The hallmark of Quantitative EEG is the comparison of the artifacted data to a normative database matched for age. Our primary databases are BrainDx, Neurorep, and Neuroguide. BrainDx was created by neuroscientists affiliated with NYU Medical Center. It is based on the original database created by Prof Roy John. EEG magnitude spectra are viewed for eyes closed and open raw and artifacts data sets. This enables the precise determination of the posterior dominant rhythm and its suppression upon eye opening. At the PDR frequency the magnitude or amplitude at every sensory location can be measured and compared. Artifacting is done manually through the NREP software suite. Traditionally, we stay away from automatic artifacting procedures and continued with this approach at present. There will then be a review of the raw EEG with automated seizure and spike analysis performed as necessary.
As was the case with NxLink in the past, frequency band based maps are generated that are compared to the normative database. This includes delta, theta, alpha, beta, beta2 and total frequency maps. Database analyses are produced for absolute power, relative power, asymmetry and coherence values. BrainDx comparisons can be made for all individuals at age of 6 and older for eyes closed. This database can now be used for adults for eyes open as well, and pediatric norms for the eyes open condition are in development. One of the most unique components of this database is the use of narrow band spectra which compares to the database in 0.3 hz. increments. Once a frequency is selected (for exceeding a z-score cutoff), exact z-score values are calculated at every electrode location. Brain regions with the greatest deviations from the norm can be mapped and their frequency distributions determined at a very specific and precise degree.
Once frequency of interests have been selected, sLoreta analysis may be conducted to determine maximum z-scores, frequencies and source locations. In BrainDx analyses can be done separately for slice (typical) or volumetric sloreta (seen to the left). sLoreta is a solution to the EEG inverse problem that mathematically proposes to determine the source (or sources) of predetermined EEG activity. Volumetric sLoreta shows a distribution of sources with a maximum value determined as well
We also utilize the Neuroguide QEEG database for all clients to analyze their eyes open data stream. This provides similar information including aspects of absolute and relative power for frequency and single hz. maps. This information may be imaged for non-norm referenced data as well as complete z-score analyses as well. These can certainly be compared to the BrainDx images for similarities and differences.
We do not utilize or interpret coherence analyses from either BrainDx or Neuroguide for the reasons discussed here. At this point in time, we utilize NeuroRep multivariate coherence analyses to understand these complex synchronization patterns.
The NeuroRep compare program is also utilized to objectively measure changes when comparing to a previous EEG. This very clearly helps to assess changes that occur as a result of treatment or any other intervention over a period of time. This includes reliability estimates across the two EEG’s to determine validity and stability over time. Changes in coherence, magnitude, absolute and relative power are imaged and subjected to analysis.
Independent Component Analysis (ICA) is an EEG signal processing method used to isolate independent sources which are linearly mixed in several sensors. Due to the length between the skull and brain and their varied resistences, EEG data obtained at any given point on the scalp also includes the activity produced across a significant area of the brain. Utilizing ICA with EEG data distinguishes the issues of source identification from that of source localization. Independent Components Analysis can separate out artifact from your EEG data as they are independent of each other, and presents a specific pattern of coherence which can be used to generate a personalized protocol for your clients.
All of these data, images and their interpretation are presented and reviewed during the online video consultation.