Quantitative EEG brain mapping

Quantitative Electroencephalogram (qEEG) is a means of measuring the brain's electrical activity to assess function and performance. Whereas some forms of brain measurement (like MRIs) look at the actual physical structure of the brain (like computer hardware), the EEG is more an indicator of how the brain is performing (like computer software).

All communication between brain cells is an electro/chemical process that can be measured at the scalp as a minute electrical discharge. This electrical activity is measured in microvolts (millionths of a volt) and therefore requires amplification to be effectively measured. It is truly amazing to think that our energy efficient brains function on a fraction of a volt of power!

Traditionally EEG measurement has been almost exclusively used to identify seizure activity in the brain. Sometimes background epileptic patterns can be seen, but if a seizure occurs at the time of measurement it often looks like a large spike of fast wave activity followed immediately by a large amplitude slow wave. This is the well know spike and wave pattern that may repeat several times during the course of an epileptic seizure.

In more recent times quantitative EEG has emerged as a means of measuring (or quantifying) a variety of variables in the brain that enables the clinician to map out the entire functioning of the brain's electrical system.

One means of quantifying the EEG has involved the development of normative databases that allow an individual's EEG to be compared to the group average for their age and gender to identify variance from the norm. There are a number of such databases that have been developed that usually involve identifying a group of individuals who have been screened for any psychological or neurological problems and have been been deemed to be "normal".

EEG brainwave activity is then measured under various conditions ... usually eyes closed and eyes open, but some databases also include tasks such as reading or mathematics to see how the brain performs under a challenge. The collective EEG data is then collated and EEG norms are established for age and gender. An individual EEG can then be compared to the norm and a treatment plan devised based on measured variations from the norm at a variety of cortical locations.

While database comparison can be very helpful, some would argue "who wants to be normal or average anyway?" One can only imagine where people like Albert Einstein or Leonardo da Vinci would have sat within the normative database!

Another form of quantitative EEG assessment, therefore, is to compare the individual brain not to the group average, but to itself. This method is based on research into the localisation of various functions within the brain. For example, it is well established that the left side of the brain in which language interpretation and production occurs is generally more active than the right. Similarly, the brain should be in a relaxed state dominated by alpha brainwave activity when eyes are closed, but the alpha amplitude should decrease by approximately 50% when eyes are open.

By measuring EEG brainwave activity at a number of cortical locations under a variety of conditions it is possible to identify whether a brain is functioning optimally and whether any possible discrepencies can reasonably explain areas of dysfunction that the client wants to change. For example, if the client's brain is more active on the right than the left and they also struggle with anxiety or anger management, then it would be reasonable to expect that their overactive right hemisphere is contributing to the problem. Neurofeedback protocols could then be established that encourage the brain to decrease the amplitude of fast beta waves on the right side of the brain, resulting in a more relaxed nervous system.

At Neuro Development Services we routinely use the latter method, but access database comparison when necessary. Both methods of quantitative EEG assessment can be very helpful in providing an understanding of brain function and designing effective treatment plans.