The rise of the citizen scientist is being spurred on by new access to research-grade hardware at publically affordable prices. In this article, we specifically discuss various electroencephalography (EEG) hardware systems that are now commercially available and their impact on research within and outside of academic institutions. Although previous-generation research-grade EEG recording devices were expensive and not portable, new EEG headsets are becoming more affordable and portable. This article discusses various research studies that have used newer, accessible EEG devices to cover a variety of research topics that range from a focus on medical disorders to cognition to thought-controlled video games and neurally-responsive art.
What Is Electroencephalography?
Electroencephalography (EEG) was first introduced in 1924 and revolutionized neuroscience by enabling a non-invasive recording of both human and animal brains during awake, conscious activity. EEG measures electrical activity from the surface of the brain using electrodes placed on the scalp (Figure 1). The electrical activity recorded by the EEG scalp electrodes is caused by neurons generating action potentials. An action potential refers to a single electrical firing of an individual neuron, the small impulse that forms the basis of all communication between neurons. It takes from thousands to millions of concurrent action potentials across the brain to create an electrical signal large enough for an EEG system to detect it. The ability to record neural signals by electrodes placed noninvasively on the scalp has been remarkably useful for learning about brain abnormalities as well as healthy neural functioning .
A Brief History of EEG
Around 1780, an Italian scientist named Luigi Galvani conducted a revolutionary experiment in which he connected the nerves of a dead frog to an electrical wire. In doing so, Galvani became the first scientist to explore the effect of electrical stimulation on animal muscle tissue. Galvani found that electrical stimulation caused the frog’s leg to move. This discovery paved the way to electroencephalography. After Galvani, neuroscientists continued to expand their understanding of electricity in the brain and peripheral nervous systems of animals. Although many scientists were critical in the invention of the EEG, a German man named Hans Berger is considered to be the father of modern electroencephalography. Building on past experiments, Berger used electrodes, an electrometer, and a galvanometer to create the first EEG. By placing electrodes onto the scalp and needles into the scalp, he recorded human brain waves. He was the first to do so and he called the waves he recorded Alpha and Beta, the first two letters of the Greek alphabet. Following this landmark experiment, Grey Walter created a toposcope which used a greater density of electrodes and cathode-ray tubes to obtain higher quality signals. Since then, EEG technology has advanced considerably and can now be used as a medical tool in addition to other diverse applications .
Modern EEG Recording Hardware: Research Grade
While Dr. Walter’s 1957 EEG boasted 37 electrodes, modern research-grade EEG systems use up to 256 electrode channels. To ensure consistency between experiments and to target specific regions of the brain, these electrodes are carefully positioned on the scalp, often held in place using a geodesic head cap, a mesh, or a rigid grid. In some experiments, each electrode temporarily adheres directly to the scalp.
Neural signals are very small in magnitude after passing through the layers of protection around the brain, including the thick bone of the skull. As a result of this attenuation, quality EEG recording requires amplification, which has become an integral part of the EEG hardware. Moreover, the skull dampens not only the magnitude, but also the range of frequencies of neural signals that can be recorded. The higher frequency signals are the most dampened, or attenuated, by the skull. The quality of the EEG recordings is also dependent on the sampling rate of the EEG hardware. The sampling rate is how many times per second the data is collected. Increasing the sampling rate leads to more precise waveforms. Typical research-grade EEGs have sampling rates of about 128 Hz to 1000 Hz, or 1 kHz. The need for high-end amplifiers and recording hardware in some experimental protocols can cause research-grade EEG to be very expensive, with costs ranging from $1000 to $25,000 or more .
Modern EEG-Recording Hardware
Luckily, as technology has progressed, EEG systems have become both more powerful and less expensive. Now, with the addition of new and sophisticated mathematical tools, even just a few electrodes of EEG activity can be enough to drive basic brain-computer interfaces (BCI) and shed light on cognitive states like focus and relaxation. This has led to the rise of EEG systems that are both portable and affordable, delivering EEG systems that one can now buy commercially, at a local electronics store. These wireless, cheaper, and commercially-available EEG headsets are more accessible for research as well as personal use. The following section discusses various commercial EEG sets as well as their “citizen research applications.”
Mindwave: Mindwave was one of the earliest commercial wireless EEG headsets built by NeuroSky in 2010. It is an EEG that uses Bluetooth for communication to a device. The Mindwave headband is readily adjustable, making it easier to wear and size appropriately. It was built specifically to be used by developers who are building apps for health and entertainment. It comes with NeuroView and NeuroSkyLab software interfaces to allow for approachable and cost-effective ways to perform EEG research. This headband costs $99.95. Because of these tools, there are now multiple commercial applications that use MindWave available on sites such as Amazon .
ThinkGear: The ThinkGear ASIC Module EEG headset, also created by NeuroSky, focused on improving the physical EEG hardware technology. This headset has a powerful, fully integrated single-chip EEG sensor that uses printed circuit boards (PCBs), allowing for higher quality neural recordings. ThinkGear also has dry electrodes that better filter out the noise and electrical interference to increase sensitivity to brain electrical signals. Although high-quality sensors are used, this headset is still priced for mass production and commercial applications .
Emotiv: Emotiv was founded in 2011 and has built a wide variety of EEG headsets. A recent addition to Emotiv’s array of EEG headsets is the Emotiv EPOC X, a 14-channel wireless EEG headset that uses saline-soaked ‘wet’ electrodes. The design of this headband is unique because it has a rotating feature that allows the headband to be positioned at the top of the head or the rear of the head, enabling recording from frontal or occipital lobes of the brain. This feature is also useful because it allows for people who might need head support to use the headband. Additionally, Emotiv developed a 3D brain visualizer that uses spatial resolution and source localization techniques to depict the source of the recorded activity over the entire brain. A typical Emotiv headband costs $299.00 .
Muse: This Muse headband, created by Interaxon, measures electrical activity over the frontal lobe and muscles of the eyes and forehead. It was created to deliver biofeedback about brain activity to help users control emotions. This device has been used to measure electrical activity in participants' brains while playing a car driving game to decode distraction. The Muse headband has also been used to create neural-influenced art and virtual reality environment renderings and comes with dedicated app support for research and further commercial development. It costs $209.99 .
Myndlift: Released in early 2015, Myndlift is now a popular choice for neurofeedback studies. Myndlift uses the same physical technology as the Interaxon Muse headband, and it has the same EEG electrodes, headset, and software . Research projects using Myndlift include those studying attention deficit hyperactivity disorder (ADHD), post-traumatic stress disorder (PTSD), traumatic brain injury (TBI), and cognitive enhancement. In one study, nineteen participants diagnosed with ADHD engaged or did not engage with the mobile Myndlift neurofeedback system (intervention vs control group). Only the intervention group showed a significant increase in overall performance in a cognitive task and reduction in hyperactivity, supporting the idea that neural feedback devices like Myndlift technology may be effective in treating ADHD . Additional studies have demonstrated that the Myndlift neurofeedback system may be effective for treating other mental health disorders, as well.
Neurable: Neurable is a more recent headset that has 6 dry electrodes. It uses machine learning algorithms to perform high-quality signal processing, allowing for clearer signals with less noise. Despite the relatively fewer electrodes used, Neurable has greater than 90% correlation with wet EEG systems. Neurable is also readily accessible to developers and is compatible with most virtual reality headsets with eye-tracking software. The software tools Neurable has built can be integrated with Unity, C, and C++ environments for developers, used for 3D data visualization. It is compatible with other wearable sensing devices and devices that would allow for real-time streaming. One disadvantage of Neurable is that although it only has six electrodes, it is relatively bulky and large .
Other Research With Commercial EEG Headsets
With the rise of cheaper and more available headsets, there is a wide variety of fields that have potential commercial uses of EEG, whether it be at-home mental treatment, gaming studies, or even music recommendations based on one’s EEG brain waves. This section discusses several research studies that have employed commercial EEG headsets to explore such fields.
In 2012, two scientists, Lowerse and Hutchinson, used an Emotiv EEG headset to study spatial and temporal patterns in the brain during language processing. They discovered that specific linguistic and perceptual regions of the brain are involved in processing concepts and that these brain regions can be distinguished using commercially-available EEG .
In a 2015 research study, researchers used a Muse headband to identify signals during the experience of pain. The researchers developed a protocol that can be used at home to classify brain signals by different pain-related brain states in real-time. This could enable a brain-computer interface that administers pain medication proportional to pain level, reducing the risk of over-or under-dosing a patient. The accuracy of the system they developed also demonstrates that commercially available wireless EEG headsets can be used for highly accurate, real-time brain state classification .
Commercial EEG headsets have also been used to study addiction and multiple studies have demonstrated the effectiveness of neurofeedback from these headsets in treating addiction. Neurofeedback is where one uses a real-time display of one’s brain waves to learn to control internal brain processes.
In an early 2005 study, for example, fourteen alcoholic outpatients with depressive syndrome were treated using the Muse wireless headband and the Myndlift neurofeedback system to increase relaxation by gaining control of their low-frequency alpha and beta brain waves. Data collected after 21 months revealed a drastic reduction in scores from Beck’s depression inventory, indicating less severe depression, and lower scores in the Millon Clinical Multiaxial Inventory-1, indicating less drug abuse . In another study, 120 inpatient alcoholics were either given a form of Myndlift’s neurofeedback system with the Muse headband (experimental group) or not given treatment (control group). A year later, more people from the experimental group continued treatment and more people from the experimental group remained abstinent during and following the treatment. This demonstrates the impact of the Myndlift system and the commercially-available Muse EEG headband .
These EEG headsets have also been used in research on a variety of BCI systems in which brain signals are used to control an external device. For example, a ThinkGear headset was used to create a human-like robot that operates based on recorded brain signals [17}. The goal of this project was to create a device that could assist those who are disabled – a goal that has been accomplished using an expensive, research-grade EEG headset but had not been done with a wireless and relatively cheap EEG headset. The results of this study demonstrated that advanced technologies such as BCIs can be built with more accessible EEG headsets.
Other Neural Recording Modalities: Future Commercial Devices
New commercial ventures are working towards improving EEG and neural recording tools. For example, Neuralink is creating an invasive recording tool with a phenomenally high sampling rate, microelectrodes that can record from many single neurons at once, and a special USB cable that allows for full bandwidth streaming from the electrodes . This company has also built a neurosurgical robot for placing their tiny, small, and flexible electrode threads into the brain - currently of pigs, but the vision is to make these implants available to humans someday. Currently, the surgical robot has microscopic precision to prevent damage to vascular tissue of the brain and to target highly specific brain regions.
Another upcoming venture involves functional near-infrared spectroscopy (fNIRS). This non-invasive technology measures changing hemoglobin concentrations by measuring certain waves emitted by the brain to get a refined EEG signal. Recently there has been an almost exponential growth of research studies that use fNIRS for brain imaging. Also, they have a relatively low cost, are easy to make, and are adjustable for various purposes. This points to the idea that the fNIRS might soon be ready to be used in commercial settings .
Commercially available wireless EEG headsets have now been on the market for over 15 years and much progress has been made. Though none of them are perfect, each of the wireless EEG headsets discussed here has unique qualities that make them very useful. For example, while the ThinkGear module features high-quality EEG sensors, Emotiv has a distinctive setup for the design of the headband that makes it more accessible and allows for the EEG reading to give more information. While Myndlift offers an advanced neurofeedback system that has proved itself in various research studies, Mindwave has focused more on arming developers with an accessible programming environment and a suite of research tools to promote the development of novel commercial applications. To date, commercially available wireless headsets have revealed promising avenues for citizen research and rapid development of human self-interaction, as with neurofeedback. Undoubtedly, research in the coming years will further reduce the costs and improve the performance of these headsets.
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