovation of EEG was advanced further by a German neuropsychiatrist named Hans Berger (1873-1941). Hans Berger was a firm believer in psychic phenomena, such as telepathy, based on a near-fatal accident in his youth. This accident motivated the first record of the human brain. During the 1920s, after experiments using different galvanometers, such as placing electrodes on the scalp and using radio equipment to amplify the signal, he was able to detect electrical activity using needle-shaped epidural electrodes on the surface of a human skull. The studies by Dr. Berger confirmed that brain electrical activity does not require wires to be injected into the cerebral cortex to record electrical brain activity.


In 1929, Hans Berger introduced the term "electroencephalogram" in his published paper, "On the Electroencephalogram of Man," where he described the terms "alpha waves" and "beta waves." The name "Berger rhythm" was given to describe slower brain waves (alpha) in healthy persons at rest with their eyes closed. He's referred to as the "Father of Human EEG," He posited that fluctuations in the EEG might be related to human cognitive activity. His contributions, along with others, prompted future investigations and discoveries in neurophysiology and neuroscience.




What Does An EEG Measure?


Electroencephalogram (EEG) is an electrophysiological process that measures changes in the electrical activity of the brain. EEG uses sensors in the form of metal disks called electrodes placed on your scalp. The electrodes detect and record the electrical activity produced in your brain. The sensors detect your cerebral cortex's electrical activity, the thin layer that covers the outmost portion of your brain. Because of the advancement of EEG technology from analog to digital, the collected EEG signals are amplified and digitized and sent to a computer to interact with our neurofeedback program.


The greatest advantage and most central element of EEG are its excellent time resolution. An EEG has a high time/temporal resolution where an fMRI has an exceptional spatial resolution. An EEG can, in real-time, measure the relative strengths and positions of fluctuating electrical activity in different regions of the brain. It's like taking hundreds to thousands of snapshots of electrical activity changes within a single second.


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Figure 1. Showing the difference in how the two technologies EEG and fMRI obtain data about brain function.



What's the difference between an EEG and an fMRI?


In contrast, an fMRI uses magnetic fields to measure blood flow changes within different regions of the brain. The amount of blood flow each area receives is an indicator of which parts of the brain are most active. So fMRI provides accurate information about the location of brain activity, giving fMRI its renowned spatial resolution in imaging the brain. Although an EEG does not have nearly the same spatial resolution, it does measure the location and real-time electrical reactions of the brain at the speed of milliseconds.


The EEG is an excellent tool because of its technological capabilities to measure and record the precise time course of brain activity that correlates with cognitive and emotional processing underlying our behavior.



Voltage and Frequency of an EEG


The change in the electrical brain activity EEG measures is called voltage, measured in volts (V). Since the EEG signals are weak means that the voltage measures in microvolts (μV). One microvolt equals one-millionth of a volt or 0.000001 volts. Another way to say this is that 1μV=10-6 V. Voltage is also the electrical unit of potential difference, which has the same symbol. Potential difference is the measure of electrical potential energy. Potential difference refers to the difference in electrical potential (V) between two points or locations.


The electrical signals from the brain need amplification because EEG signals typically have small amplitude and low frequency. Meaning, EEG signals are fragile because of the bioelectrical signs of the human body. EEG low-frequency range is approximately between 0.5-50 Hertz (Hz). The electrical activity usually ranges from -100 to 100 (μV).


In your brain, changes in voltage (V) come from the ionic current within and between brain cells called neurons.


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Figure 2. The communication between neurons as neurotransmission. Incoming information is received at the dendrites. The outgoing information travels along the axon, where it interacts with the chemical medium of neurotransmitters before flowing at the chemical synapses to the receiving neuron. At the synapses, electrical signals are converted into biochemical signals to cross the gap from sending neurons to receiving neurons.



What is brain frequency?


The EEG measures various frequencies of your brain. It is essential to understand what is frequency. An algorithm, called Fast Fourier Transform (FFT), takes the raw EEG signals to be digitized as distinct waves with different frequencies. Frequency measures in cycles per second. One cycle per second equals one Hertz (Hz). In our case, frequency measures the changing speed of electrical oscillations (cycles) every second. These oscillating frequencies represent waves when shown on a screen. These waves represent your electrical brain activity in the form of brainwaves. Frequency ranges categorize brainwaves into four main types: Delta (0.5-4 Hz), Theta (4-8 Hz), Alpha (8-13 Hz), Beta (13-40 Hz).


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Figure 3. Graph of frequency (Hz) vs. time (s) and the four main frequency ranges.

What's essential for NFB is that these brain frequency ranges or bands have been found according to decades of research to be associated with specific brain-behavior functions. However, it's even more important to remember that there is no one-to-one linear correspondence between a particular frequency band and function of the brain.



Quantitative EEG (qEEG) and Neuro Mapping


What enhances our Clear Mind System neurofeedback is the Neuro Mapping feature. This feature refers to the brain map we create, representing a visual of patterned activity inside your brain. Because of the personally customized Neuro Map ability to highlight problem areas in the brain helps us to readily identify irregular or potentially dysfunction brainwaves relating to unwanted behavior or neurological disorders.


We create a map of your brain from using the qEEG brain cap using the 10-20 method of electrode placement. From your brain map and your personal account, we determine the best fit of qEEG driven protocols to help stimulate the desired brain frequencies.



What is qEEG?


A quantitative electroencephalogram (qEEG) combines EEG brain tests with data from other brain monitoring techniques and statistics from other individuals in the same gender and age range. This method is more effective because machine learning, qEEG records your brainwaves like a traditional EEG and then compares your brainwaves with similar individuals that do not have brain dysfunction.


The qEEG process creates your brain map through quantitative comparison. This allows us to offer highly customized neuro-maps that are uniquely tailored to our client's needs.


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