SOURCE ESTIMATION OF AUDITORY BRAIN-STEM EVOKED-POTENTIALS - COMPARISON OF 3CLT AND DIPOLE LOCALIZATION

The generators of auditory brainstem evoked potentials (ABEPs) are gen erally agreed to be located between the auditory nerve and upper pens. Thus, they are all located within a few cm from the center of the hea d. Three-channel Lissajous' trajectory (3CLT) provides the amplitude a nd orientation of a centrally located equivalent dipole of surface rec orded activity. Volume conductor theory predicts decreased spatial res olution of source estimation the deeper the source. In this study we c ompared source estimates obtained with 3CLT, using three orthogonal di fferential channels, with those obtained with two other source estimat ion methods: i) setting the generators at their known anatomical coord inates and calculating orientation and magnitude of the source (dipole localization method-DLM); ii) estimation of all source parameters, in cluding the number of sources by wavelet-type decomposition, without a ssumptions on the location of the sources (multiple source estimate-MS E). 3CLT, DLM and MSE all converged on magnitudes and orientations tha t were not significantly different from each other, and locations that were within a few cm of each other. In conclusion, although 3CLT can only estimate a single, centrally located equivalent dipole, in the sp ecific case of ABEPs, it provides the same information available from the more demanding source estimate methods. In addition to the conside rable saving in recording channels, 3CLT is reference-independent and thus avoids ambiguities resulting from the choice of reference.