A simple method for the removal of mains interference from pre-recorded electrophysiological data

MOTIVATION A common problem with electrophysiological recording is the contamination of the signal of interest with interference generated at mains frequency. Standard filtering techniques are often inappropriate because the signal of interest has components spectrally close to the mains frequency. RESULTS A digital subtraction method is described for removing mains frequency interference from pre-recorded data. The data are first digitized with a sample rate that is some direct multiple of mains frequency. Next a 20 ms (for UK mains frequency) data set is constructed containing the average interference pattern. This is subtracted from each 20 ms window of the raw data. Finally, the mean value of the interference is added back to the raw data to restore the DC component. AVAILABILITY A Windows program which implements the method for the EGAA data acquisition system (R.C.Electronics, Santa Barbara, CA) is available from the author. CONTACT [email protected]