Brain stem auditory evoked fields in response to clicks

Abstract

Magnetoencephalographic correlates of brain stem auditory evoked potentials (BAEP) have been identified by applying the model of a current dipole with invariant location and orientation (fixed dipole) to data recorded with a 37-channel first-order gradiometer system. In all three subjects studied, the dominating wave of the recorded brain stem auditory evoked field (BAEF) coincided exactly with wave V in the contralateral BAEP (maximal field amplitude of the order of 2-3 fT). In one subject, also a wave preceding wave V was observed, which was associated with basically the same spatial pattern as wave V itself, but had an opposite polarity. The study suggests that the supplementary information provided by BAEF measurements could be decisive for a better understanding of human auditory evoked brain stem activity.

Sources of auditory brainstem responses revisited: Contribution by magnetoencephalography

“…However, the field patterns indicated, as reported earlier [Lü tkenhö ner et al, 2000;Scherg and von Cramon, 1985], that a single equivalent current dipole may not be a satisfactory source for the later ABR/mABR waves as there probably are several simultaneously active generator sites in the neural structures. Furthermore, the different conductivities of the brain tissue (0.3 S/m employed here) and the cerebrospinal fluid [1.8 S/m; Baumann et al, 1997] in the fourth ventricle, close to the observed wave V source region, may contribute to the localization error.…”

“…A set of virtual channels, sensing source currents without directional specificity, derived from a priori anatomical information about the assumed source location have successfully been used to recover the time course of a deep source [Tesche, 1996]. In addition, MEG measurements of the auditory brainstem responses have been demonstrated [Erné and Hoke, 1990;Erné et al, 1987;Iramina and Ueno, 1995;Lü tkenhö ner et al, 2000].…”

Bioelectric and Biomagnetic Localization of Deep Sources in the Brain: A Model Study

“…In the electric case the ECD is described by the Gabor-Nelson equations [8], [9] resulting from Eq. (2). The moment of the ECD is given by the electric dipole moments, i. e., (6) The location of the ECD is described by a System of five equations obtained from the electric quadrupole moments.…”

Influence of a preceding auditory stimulus on evoked potential of the succeeding stimulus

“…The results showed that the amplitude of the P50 component of the AEP of succeeding stimuli was much smaller than that of the preceding stimuli when lSI was less than 500 ms. Liitkenhoner [13,14] studied the auditory evoked magnetic fields (AEF) with magnetoencephalography (MEG) in normal subjects when receiving paired sound stimulus. Judd [5] studied the specific sensory gating deficits in schizophrenic patients.…”