Quantitative EEG Assessment
Quantitative EEG or Brain Mapping
Quantitative Electroencephalogram (qEEG) or Brain Mapping is a procedure that records electrical activity within the brain from 19 channels. This tool gives us the ability to view the dynamic changes taking place throughout the brain during processing tasks and assists in determining which areas of the brain are fully engaged and processing efficiently. The brain map provides a baseline to work from while we retrain the brain and regulate metabolic and physiological problems in the body.
The brain behaves like any other electrical system. Changes in membrane polarization, inhibitory and excitatory post-synaptic potentials, action potentials etc. create voltages that are conducted through the brain tissues. These electrical voltages enter the membranes surrounding the brain and continue up through the skull and appear at the scalp where they are measured as microvolts. This electrical activity occurs at several different frequencies.
These potentials are recorded by an electrode that is attached to the scalp with non-toxic conductive gel. The electrodes are fed into a sensitive amplifier. We record the EEG from many electrodes arranged in a particular pattern using a cap that is sized according to the circumference of the skull. The pattern we use is the international 10/20 standard for describing these positions. The 10-20 system is based on the relationship between the location of an electrode and the underlying area of cerebral cortex.
The “10-20 System” of Electrode Placement
Each point on the skull is linked with an electrode position. Each site has a letter (to identify the lobe) and a number or another letter to identify the hemisphere location. The letters F, T, C, P, and O stand for Frontal, Temporal, Central, Parietal and Occipital. (Note that there is no “central lobe”, but this is just used for identification purposes.) Even numbers (2,4,6,8) refer to the right hemisphere and odd numbers (1,3,5,7) refer to the left hemisphere. The z refers to an electrode placed on the midline.
Electrical activity is described by three characteristics; frequency, amplitude and intensity. Frequency is measured in Hertz (Hz); it is the number of times a wave repeats itself within a second. It can be compared to the frequencies that you tune into on your radio. If any of these frequencies are deficient, excessive, or difficult to access, our mental performance can suffer. Amplitude represents the power of electrical impulses generated by brain. Intensity, which is like the volume of brain wave activity, is measured in microvolts.
The raw EEG is usually described in terms of five frequency bands described below. Each of these has its distinct function and can be used to detect brain dysfunction.
Delta (0.1 to 3 Hz)
The lowest brain frequencies are Delta waves. These occur in deep sleep and in some abnormal processes that might be associated with a traumatic brain injury. They also are produced during experiences of “empathy states”. Delta waves are involved with our ability to integrate and let go. Delta activity reflects our unconscious mind. It is the dominant rhythm in infants up to one year of age and is present in stages 3 and 4 of sleep. It tends to be the highest in amplitude and is considered to be the slowest wave. We increase Delta waves in order to decrease our awareness of the physical world. We also access information in our unconscious mind through Delta. Peak performers decrease Delta waves when high focus and increased performance are required. However, most individuals diagnosed with Attention Deficit Disorder, naturally increase rather than decrease Delta activity when trying to focus. This inappropriate Delta response
often severely restricts their ability to focus and maintain attention. It is as if the brain is locked into a perpetual drowsy state. The effect of increasing Delta by training is to induce drowsiness, trance and deeply relaxed states. Another way to look at Delta is to imagine you are driving in a car and you shift into 1st gear – you are moving but not going to get anywhere very fast. Delta represents 1st gear.
Theta (4-8 Hz)
Theta activity is classed as “slow” activity. It is seen in connection with creativity, intuition, daydreaming, and fantasizing and is a repository for memories, emotions and sensations. Theta waves are strong during internal focus, meditation, prayer, and spiritual awareness. It reflects the state between wakefulness and sleep and relates to the subconscious. It is abnormal in adults when awake but is perfectly normal in young children. It is also normal during sleep. Theta is believed to reflect activity from the limbic system and hippocampal regions. When the theta rhythm appears to function normally, it mediates and/or promotes adaptive, complex behaviors such as learning and memory. If Theta is enhanced by training, it can induce a drifting, trance-like state. If suppressed, it can improve concentration and our ability to focus attention. In our car example, Theta would be considered 2nd gear. Not as slow as 1st gear (Delta) but still not very fast.
Alpha (8-12 Hz)
Alpha waves usually will peak around 10Hz. Good healthy Alpha production promotes mental resourcefulness, aids in the ability to mentally coordinate and enhances an overall sense of relaxation. In this state you can move quickly and efficiently to accomplish whatever task is at hand. When Alpha predominates, most people feel at ease and calm. Alpha appears to bridge the conscious to the subconscious. It is the major rhythm seen in normal relaxed adults. It is present during most of life especially beyond the thirteenth year when it dominates. We think that Alpha rhythms are derived from the white matter of the brain. The white matter can be considered the part of the brain that connects all parts with each other. Alpha occurs whenever a person is alert but not actively processing information. They are strongest over the occipital (back of the head) cortex and also over frontal cortex. Alpha has been linked to extroversion (introverts show less), creativity (creative subjects show Alpha when listening and coming to a solution for creative problems), and mental work. When our Alpha is within normal ranges we tend to also experience good moods, see the world truthfully, and have a sense of calmness. Alpha is one of the brain’s most important frequencies enabling us to learn and use information taught in the classroom and on the job. You can increase Alpha by closing your eyes or breathing deeply. You can decrease Alpha by thinking or calculating. Alpha training can produce relaxation and in conjunction with Theta training can create an increase in sensation, abstract thinking and self-control. In our car scenario, Alpha would represent neutral or idle. Alpha allows us to shift easily from one task to another.
Beta (above 12 Hz)
Beta activity is ‘fast’ activity and it reflects desynchronized active brain tissue. It is usually seen on both sides of the brain in symmetrical distribution and is most evident frontally. It may be absent or reduced in areas of cortical damage. It is generally regarded as a normal rhythm and is the dominant rhythm in those who are alert or anxious or who have their eyes open. It is the state that most of the brain is in when we have our eyes open and are listening and thinking. Beta is activated when we are problem solving, making judgments or decisions or processing information about the world around us.. The Beta band has a relatively large range and has been divided into sub ranges. Low Beta (12-15 Hz), formerly called “SMR” or Sensorimotor Rhythm, makes us feel relaxed, yet focused and integrated. Deficient low Beta can reflect “ADD” and a lack of focused attention. Conversely, increasing low Beta can produce relaxed focus and improved attentive abilities. Beta (15-18 Hz) is produced by thinking and awareness of self and our surroundings. It occurs with alertness but not agitation. Training can increase mental ability, focus, alertness and IQ. High Beta (above 18 Hz) is also related to alertness and mental activity, e.g. math, planning, but is also associated with agitation. Training in this frequency can induce alertness, but may also produce agitation. Beta represents overdrive or hyper-drive in our car scenario.
Gamma (above 36 Hz)
Gamma is the only frequency group found in every part of the brain. It is thought that the 40Hz Gamma brain activity consolidates various brain areas for simultaneous processing. A good memory and well-integrated thoughts are associated with well-regulated and efficient 40Hz activity, whereas a 40Hz deficiency creates learning disabilities. The effects of Gamma training are unknown.
What Does the qEEG Brain Map Look Like?
Colors are obtained on the maps which indicate levels of activity. They allow us to see in a graphical way how the brain receives and processes information and then executes responses. These colors are expressed in terms of Standard Deviations and percentages and are based on the data obtained from the qEEG. There is a great deal of other information that might additionally be useful to a Neurologist.
How to Read the Brain Map
At Neurobehavior Therapy a respected database (Neuroguide) is used to obtain a better view of how the brain is behaving and to determine if it is performing within normal limits. The database uses a mathematical technique that compares the EEGs of ‘normal’ brain functioning individuals with the client’s EEG during eyes open and eyes closed. A normative database allows for an objective measurement of the EEG and regions in the brain in order to develop an individualized training program.
Each Brain Map report includes extensive statistical tables of absolute power and relative power, power asymmetry and synchronization (coherence), and color-coded topographic brain maps. In addition, if there is a history of mild traumatic brain injury this can be measured in the eyes closed EEG recording. If there is a history of learning disabilities this can be measured in the eyes open recording.
This data is used to help identify normal and abnormal brain electrical activity. Selected EEG features from different brain regions quantify the organization within the brain to identify disturbances in brain processing. Brain processing problems often reveal themselves in the QEEG in one or more of the following brain wave categories:
Absolute Power – Absolute Power measurement assists in determining whether enough brainpower within a particular frequency range is present at each recording site.
Relative Power – The Relative Power measurement assists in determining whether a particular frequency is overpowering other vital brain frequencies.
Mean Frequency – Each frequency band is measured between specific ranges. The average frequency tells us whether or not that specific bandwidth is operating within normal ranges.
Ratios – Relationships are extremely important! Relationships between the various brain frequencies are compared to those individuals with normal brain functioning. Ratios lower or higher than normal are a sign of inefficiency in either the brain’s ability to process incoming information or in attending to and executing specific tasks.
Asymmetry – Asymmetry scores reveal to us whether the brain waves between the various parts of the brain are balanced. Excessive, localized activity may indicate an overtiring of brain cells. Insufficient activity may suggest brain cells are not firing sufficiently to maintain proper brain function.
Coherence – In order for us to understand the complexity of the world and to make and execute decisions, the different parts of the brain must share information. Coherence is one of the ways we measure how well the brain is able to perform this inner self-talk. Coherence gives us an indication of how efficiently our brain is working to connect and disconnect different parts of itself to accomplish a particular task.
Excessive Coherence tends to indicate two or more areas of the brain are “overly connected or locked together.” That is, the brain has become overly dependent on those centers and is not efficiently processing and executing information. This tends to result in poor day-to-day performance. Serious traumatic brain injury classically results in excessive Coherence. On the other hand, deficient Coherence is the EEG sign of a brain not able to efficiently connect cortical areas to perform specific tasks. Learning Disabilities may show excessive and/or deficient Coherence characteristics.
Phase – Many of the brain’s functions are timed events; the energy from one part of the brain should arrive at another area at just the right moment to perform a specific task. The qEEG measurement of this important factor is called Phase. Excessive Phase statistics mean the signals arrive too early and deficient Phase means the signals arrive too late. In either case, the brain is not able to do its job with peak efficiency.
How Do We Use the Maps?
The qEEG allows us to view the brain in an active, functional state so that we can literally “see” problems. Unlike other methods of “viewing” the brain, qEEG Brain Mapping allows us to see more than the physical structure of the brain. This is especially valuable for those sensitive to psychiatric illnesses, which are often characterized by disturbances of brain organization rather than brain structures.
When we are considering a set of symptoms from a brain processing point of view, the contribution of each brain wave dysfunction can often be quite revealing. For example, when we are considering focal slow waves (Delta or Theta waves) we generally will find them at the root of many learning difficulties. In those with Dyslexia, slow brain wave activity can be found in one or more key areas. These can include the occipital lobes at the back of the brain, where incoming visual information is received and processed; Wernicke’s area located in the left parietal lobe where the brain processes words for understanding; Broca’s area located in the left frontal lobe, where words are put together for expression. We also often find these slow waves in the sensorimotor area, where speech is converted from a feeling for verbalization of thoughts.
As another example – our brain uses its 8-13 cycles per second Alpha waves to idle itself; to rest areas not actively processing and acting on incoming sensory and motor information. While this idling is a normal and favorable phenomenon for the healthy brain, if Alpha wave activity becomes “locked” and inhibited, active participation of vital brain areas cannot occur with efficiency. The frontal lobes are the areas most commonly affected by excessive (flooding) and non-reactive (inhibited) Alpha waves. Our brain uses its frontal lobes to focus attention outside itself and to understand the complexities of the world. It is not unusual to find high amplitude, frontal Alpha in those failing academically and those having trouble meeting job demands.
Keep in mind that there is no one brain wave pattern seen in all of those with a specific disease, disorder, or inefficiency. In fact, the qEEG in those with Attention Deficit Disorder, for example, may show high amplitude Delta slow waves, excessive Theta activity, or a locked-in Alpha state in a variety of areas.
We also use the qEEG to identify and guide treatment for behavioral disorders such as depression. Asymmetry in Alpha and Beta brain activity is the brain’s most reliable signature for depression; a common side effect of Learning Disabilities. Those with depression may show high Alpha or Beta, excessive coherence problems, or poor communication between the left and right frontal lobes.
Brain problems can also arise due to physical trauma such as in a traumatic brain injury or TBI. In these cases, because the brain has a natural ability to adapt, a damaged brain will attempt to survive by releasing neuro-inhibitors to protect its limited resources. In doing so, it locks itself into a particular electro-chemical pattern in order to not make matters worse. When this happens, we find ourselves losing flexibility in our ability to attend, which reduces our ability to adapt to varying circumstances. Over time, our personality generally becomes rigid and we begin to feel that there are no solutions to our problems. This is often the root of an overwhelming sense of helplessness and hopelessness and tends to drives us to mood extremes, such as depression, anger and even uncontrollable rage. The Brain Map can help the clinician identify these specific changes and deficits early to prevent long-term problems.
Unfortunately, many brain processing related disorders present with similar symptoms.
Without the qEEG, it is almost impossible to differentiate ‘what is what’. It is the qEEG that helps sort out what is causing the symptoms. With the qEEG Brain Map, treatment using EEG Neurofeedback is precise, making the process more direct and efficient. Neurotherapy that relies on “canned” protocols such as placement of one or two electrodes on regions of the brain based on clinical symptoms is not evidenced based and is often ineffective. The field has progressed considerably over the years and the use of the qEEG is considered to be the “gold standard” for providing EEG Neurofeedback.