common mode rejection
Also written as: CMR
An amplifier characteristic that suppresses electrical signals common to both recording electrodes, thereby reducing environmental noise and artifact in neurodiagnostic recordings.
Full Definition
Common mode rejection is a fundamental principle in neurodiagnostic amplifier design that enables the suppression of unwanted electrical signals that appear simultaneously at both recording electrodes. This technical feature is crucial for eliminating environmental interference such as 60 Hz electrical noise, distant muscle activity, and other sources of artifact that would otherwise contaminate neurophysiological recordings. The common mode rejection ratio (CMRR) quantifies an amplifier's ability to reject these common signals while preserving the differential signal of interest. High-quality neurodiagnostic equipment typically achieves CMRR values exceeding 100 dB. Understanding this principle is essential for troubleshooting recording problems and optimizing signal quality in EEG, EMG, and evoked potential studies.
Usage
Usage note: Use lowercase unless at beginning of sentence; CMR acceptable as abbreviation
In Context
- "Poor common mode rejection resulted in significant 60 Hz contamination throughout the EEG recording." — Technical troubleshooting report
- "The amplifier's excellent common mode rejection eliminated most environmental artifacts from the EMG study." — Equipment performance note