Quantitative EEG and Event-Related Potentials

An electroencephalogram (EEG) is a recording from the surface of the scalp of the electrical activity produced by the brain.  This electrical activity includes self-regulatory, sensory, and cognitive processes.



Quantitative EEG (QEEG) uses computerized digital signal analysis to enhance the analysis of standard EEG.  This approach uses techniques such as Fourier analysis and wavelet analysis to quantitatively investigate frequency-based information in the EEG.

Certain frequency-based information has been shown to be reliable measures of brain function.  One such measure, Peak Alpha, is the specific frequency within the Alpha band (8-12Hz) where the highest relative amplitude occurs.  A higher frequency Peak Alpha is related to faster cognitive processing.


Peak Alpha PNG


An Event-Related Potential (ERP) is a subset of the EEG and which is specifically the brain’s responses to a sequence of external stimuli (auditory, visual, or tactile).

ERPs are extracted from the brain’s background electrical activity by recording the EEGs during several stimulus-response repetitions.  The EEG waveforms from each repetition are then time-locked to the stimulus and averaged.  The portion of the EEG which is not time-locked to the stimulus averages to zero.  What is left after averaging is the ERP, the part of the EEG time-locked to the stimulus.

By proper selection of the stimulus, sequence, timing, etc., often called an ERP paradigm, various cognitive domains can be targeted for investigation.

Due to the high precision of ERP recording (milliseconds in the time domain and microvolts in the amplitude domain), many aspects of fundamental sensory and cognitive processing can be evaluated in detail.

ERPs are used in basic cognitive research, as diagnostic biomarkers of neurological disorders, and as measures of drug effect in therapeutic trials.


While numerous QEEG/ERP studies have been successfully performed in research settings around the world, these studies have generally lacked the diagnostic reliability necessary to be clinically useful for most physicians.  This is primarily due to the inherent difficulty in implementing research-oriented equipment on a scale large enough to obtain the high accuracy and repeatability rates needed for clinical use.  Furthermore, the complex research-oriented hardware and methods are not practical enough to be used in real-world clinical settings.

The COGNISION™ System was designed from the outset to overcome these limitations.  The system is designed to be easy and practical enough to use in a physician’s office, while also being able to support the large-scale data collection requirements of the most demanding research applications.  Additionally, the extremely difficult task of analyzing the QEEG/ERP data is automatically accomplished with Neuronetrix’s proprietary pattern recognition software, reCOGNISION™.

The COGNISION™ System is a highly integrated, internet enabled, cognitive assessment system designed to perform validated QEEG and ERP tests in normal office settings.  The COGNISION™ Headset is battery-powered and wireless to be patient- and user-friendly.  The COGNISION™ Software System has many advanced features to facilitate automated testing and analysis even in large, multicenter clinical trials.