Normal FMAER - effect of reference electrode. The waveforms for 20 channels of a 4 Hz FMAER study are shown to the left as recorded from a neuro-typical 7 year old control subject. Electrode designations appear below each channel’s waveform which is one second in duration. An amplitude scale is shown to the right in microvolts (uV). All data are derived from the same subject. Topographic voltage maps are shown to the right at the same scale as the waveforms, with blue representing negative and red positive activity. For each map the nose is shown above, occiput below, with left ear to the left. The map is formed at the maximum negativity of electrode CZ at the waveform midpoint. The upper combined waveform and topographic map (A) show the display as it appears when the data are referenced to linked ears, as is commonly used. The lower display set (B) shows the data when the common average reference is employed, as recommended here. Note the difference in both amplitude and spatial locations of the FMAER on both the waveform and the mapping imposed by the difference in referencing.
Duffy et al. BMC Neurology 2013 13:12 doi:10.1186/1471-2377-13-12