Brain Interfaces: Invasion of the Non-Invasive

  • Wearables that turn your intentions into actions.
  • Computers can predict our preferences directly from our brains.
  • Pacemakers for the brain can zap away negative thoughts.

These are just a few of the headlines about brain interfaces. With a market size sitting at about $2 billion and a projected growth rate of over 15%, brain interfaces are not only here but trickling into our lives. This is exponentially the case for non-invasive brain interfaces. These are brain interfaces that are not surgically implanted but applied to or near the surface of the skin. They can take many forms such as a wearable, a headset or an immersive space. The longevity and the supporting science of the established modalities give it legs to stand on as an emerging technology. Today, the range of brain interface applications is wide-ranging from military uses to education to market analytics to entertainment. For this installment, we will focus on modalities and use cases for medical and wellness applications. Perhaps the best way to slice the pie is to address modalities and then current and developing use cases.


Think of modalities as technology categories for the delivery of stimulation and/or the sensing of nerve signals from the human body. This is an area where acronyms are of high prevalence like EEG, MEG, tDCS, rTMS, and more. For the average person like me, the acronyms make it easier in conversation. The modalities are best defined by our partners at Neuromodec. With their help, we will explore the modalities of non-invasive brain interfaces.

Electroencephalogram — EEG

BitBrain EEG headset

EEG has a long history in neurotech scientific discovery. This modality was discovered in the late 1920s and migrated into clinical use during the next two decades. EEG is a technology that detects brain activity. Through the use of small sensing electrodes attached to or placed on the scalp, they pick up electrical activity or impulses. It has been mainly used as a diagnostic tool in medical applications like monitoring seizure activity in people living with epilepsy or understanding sleep patterns. More recently, EEG has been used for brain-computer or machine interfaces and for the sensing aspect of adaptive stimulation therapies like spinal cord stimulation or deep brain stimulation. The traction of this technology shows in the number of commercial entities. We are tracking over 70 products that are either available for sale or near market launch using some form of EEG.

Magnetoencephalography — MEG

A related modality to EEG is the MEG. As the title implies the difference is MEG measures the magnetic fields produced within the brain’s own electrical activity. It is not typically provided in a wearable cap like EEG rather it is a large machine used in radiology clinics. MEG is most commonly used in seizure detection for people living with epilepsy.

Cranial Electrotherapy Stimulation — CES

This stimulation therapy takes the form of a small hand-held device that delivers low level electrical pulses to the brain through sponge electrodes that are placed on either side of the head. The electrical pulses are created by a generator that controls the amplitude and frequency of the pulses. CES was first introduced in the early 1970s but later took hold of the market in the mid-2010s. Mental Health America, a community-based non-profit organization advocating for those with mental illness, suggests clinical applications for a variety of brain conditions like ADHD, insomnia, anxiety, PTSD, depression, addiction, and more.

Transcranial Direct Current Stimulation — tDCS

Flow Neuroscience tDCS device

Much like the CES device, the tDCS device is a portable, hand-held device that delivers low level stimulation pulses to the scalp. It also has a control unit that generates the pulses. That is where the similarities end. tDCS is delivered through electrodes placed on either side of the scalp with one electrode providing the positive current (anode) and the other providing a negative current (cathode). The stimulation then crosses the brain and the stimulation is typically at a fixed level. There are some devices that have regulatory approval for depression, sleep or anxiety. Today, there is a wide array of clinical exploration for the use of tDCS in other areas of mental health such as schizophrenia or addiction as well as other areas of physical health like chronic pain and epilepsy. tDCS is also being applied as a combination therapy with training including physical rehabilitation, memory retention, and athletic training. As a wellness device for mindfulness. There are plenty of DYI kits to build your own device but a word of caution for buyer beware of unregulated stimulation devices to the brain.

Transcranial Alternating Current Stimulation — tACS

Much like its sister, the tDCS device, the tACS modality delivers low levels of electrical current to the brain in a similar fashion. The one difference is the form of the stimulation. For tACS the stimulation is delivered in an oscillating waveform at a specified frequency. The therapy is designed to enhance the brain’s natural rhythms. This modality can also be used as a wellness device outside the purview of the medical regulatory bodies. tACS is under clinical investigation for a variety of brain conditions such as depression, cognition, and motor performance.

Transcranial Magnetic Stimulation — TMS

This modality delivers electrical pulses like those previously described. The difference is how the pulses are generated. The delivery of stimulation is through a magnetic coil that is typically held over an identified area of the head. Magnetic stimulation was first discovered in the late 1800 but it really took hold for clinical use in 1985 when it was used by Barker and colleagues in an application to the motor cortex of the brain. TMS has many alternative forms such as Magnetic Seizure Therapy (MST) or Low-Field Magnetic Stimulation (LFMS) but the more popular alternative is Repetitive Transcranial Magnetic Stimulation or rTMS. This is when the pulses are delivered in a very quick fashion, one after the other or in a repeated pattern. Clinically, this modality has been used to treat depression, OCD and chronic pain and is also being explored for rehabilitation and epilepsy.

High Frequency Focused Ultrasound — FFU

Admittedly, this is not an exclusive modality within brain interfaces. It is, however, an emerging treatment for a variety of conditions of the brain. Traditional ultrasound is widely used as an imaging tool for internal soft tissue-like organs. Combine this imaging ability with high-frequency energy to target deep tissues by sending multiple intersecting beams and that is focused ultrasound. This emerging technology is a non-invasive modality for the treatment of obsessive-compulsive and biopolar disorders. It is also being investigated for autoimmune and inflammatory conditions. The Focused Ultrasound Foundation offers a wealth of information.

This list of modalities can’t possibly be exhaustive. There are other non-invasive brain interfaces that are in development like functional near-infrared spectroscopy (fNIRS), controllable pulse transcranial magnetic stimulation (cTMS), and transcranial static magnetic field stimulation (tSMS). This is a growing area of non-invasive neurotech and it is still in the early stages of widespread adoption.

Use Cases

Modalities are the tools to use but the use cases depict how those tools are used. At Neurotech Network, we typically focus on the conditions that the technologies treat. For this wide area of non-invasive brain interfaces, how the technology is used can have implications on a variety of conditions. Here is a highlight of the most common use cases for non-invasive brain interfaces.

Brain State Analysis

EEG may be the longest standing brain interface modality clinically, but brain analysis is probably the most seasoned of the brain interface use cases. In diagnostics, this technology is applied to understanding the depth of a depressive state, to strengthen new memory formation, to monitor anesthesia levels or to evaluate the quality of sleep. Brain state analyzers are devices used to detect mental states such as consciousness, drowsiness, or emotional distress. The use of EEG has expanded to improve the diagnosis of conditions of the brain and mental health such as Alzheimer’s disease, dementia and depression. They have influenced the ability to properly diagnose or assess conditions, such as epilepsy or brain injury. They also help improve the efficiency of care such as targeted pre-surgical planning and guiding treatment plans for psychological conditions.

Brain Computer or Brain Machine Interfaces — BCI/BMI

This category has attracted the public’s attention. Unlike Brain State Analysis, this is a few frontiers in brain interfaces. BCI/BMI take signals from the brain and convert them to interact with an external source for a particular action. That external source may be a computer or environmental control (BCI) or a mechanical or electrical object (BMI) such as a robotic arm or a stimulating electrode. Using technology to effectively capture neural activity in the brain has catapulted the development of assistive technology applications such as allowing a person with advanced ALS to communicate using a synthesizer. An example of a BMI case is the development of closed-loop systems that can sense action potentials in the brain and then use those signals to activate stimulating electrodes. For instance, a sensing electrode captures signals in the motor cortex of the brain to move a prosthetic limb, and the limb moves. In addition, information from sensors in the prosthetic limb is routed back to the sensory cortex to feel that same limb move. This can be key for amputees using prosthetic limbs and for neural prosthetic applications to move paralyzed limbs.


The area of therapeutics points to the use cases to deliver treatment to the brain for a condition. Most of the use cases in this category apply to mental health and brain disorders. TMS can be used to treat severe depression or obsessive-compulsive disorder. tACS can be used to also treat depression as well as anxiety, insomnia, and even headache conditions. The application of therapeutics is the topic of much of the clinical investigation. Scientists are studying the use of non-invasive brain stimulation in a wide range of conditions that have origins in the brain like Alzheimer’s and Parkinson’s diseases, ALS, addiction, or aphasia.

Cognition & Wellness

Training the brain has been a theme in the wellness arena and active aging. Stimulating brain interfaces have been used to help boost working memory or prepare the brain for learning a new task or information. This is still early in the establishment of scientific evidence but the ability to augment our cognitive state is an appealing proposition for the likes of aspiring athletes or cramming college students. Brain interfaces have also been used to calm the mind into a relaxing or mindfulness state. This use case is not only for the average person’s wellness but can have a meaningful impact on those living with post-traumatic stress or anxiety disorders.


This is an exciting area of research for the application of electrical stimulation and brain signals. Physical rehabilitation has traditionally focused on the mechanics of the body. There is a growing body of scientific evidence to support the need to simultaneously rehabilitate the body and the brain. One example is cortical stimulation applications for traumatic brain injuries and stroke survivors. Here the stimulation is applied to the damaged sections of the brain to excite neural activity to ‘retrain’ the brain neurons in a phenomenon known as neural plasticity. The brain is stimulated to become more engaged in physical activity. This has the potential to change the way we rehabilitate the body after damage to the brain. Brain stimulation can also have the potential to enhance the brain-body connection for paralyzing conditions like multiple sclerosis and spinal cord injury as well as for more common surgical procedures like hip and knee replacements.

These are just some of the use cases for non-invasive brain interfaces. There are more use cases in the pipeline of development and even more are in the ideation stage. With over 70 commercial entities (that we are tracking) in this field, there are surely more use cases to come as technology improves and we evolve with it.

Now that we have explored the implanted and non-invasive aspects of brain interfaces, our next part in this series will feature meeting the people. We will highlight some of the early adopters of brain interfaces to gain their perspectives.

More information about neurotech devices for various neurological conditions and other network resources may be found on the Neurotech Network website. The entire series can be found on Medium.