A special case would be the LM ERP waveforms at the very same sites that were used to compute the linked-mastoids reference (i.e., TP9 and TP10; rectangular insets in Fig. 2). By removing the algebraic mean from either site, the resulting reference ERPs become inverted waveforms of each other (symmetric ERPs with respect to the baseline). However, ERP deflections that are common to both sites with any other reference are completely removed from TP9 and TP10, similar to the flat line seen at the Nose for NR data. Notably, this reference effect is less obvious for the LM data because it is masked by the residual waveforms remaining at these sites.
