ABSTRACT
Brain-stem auditory evoked responses (BAERs) were recorded both to rarefaction and condensation click stimuli in 92 normal hearers and 78 patients with varying degrees of cochlear hearing loss (N = 340 ears). Frequency distributions of rarefaction minus condensation (R - C) latency and amplitude differences revealed clinically significant polarity effects in a substantial percentage of the patients studied. Bivariate plots of R - C latency and amplitude differences versus average high frequency hearing loss (PTA 3) demonstrated that the magnitude of the R - C latency and amplitude differences also seemed to be influenced by degree of high frequency hearing loss. Results are discussed relative to the phase-locking properties of the afferent auditory nerve fibers and the possible electrodiagnostic consequences of recording the BAER either to alternating or condensation clicks.
Subject(s)
Brain Stem/physiology , Electroencephalography , Evoked Potentials, Auditory/physiology , Acoustic Stimulation , Adolescent , Adult , Aged , Aged, 80 and over , Cochlear Diseases/physiopathology , Female , Humans , Male , Middle Aged , Reaction TimeABSTRACT
A model of the 40 Hz auditory event-related potential (40 Hz AERP) was developed and evaluated in a group of normal subjects and two patient groups. The model views the 40 Hz AERP as a combination of the brain-stem auditory evoked potential (BAEP) and a sinusoidal component presumed to arise from structures rostral to the brain-stem. Fourier analysis techniques were used to quantify changes in the sinusoidal component. The results obtained demonstrated that the phase of the sinusoidal component was quite stable in normal subjects, but was predictably altered as a consequence of thalamic or midbrain lesions. Lesions of the temporal lobe did not alter the phase of the sinusoidal component. These results were interpreted as being consistent with the model developed and suggesting a midbrain or thalamic origin for the 40 Hz sinusoid.
Subject(s)
Evoked Potentials, Auditory , Mesencephalon , Temporal Lobe , Acoustic Stimulation , Adult , Brain Diseases/physiopathology , Female , Humans , Male , Reference ValuesABSTRACT
The use of the visual evoked potential (VEP) was investigated in terms of its ability to accurately reflect the behaviorally determined extent of the visual field in non-verbal subjects. Two major adult groups of cats were studied: normals, and those with neonatal section of the corpus callosum at 15-19 postnatal days of age. A light-emitting diode was used as the visual stimulus. For both groups, the VEP determined monocular visual field extent closely matched the behaviorally determined field extent (Elberger 1979). This indicates that the VEP method is accurate, and that it is sensitive enough to detect differences between different populations of subjects.
