A system comprising: a memory configured to store electrical signal levels; and processing circuitry configured to: determine, for one or more electrodes of a plurality of electrodes, respective time-varying measurements of current source densities (CSDs) based on the electrical signal levels; aggregate, for the one or more electrodes of the plurality electrodes, the respective time-varying measurements of the CSDs to generate respective average level values for the one or more electrodes of the plurality of electrodes; determine, for one or more electrodes of the plurality of electrodes, respective phase-magnitude representations of the time-varying measurements of the CSDs, wherein the respective phase-magnitude representations are indicative of respective magnitudes and phases of a particular frequency component of respective time-varying measurements of the CSDs, wherein the particular frequency component is a frequency component having a largest transform coefficient in a time-varying measurement of a CSD having a largest average level value; and generate information indicative of the respective average level values and respective phase-magnitude representations. a memory configured to store electrical signal levels; and processing circuitry configured to: determine, for one or more electrodes of a plurality of electrodes, respective time-varying measurements of current source densities (CSDs) based on the electrical signal levels; aggregate, for the one or more electrodes of the plurality electrodes, the respective time-varying measurements of the CSDs to generate respective average level values for the one or more electrodes of the plurality of electrodes; determine, for one or more electrodes of the plurality of electrodes, respective phase-magnitude representations of the time-varying measurements of the CSDs, wherein the respective phase-magnitude representations are indicative of respective magnitudes and phases of a particular frequency component of respective time-varying measurements of the CSDs, wherein the particular frequency component is a frequency component having a largest transform coefficient in a time-varying measurement of a CSD having a largest average level value; and generate information indicative of the respective average level values and respective phase-magnitude representations. determine, for one or more electrodes of a plurality of electrodes, respective time-varying measurements of current source densities (CSDs) based on the electrical signal levels; aggregate, for the one or more electrodes of the plurality electrodes, the respective time-varying measurements of the CSDs to generate respective average level values for the one or more electrodes of the plurality of electrodes; determine, for one or more electrodes of the plurality of electrodes, respective phase-magnitude representations of the time-varying measurements of the CSDs, wherein the respective phase-magnitude representations are indicative of respective magnitudes and phases of a particular frequency component of respective time-varying measurements of the CSDs, wherein the particular frequency component is a frequency component having a largest transform coefficient in a time-varying measurement of a CSD having a largest average level value; and generate information indicative of the respective average level values and respective phase-magnitude representations. <EOS>