Low Resolution EEG Tomography (LORETA) Neurofeedback & Quantitative EEG Assessment
The field that deals with mapping activity of the brains is called “neuroimaging”. Neuroimaging falls into two categories: structural imaging and functional imaging. In structural imaging, researchers look at the structure or anatomy of the brain. A change in the brain structure by e.g. a brain tumor or damage from a stroke may all come to light with structural imaging. Functional imaging is concerned with mapping the activity of the brain. For example, when we sleep, brain areas work differently compared to the awake state. So the structure remains unaltered but the brain activity changes.
Functional imaging allows researchers to study information processing in the brain. If we want to know how the brain works and reacts in a given situation, we must follow this approach.
PET, fMRI and the EEG
Today there are three image processing techniques dominating the field of functional imaging. These are positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and electro encephalogram (EEG). PET and fMRI have in common that measurement is based on subtle changes in the oxygen content of the blood. The reasoning behind this is that active brain tissue consumes more oxygen than idling brain tissue. So the more blood rich in oxygen arrives in one area, the more active that area will be. PET and fMRI scanners are quite expensive devices, however they are able to map deep layered brain tissue. When it comes to measuring deep brain areas, fMRI goes a step beyond PET, measuring brain activity with much higher precision in terms of location. This property is also called source localization.
Another functional imaging technology is qEEG (quantitative EEG) or the Brain Map. This is markedly less expensive than the PET or fMRI. Another big difference with PET and fMRI is that in EEG the electrical activity of the brain is measured directly instead of looking at the amount of oxygen in the blood from which brain activity can be derived. The huge advantage of this direct measurement is brain activity can be picked up within a very short time delay. Within the context of neurofeedback, this is an important finding. In terms of our knowledge of neurophysiology we know that the faster the brain gets feedback on what it does, the more effective the brain learns from that feedback. This is where feedback and Operant Conditioning come into the picture of EEG Neurofeedback.
LORETA qEEG ANALYSIS
Since the 1990s, there has been much research done to remedy the deficiency with respect to source localization. This research has led to the emergence of a new method called LORETA (low resolution brain electromagnetic tomography). LORETA is actually a set of mathematical algorithms that calculate three-dimensional location of a certain brain activity. In fact LORETA estimates the location of activity with a reasonably high degree of accuracy. Measuring deep brain structures based on electrodes that reside on the scalp is like finding the epicenter of an earthquake based on measurements at the surface. The calculations are based on LORETA conventional EEG.
NEUROFEEBACK WITH LORETA
In classical neurofeedback one uses two or three sensors to measure and train those brain areas just below the skull. However LORETA neurofeedback uses 19 different sensors. This seems like a lot of extra work; by using multiple sensors one can get a measure and train deeper areas far below the skull surface. For example, one of those deeper brain structures is called the limbic system. The limbic system is a collection of brain areas that deal with memory and emotional regulation. Since many mental problems have their origin in a disturbance within the limbic system LORETA neurofeedback offers enormous potential for treatment. Another example is Post Traumatic Stress Disorder. In this case the amygdala, located in the limbic system, is often involved. This is a brain region that affects emotional regulation and is often impacted by PTSD. We are able to directly train this area with better symptom resolution than traditional neurotherapy.
What we are able to achieve with traditional neurofeedback, we are able to achieve in a substantially more rapid manner changes in terms of neural regulation and symptom resolution. However, LORETA is not recommended as a first line of approach in young children unless there are significant problems associated with diagnoses such as Traumatic Brain Injury, PTSD, OCD, Learning Disabilities and Autism. We prefer to start with traditional training for those 2-4 years of age and surface Z score for those five and above. LORETA neurofeedback is based on treatment of the Brodmann areas of the brain. The 19 locations of the brain that can be trained with surface neurofeedback correspond to specific deep sites within the brain known as Brodmann areas.
Brodmann areas were originally defined and num- bered by the German anatomist Korbinian Brodmann based on the cytoarchitectural organization of neurons he observed in the cerebral cortex. Brodmann published his maps of cortical areas in 1909. From the beginning it was assumed that different structures served different functions, the areas have been discussed, debated, refined, and renamed for nearly a century and remains the most widely known and frequently cited cytoarchitectural organization of the human cortex. Many of the areas Brodmann defined were based solely on their neuronal organization and have since been correlated to diverse cortical functions.
When we perform LORETA neurofeedback it is important to take information from the qEEG and correlate this with neural networks within the brain that are linked to clinical symptoms (Thatcher). We then go directly to the source of the problem, deep within the brain. Please remember, although the name states “electric” there is no electric applied. It is similar to traditional neurofeedback but the analysis is different and much more complex. There are many applications for the use of LORETA.
Z SCORE NEUROFEEDBACK
LORETA neurofeedback training involves the use of Z score in order to analyze and treat. This means that one obtains positive feedback as long as the targeted brain activity remains within a certain range of the standard (e.g. the norm) activity. These norms are derived from extensive normative EEG databases. If the brain activity falls outside this range, the client receives negative feedback. In training we have games that are used in order to obtain this feedback.. This approach is highly technical and there are limited providers of this technology in this country. At this point in time, LORETA is the most advanced form of EEG Neurofeedback available.
Because of its ability to measure deeper brain areas LORETA neurofeedback is a more effective treatment method than classical neurofeedback and even surface Z score neurofeedback. LORETA uses the “inverse problem”. In LORETA, mathematical formulas reconstruct the source of deep brain activity based on surface measurements. The inverse problem states that, given a surface measurement, there are always multiple solutions (sources) possible. So more than one type of brain activity can lead to the same measurement the relationship between source and surface measurement is not one to one.