EEG Band Power values: Units, Amplitudes, and Meaning

The ASIC_EEG_POWER_INT values are indications of relative amplitudes of the individual EEG bands.

Typically, power spectrum band powers would be reported in units such as Volts-squared per Hz (V^2/Hz), but since our values have undergone a number of complicated transforms and rescale operations from the original voltage measurements, there is no longer a simple linear correlation to units of Volts. Hence, we do not try to label them with any conventional unit. You can think of them as ASIC_EEG_POWER units, if you must.

The reason we say they are only meaningful compared to each other and to themselves is primarily due to the fact they have their own units as described above. It would not necessarily be meaningful nor correct to directly compare them to, say, values output by another EEG system. In their currently output form, they are useful as an indication of whether each particular band is increasing or decreasing over time, and how strong each band is relative to the other bands.

Because the EEG wave bands represent a power spectrum, their values will vary exponentially, meaning the lower-frequency bands (such as delta and theta) will be exponentially larger values than the higher-frequency bands (alpha and beta). For analysis purposes, note the comparison warning above. For display purposes, if you would like to remove the exponential gaps between the bands to make them appear closer to each other, you could display the logarithm of each value, instead of the exponential values themselves.