KLT analysis of brain potential maps during pain

The effect of pain on event related potentials was analyzed with spatial Karhunen-Loeve Transforms (KLT) of maps from 54-lead EEG recordings. The recordings were obtained using an auditory oddball paradigm, during pain and no-pain conditions. Group eigenfunctions were calculated from the mismatch negativity (MMN) responses of twelve subjects. The individual data for pain and no-pain conditions, respectively, were fitted with these group eigenfunctions across the conditions. In seven of the twelve subjects, the resulting fitting error was larger when pain eigenfunctions were fitted to control data rather than to pain data. This suggests that spatial features of the potential maps might be used as a means for differentiating between pain and no-pain conditions.