The ERD_ERS value is in the range from [100 %, +100%] and describes the spectral change of activity at sampling time t relative to
the activity during the baseline epoch. A value of +100% means that activity is twice as high as during the baseline epoch.
The baseline epoch can be defined in the "Epoch" tab of the paradigm editor. If no baseline epoch was defined,
the ERD/ERS display is not available.