The overall goal of this project is to advance basic science knowledge of the ABR (Auditory Brainstem Response), recorded in humans, based upon recent developments in multi-channel recordings. Several lines of research will be pursued. First, it will be determined whether the ABR in humans, in whole or in part, can be modelled as an equivalent dipole. Humans will be studied recording from electrodes placed on the scalp according to the standard 10-20 system. Two lines of evidence will be used to determine if the potentials are consistent with an eccentric dipole generator: a) comparison of the dipole generator estimated from two different electrode arrays. b) comparison of the surface potential distribution of the ABR at each point in time, with potentials recorded from dipoles placed in a volume-conductor molded from the head of the subject. The testing of surface potential distribution related to a dipole in the internal auditory meatus will also contribute to the question as to whether wave II of the ABR is due to the VIIIth nerve action potential entering the cranium. Second, the effects of signal filters on the ABR waveforms will be studied as they affect the orientation, magnitude, or detection of the equivalent dipole. Third, the effects of muscle artifacts on the potentials recorded at different scalp locations will be determined, as well as whether nearfield muscle recordings provide a better means of excluding artifact-containing sweeps. Finally, the signal-to-noise ratio of different electrode locations for recording the ABR in humans will be studied in order to determine the optimal locations for electrodes. This research is directly related to the medical uses of the ABR, which includes diagnosis of hearing deficits in newborns, infants, and adults, as well as diagnosis of neurological abnormalities in children and adults.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
7R01DC000328-06
Application #
3216587
Study Section
Hearing Research Study Section (HAR)
Project Start
1991-07-01
Project End
1994-02-28
Budget Start
1991-08-15
Budget End
1992-02-29
Support Year
6
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Abratech Corporation
Department
Type
DUNS #
624508917
City
Sausalito
State
CA
Country
United States
Zip Code
94941
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Zhang, Z (1995) A fast method to compute surface potentials generated by dipoles within multilayer anisotropic spheres. Phys Med Biol 40:335-49
Fletcher, D J; Amir, A; Jewett, D L et al. (1995) Improved method for computation of potentials in a realistic head shape model. IEEE Trans Biomed Eng 42:1094-104
Jewett, D L; Zhang, Z (1995) Multiple-generator errors are unavoidable under model misspecification. Electroencephalogr Clin Neurophysiol 95:135-42
Zhang, Z; Jewett, D L; Goodwill, G (1994) Insidious errors in dipole parameters due to shell model misspecification using multiple time-points. Brain Topogr 6:283-98
Gerson, J; Cardenas, V A; Fein, G (1994) Equivalent dipole parameter estimation using simulated annealing. Electroencephalogr Clin Neurophysiol 92:161-8
Zhang, Z; Jewett, D L (1994) DSL and MUSIC under model misspecification and noise-conditions. Brain Topogr 7:151-61
Zhang, Z; Jewett, D L (1994) Model misspecification detection by means of multiple generator errors, using the observed potential map. Brain Topogr 7:29-39
Raz, J; Biggins, C A; Turetsky, B et al. (1993) Frequency domain dipole localization: extensions of the method and applications to auditory and visual evoked potentials. IEEE Trans Biomed Eng 40:909-18
Cardenas, V A; Gerson, J; Fein, G (1993) The reliability of P50 suppression as measured by the conditioning/testing ratio is vastly improved by dipole modeling. Biol Psychiatry 33:335-44

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