02362nas a2200169   4500008004100000022001400041245010400055210006900159260001200228300001200240490000700252520183600259653001202095100002102107700001702128856004702145       1982                        eng d  a0013-469400aScalp distribution of human auditory evoked potentials. I. Evaluation of reference electrode sites.0 aScalp distribution of human auditory evoked potentials I Evaluat  c07/1982  a15–240 v543 aIn an attempt to settle the long-standing controversy about the relative activity of nose, sternovertebral (SV), and other commonly used AEP reference sites, we recorded AEPs from a coronal chain of electrodes from the vertex to the tragus, extending down the neck, and from the nose, ear, mastoid process, knee and ankle. All electrodes were referred to a sternovertebral reference balanced to minimize EKG. Voltage gradients and wave forms corresponding to other references were derived by computer. Stimuli were presented at fixed durations after the R wave of the EKG and averages with no stimulus were subtracted from averages with click stimuli to minimize synchronized EKG activity in non-cephalic derivations.

Because the activity at a given electrode site cannot be determined in absolute terms, alternative reference sites must be compard by examining the relative location of each site in the total potential field. An indifferent electrode site defined in this manner is one at which the spatial and temporal voltage gradients are minimal over the duration of the activity of interest. AEP voltage gradients in this experiment were steepest in the temporal region, became extremely shallow at locations on the upper neck, and showed no detectable gradients below that point attributable to AEP activity. A gradient of this form was obtained in all subjects, in spite of significant intersubject differences in the magnitude of potentials in nose-SV derivations. Commonly used reference sites on the head such as the nose, ear and mastoid process, were shown to lie in regions of the AEP field characterized by significant voltage gradients over time and spatial location in most subjects. The balanced sternovertebral reference of Stephenson and Gibbs (1951) appears to be the best general choice for AEP recordings.10aSternum1 aWolpaw, Jonathan1 aWood, C., C.  uhttp://www.ncbi.nlm.nih.gov/pubmed/617751401880nas a2200169   4500008004100000022001400041245013300055210006900188260001200257300001200269490000700281520131900288653001801607100001701625700002101642856004701663       1982                        eng d  a0013-469400aScalp distribution of human auditory evoked potentials. II. Evidence for overlapping sources and involvement of auditory cortex.0 aScalp distribution of human auditory evoked potentials II Eviden  c07/1982  a25–380 v543 aThe scalp distributions of human auditory evoked potentials (AEPs) between 20 and 250 msec were investigated using non-cephalic reference recordings. AEPs to binaural click stimuli were recorded simultaneously from 20 scalp locations over the right hemisphere in 11 subjects. Computer-generated isovoltage topographic maps at high temporal resolution were used to assess the stability of AEP scalp distributions over time and relate them to major peaks in the AEP wave forms. For potentials between 20 and 60 msec, the results demonstrate a stable scalp distribution of dipolar form that is consistent with sources in primary auditory cortex on the superior temporal plant near the temporoparietal junction. For potentials between 60 and 250 msec, the results demonstrate changes in AEP morphology across electrode locations and changes in scalp distribution over time that lead to two major conclusions. First, AEPs in this latency period are generated by multiple sources which partially overlap in time. Second, one or more regions of auditory cortex contribute significantly to AEPs in this period. Additional data are needed to determine the relative contribution of auditory cortex sources on the superior temporal plane and the lateral temporal surface and to identify AEP sources outside the temporal lobe.10aTemporal Lobe1 aWood, C., C.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/6177515