An Electroencephalogram, commonly known as an EEG, is a non-invasive test that measures the electrical activity of the brain. The brain’s billions of cells communicate through tiny electrical impulses, and an EEG records these signals. These electrical signals appear as wavy lines, or brain waves, on a computer screen, reflecting the ongoing activity within the brain. Understanding these brain wave patterns can offer insights into various brain states and functions.
Understanding EEG Basics
An EEG operates by placing small, flat metal discs called electrodes onto the scalp. These electrodes detect the subtle electrical charges generated by brain cells, amplifying them so they can be recorded and displayed. The entire procedure is painless and takes approximately 30 to 60 minutes.
Brain waves are categorized by their frequency, measured in Hertz (Hz), and each type is associated with different states of consciousness or activity. Delta waves, with frequencies up to 4 Hz, are the slowest and are observed during deep sleep. Theta waves, ranging from 4-8 Hz, are linked to drowsiness, light sleep, and deep relaxation, and are also present during meditation or daydreaming.
Alpha waves, at 8-13 Hz, are characteristic of a relaxed yet alert state, often seen when someone is calm or daydreaming. Beta waves, at 13-30 Hz, dominate during active, focused thinking, problem-solving, and alert states. Finally, gamma waves, with frequencies above 30 Hz, are associated with higher-order cognitive processing and mental activities like studying.
EEG and ADHD: Brainwave Patterns
Individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) exhibit brainwave patterns that differ from those of neurotypical individuals. Research consistently finds an increase in theta wave activity, particularly in the frontal regions of the brain. This phenomenon, sometimes called “theta excess,” is thought to reflect a state of underarousal in the prefrontal cortex, a brain area important for executive functions like attention and impulse control.
This heightened theta activity is accompanied by a decrease in beta wave activity. The ratio of theta to beta waves, known as the theta/beta ratio, is higher in individuals with ADHD compared to those without the condition. An elevated theta/beta ratio has been hypothesized to suggest difficulties with attention or impulsivity, reflecting a dysregulation in attentional processes.
Beyond the theta/beta ratio, other brainwave differences have been observed in ADHD. Some studies indicate altered alpha wave patterns, relating to sensory processing and filtering distractions. Variations in EEG patterns are also noted among different ADHD subtypes, and some research suggests differences in gamma wave activity, linked to cognitive processing.
The Role of EEG in ADHD Assessment
Quantitative EEG (QEEG) involves the computerized analysis of raw EEG data to compare an individual’s brainwave patterns against a normative database. While QEEG can highlight differences in brain function, its role in diagnosing ADHD is a subject of ongoing discussion within the scientific community.
The Food and Drug Administration (FDA) approved an EEG-based marker, the theta/beta ratio, in 2013 as part of the Neuropsychiatric EEG-Based Assessment Aid for ADHD (NEBA) system. While some studies suggest that using NEBA in conjunction with traditional clinical assessments can increase diagnostic accuracy, it is not intended as a standalone diagnostic tool.
Major medical and psychiatric organizations do not recommend routine EEG testing as a primary diagnostic tool for ADHD. The diagnosis of ADHD relies on a comprehensive clinical evaluation, which includes:
Established diagnostic criteria
Behavioral assessments
Rating scales
Interviews with the patient and those familiar with their behavior
Limitations of EEG in ADHD diagnosis include variability in findings, a lack of widespread standardization, and similar EEG abnormalities can be found in other neurological and psychiatric conditions.
EEG-Guided Neurofeedback for ADHD
Beyond its assessment role, EEG technology is used in a therapeutic application called neurofeedback. Neurofeedback aims to help individuals learn to self-regulate their brainwave patterns to improve ADHD symptoms. This approach is rooted in the concept of neuroplasticity, the brain’s ability to change and adapt.
During a neurofeedback session, electrodes are placed on the scalp to monitor brain activity in real-time. This brain activity is then translated into visual or auditory feedback, often in the form of a video game or sounds. For example, a person might learn to increase beta waves, associated with focus, or decrease theta waves, linked to drowsiness, by receiving positive feedback when their brain produces the desired patterns.
The goal of neurofeedback is to train the brain to produce more optimal brainwave patterns, thereby improving symptoms such as inattention, impulsivity, and hyperactivity. Research continues, and neurofeedback is considered a complementary intervention leveraging the brain’s capacity for self-regulation to enhance attention and self-control.