Neurofeedback is a form of biofeedback that uses electrical potentials in the brain to reinforce desired brain states through operant conditioning. This process is non-invasive and typically collects brain activity data using electroencephalography (EEG). Several neurofeedback protocols exist, with potential additional benefit from use of quantitative electroencephalography (QEEG) or functional magnetic resonance imaging (fMRI) to localize and personalize treatment. [1] [2] Related technologies include functional near-infrared spectroscopy-mediated (fNIRS) neurofeedback, hemoencephalography biofeedback (HEG), and fMRI biofeedback.
Placebo-controlled trials have often found the control group to show the same level of improvement as the group receiving actual neurofeedback treatment, which suggests these improvements may be caused by secondary effects instead. [3] [4] [5] Neurofeedback has been shown to trigger positive behavioral outcomes, such as relieving symptoms related to psychiatric disorders or improving specific cognitive functions in healthy participants. These positive behavioral outcomes rely on brain plasticity mechanisms and the ability of subjects to learn throughout life. [6]
In 1898, Edward Thorndike formulated the law of effect. In his work, he theorized that behavior is shaped by satisfying or discomforting consequences. This set the foundation for operant conditioning.[ citation needed ]
In 1924, the German psychiatrist Hans Berger connected several electrodes to a patient's scalp and detected a small current by using a ballistic galvanometer. In his subsequent studies, Berger analyzed EEGs qualitatively, but in 1932, G. Dietsch applied Fourier analysis to seven EEG records and later became the first researcher to apply quantitative EEG (QEEG).
In 1950, Neal E. Miller of Yale University was able to train mice to regulate their heartbeat frequency. Later on, he continued his work with humans, training them through auditory feedback. [7]
The first study to demonstrate neurofeedback was reported by Joe Kamiya in 1962. [8] [9] Kamiya's experiment had two parts: In the first part, a subject was asked to keep their eyes closed, and when a tone sounded, to say whether they were experiencing alpha waves. Initially, the subject would guess correctly about fifty percent of the time, but some subjects would eventually develop the ability to better distinguish between states. [10]
M. Barry Sterman trained cats to modify their EEG patterns to exhibit more of the so-called sensorimotor rhythm (SMR). He published this research in 1967. Sterman subsequently discovered that the SMR-trained cats were much more resistant to epileptic seizures after exposure to the convulsant chemical monomethylhydrazine than non-trained cats. [11] In 1971, he reported similar improvements with an epileptic patient whose seizures could be controlled through SMR training. [12] Joel Lubar contributed to the research of EEG biofeedback, starting with epilepsy [13] and later with hyperactivity and ADHD. [5] Ming-Yang Cheng was instrumental in advancing research on EEG neurofeedback, specifically targeting enhancements in SMR power among skilled golfers. [14]
In 2010, a study provided some evidence of neuroplastic changes occurring after brainwave training. In this study, half an hour of voluntary control of brain rhythms led to a lasting shift in cortical excitability and intracortical function. [15] The authors observed that the cortical response to transcranial magnetic stimulation (TMS) was significantly enhanced after neurofeedback, persisted for at least twenty minutes, and was correlated with an EEG time-course indicative of activity-dependent plasticity [15]
The term neurofeedback is not legally protected. There are various approaches that give feedback about neuronal activity, and as such are referred to as "neurofeedback" by their respective operators. Distinctions can be made on several levels. The first takes into account which technology is being used (EEG, [16] [17] [18] [19] [20] [14] fMRI, [21] [22] [23] [24] fNIRS, [25] HEG). Nonetheless, further distinctions are crucial even within the realm of EEG neurofeedback, as different methodologies of analysis can be chosen, some of which are backed up by a higher number of peer-reviewed studies, whereas for others, scientific literature is scarce, and explanatory models are entirely missing.
Despite these differences, a common denominator can be found in the requirement of providing feedback. Usually, feedback is provided by auditory or visual input. While original feedback was provided by sounding tones according to neurological activity, many new ways have been found. It is possible to listen to music or podcasts where the volume is controlled as feedback, for example. Often, visual feedback is used in the form of animations on a TV screen. Visual feedback can also be provided in combination with videos and films, or even during reading tasks where the brightness of the screen represents the direct feedback. Simple games can also be used, where the game itself is controlled by the brain activity. Recent developments have tried to incorporate virtual reality (VR), and controllers can already be used for more involved engagement with the feedback.
Amplitude training, or frequency band training (used synonymously), is the method with the largest body of scientific literature; it also represents the original method of EEG neurofeedback. [8] [12] [5] The EEG signal is analyzed with respect to its frequency spectrum, split into the common frequency bands used in EEG neuroscience (delta, theta, alpha, beta, gamma). The activity involves training the amplitude of a certain frequency band on a defined location on the scalp to higher or lower values.
Depending on the training goal (for example, increasing attention and focus, [26] [27] reaching a calm state, [28] reducing epileptic seizures, [12] [29] [30] etc.), the electrodes have to be placed in different positions. Additionally, the trained frequency bands and the training directions (to higher or lower amplitudes) might vary according to the training goal.
Thus, EEG wave components that are expected to be beneficial to the training goal are rewarded with positive feedback when appearing and/or increasing in amplitude. Frequency band amplitudes that are expected to be hindering are trained downwards by reinforcement through the feedback.
As an example, considering ADHD, this would result in training low-beta or mid-beta frequencies in the central-to-frontal lobe to increase in amplitude, while simultaneously trying to reduce theta and high-beta amplitudes in the same region of the brain. [31] [32] [33]
In the sports domain, SMR training has garnered attention, with a substantial body of research suggesting that enhancing it could improve performance. [34] This improvement is particularly evident after multiple training sessions [14] designed to enhance motor skills critical for precise movements. Such precision is required in various sports activities, [35] including golf putting, soccer free kicks, and basketball free throws.
For SCP (slow cortical potentials) training, one trains the DC voltage component of the EEG signal. The application of this type of EEG neurofeedback training was mostly endorsed by research done by Niels Birbaumer and his group. The most common symptom base for SCP training is ADHD, whereas SCPs also find their application in brain-computer interfaces. [36]
Normal EEG signals are restricted to the surface of the scalp. Using a high number of electrodes (19 or more), the source of certain electrical events can be localized. Similar to a tomography that renders a 3D image out of many 2D images, the many EEG channels are used to create LORETA images that represent in 3D the electrical activity distribution within the brain. The LORETA method can be used in combination with MRI to merge structural and functional activities. It is able to provide even better temporal resolution than PET or fMRI. For the application with live neurofeedback, however, 19-channel neurofeedback and LORETA has limited scientific evidence, and until now, shows no benefit over traditional 1- or 2-channel neurofeedback. [37]
There is ongoing discussion about the effect size of neurofeedback in the scientific literature. As neurofeedback is explained mostly based on the model of operant conditioning, [38] the sensitivity of the feedback (the difficulty to receive a reward) also plays a role. It has been shown that the desired conditioning can be reversed if threshold values are set too low. [39] Other publications have not found any effect of neurofeedback, apart from placebo, when using automatic thresholds that update every thirty seconds in order to maintain a constant success rate of 80%. [40] [41]
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterised by executive dysfunction occasioning symptoms of inattention, hyperactivity, impulsivity and emotional dysregulation that are excessive and pervasive, impairing in multiple contexts, and developmentally-inappropriate.
Biofeedback is the technique of gaining greater awareness of many physiological functions of one's own body by using electronic or other instruments, and with a goal of being able to manipulate the body's systems at will. Humans conduct biofeedback naturally all the time, at varied levels of consciousness and intentionality. Biofeedback and the biofeedback loop can also be thought of as self-regulation. Some of the processes that can be controlled include brainwaves, muscle tone, skin conductance, heart rate and pain perception.
Delta waves are high amplitude neural oscillations with a frequency between 0.5 and 4 hertz. Delta waves, like other brain waves, can be recorded with electroencephalography (EEG) and are usually associated with the deep stage 3 of NREM sleep, also known as slow-wave sleep (SWS), and aid in characterizing the depth of sleep. Suppression of delta waves leads to inability of body rejuvenation, brain revitalization and poor sleep.
An event-related potential (ERP) is the measured brain response that is the direct result of a specific sensory, cognitive, or motor event. More formally, it is any stereotyped electrophysiological response to a stimulus. The study of the brain in this way provides a noninvasive means of evaluating brain functioning.
A brain–computer interface (BCI), sometimes called a brain–machine interface (BMI), is a direct communication link between the brain's electrical activity and an external device, most commonly a computer or robotic limb. BCIs are often directed at researching, mapping, assisting, augmenting, or repairing human cognitive or sensory-motor functions. They are often conceptualized as a human–machine interface that skips the intermediary of moving body parts (hands...), although they also raise the possibility of erasing the distinction between brain and machine. BCI implementations range from non-invasive and partially invasive to invasive, based on how physically close electrodes are to brain tissue.
Neurotechnology encompasses any method or electronic device which interfaces with the nervous system to monitor or modulate neural activity.
A gamma wave or gamma rhythm is a pattern of neural oscillation in humans with a frequency between 30 and 100 Hz, the 40 Hz point being of particular interest. Gamma rhythms are correlated with large-scale brain network activity and cognitive phenomena such as working memory, attention, and perceptual grouping, and can be increased in amplitude via meditation or neurostimulation. Altered gamma activity has been observed in many mood and cognitive disorders such as Alzheimer's disease, epilepsy, and schizophrenia.
Hemoencephalography (HEG) is a neurofeedback technique in the field of neurotherapy. Neurofeedback, a specific form of biofeedback, is based on the idea that human beings can consciously alter their brain function through training sessions in which they attempt to change the signal generated by their brain and measured via a neurological feedback mechanism. On completion of the process, participants increase cerebral blood flow to a specified region of the brain, consequently increasing brain activity and performance on tasks involving the specific region of the brain.
The sensorimotor rhythm (SMR) is a brain wave. It is an oscillatory idle rhythm of synchronized electric brain activity. It appears in spindles in recordings of EEG, MEG, and ECoG over the sensorimotor cortex. For most individuals, the frequency of the SMR is in the range of 7 to 11 Hz.
Alpha waves, or the alpha rhythm, are neural oscillations in the frequency range of 8–12 Hz likely originating from the synchronous and coherent electrical activity of thalamic pacemaker cells in humans. Historically, they are also called "Berger's waves" after Hans Berger, who first described them when he invented the EEG in 1924.
Brainwave entrainment, also referred to as brainwave synchronization or neural entrainment, refers to the observation that brainwaves will naturally synchronize to the rhythm of periodic external stimuli, such as flickering lights, speech, music, or tactile stimuli.
The sensorimotor mu rhythm, also known as mu wave, comb or wicket rhythms or arciform rhythms, are synchronized patterns of electrical activity involving large numbers of neurons, probably of the pyramidal type, in the part of the brain that controls voluntary movement. These patterns as measured by electroencephalography (EEG), magnetoencephalography (MEG), or electrocorticography (ECoG), repeat at a frequency of 7.5–12.5 Hz, and are most prominent when the body is physically at rest. Unlike the alpha wave, which occurs at a similar frequency over the resting visual cortex at the back of the scalp, the mu rhythm is found over the motor cortex, in a band approximately from ear to ear. People suppress mu rhythms when they perform motor actions or, with practice, when they visualize performing motor actions. This suppression is called desynchronization of the wave because EEG wave forms are caused by large numbers of neurons firing in synchrony. The mu rhythm is even suppressed when one observes another person performing a motor action or an abstract motion with biological characteristics. Researchers such as V. S. Ramachandran and colleagues have suggested that this is a sign that the mirror neuron system is involved in mu rhythm suppression, although others disagree.
Attention deficit hyperactivity disorder management options are evidence-based practices with established treatment efficacy for ADHD. Approaches that have been evaluated in the management of ADHD symptoms include FDA-approved pharmacologic treatment and other pharmaceutical agents, psychological or behavioral approaches, combined pharmacological and behavioral approaches, cognitive training, neurofeedback, neurostimulation, physical exercise, nutrition and supplements, integrative medicine, parent support, and school interventions. Based on two 2024 systematic reviews of the literature, FDA-approved medications and to a lesser extent psychosocial interventions have been shown to improve core ADHD symptoms compared to control groups.
The Applied Neuroscience Society of Australasia (ANSA) is a non-profit professional organization for applied neuroscience in Australia, with members in Australia, New Zealand and Asia.
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex and allocortex. It is typically non-invasive, with the EEG electrodes placed along the scalp using the International 10–20 system, or variations of it. Electrocorticography, involving surgical placement of electrodes, is sometimes called "intracranial EEG". Clinical interpretation of EEG recordings is most often performed by visual inspection of the tracing or quantitative EEG analysis.
Thomas Hice Budzynski was an American psychologist and a pioneer in the field of biofeedback, inventing one of the first electromyographic biofeedback training systems in the mid-1960s. In the early 1970s, he developed the Twilight Learner in collaboration with John Picchiottino. The Twilight Learner was one of the first neurotherapy systems.
Error-related negativity (ERN), sometimes referred to as the Ne, is a component of an event-related potential (ERP). ERPs are electrical activity in the brain as measured through electroencephalography (EEG) and time-locked to an external event or a response. A robust ERN component is observed after errors are committed during various choice tasks, even when the participant is not explicitly aware of making the error; however, in the case of unconscious errors the ERN is reduced. An ERN is also observed when non-human primates commit errors.
Bioelectromagnetic medicine deals with the phenomenon of resonance signaling and discusses how specific frequencies modulate cellular function to restore or maintain health. Such electromagnetic (EM) signals are then called medical information, which are used in health informatics.
NeuroIntegration Therapy (NIT) is a non-invasive combination therapy that integrates quantitative electroencephalography (qEEG or QEEG) brain mapping with additional therapies such as neurofeedback, vibroacoustic therapy, pulsed electromagnetic field therapy (PEMFT, or PEMF therapy) and photic stimulation (light therapy.)
Matthew D. Sacchet is a neuroscientist, Associate Professor of Psychiatry, and Director of the Meditation Research Program at Harvard Medical School and Massachusetts General Hospital. His research focuses on advancing the science of meditation and includes studies of brain structure and function using multimodal neuroimaging, in addition to clinical trials, neuromodulation, and computational approaches. He is notable for his work at the intersection of meditation, neuroscience, and mental illness. His work has been cited over 6,000 times and covered by major media outlets including CBS, NBC, NPR, Time, Vox, and The Wall Street Journal. In 2017 Forbes Magazine selected Sacchet for the “30 Under 30”.