Short-latency auditory evoked potentials in the monkey. I. Wave shape and surface topography

The components and topography of the short-latency auditory evoked potentials (SLAEPs) in the monkey were analyzed using a combination of surface and epidural electrodes. Nine positive peaks, and a slow negativity following wave 7, are identified in the SLAEP recorded at the vertex referred to the mastoid ipsilateral to a monaural stimulus. Subcomponents of waves 1 and 3 are consistently observed, and other waves are probably compound as well. Barbiturate anesthesia results in latency prolongations which are cumulative across components but does not alter the component sequence. With binaural stimulation there is simple summation of the monaural responses for the components preceding wave 7, but a binaural interaction for wave 7. The polarity and clarity of the various components depend on the recording configuration selected. No single configuration is optimal for the demonstration of all components, and the use of montages with multiple electrodes may increase the information gained from clinical SLAEP recordings in man. The monkey SLAEP components can be grouped based on similarities of their surface topographies, which suggest similar anatomic orientations of their underlying generators. Probable homologues between the components of the simian and human SLAEP, based on temporal sequence, topography, and the effects of variation of the stimulus parameters, are: Jewett's waves I through VII correspond to monkey waves 1, 3, and 5 through 9. Due to differences in the size and shape of the heads, the monkey waves 2 and 4 correspond to negativities in the human SLAEP, labeled IN and IIN after the components which they follow. Another peak, with latency between waves 7 and 8 in the monkey and V and VI in man, is only clearly seen in the mastoid-to-mastoid linkage, contralateral negative.