What is the recommended input impedance in relation to CMRR?

The recommended input impedance in relation to Common Mode Rejection Ratio (CMRR) is very high. High input impedance is essential in electroencephalography (EEG) to minimize the loading effect on the electrodes and to ensure that the electrical signals from the brain are not significantly altered by the measurement system.

When input impedance is high, it allows the EEG system to detect very weak brain signals without drawing significant current from the electrodes. This capability improves the system's ability to maintain the integrity of the brain's electrical activity and ensures accurate measurements. A very high input impedance also contributes to a better CMRR, as it allows the EEG system to reject common-mode signals, like electrical noise from surrounding environments, while still being sensitive to the differential signals from the brain.

Considering these factors, the option of being less than CMRR does not accurately represent the relationship since input impedance needs to be significantly higher than the common mode signals rejected by the CMRR for effective and accurate EEG recordings.