Evoked Response Technique Research Articles

Auditory sensitivity to local stimulation of the head surface in a beluga whale (Delphinapterus leucas).

Using the auditory evoked response technique, sensitivity to local acoustic stimulation of the ventro-lateral head surface was investigated in a beluga whale (Delphinapterus leucas). The stimuli were tone pip trains of carrier frequencies ranging from 16 to 128 kHz with a pip rate of 1 kHz. For higher frequencies (90-128 kHz), the low-threshold point was located next to the medial side of the middle portion of the lower jaw. For middle (32-64 kHz) and lower (16-22.5 kHz) frequencies, the low-threshold point was located at the lateral side of the middle portion of the lower jaw. For lower frequencies, there was an additional low-threshold point next to the bulla-meatus complex. Based on these data, several frequency-specific paths of sound conduction to the auditory bulla are suggested: (i) through an area on the lateral surface of the lower jaw and further through the intra-jaw fat-body channel (for a wide frequency range); (ii) through an area on the ventro-lateral head surface and further through the medial opening of the lower jaw and intra-jaw fat-body channel (for a high-frequency range); and (iii) through an area on the lateral (near meatus) head surface and further through the lateral fat-body channel (for a low-frequency range).

Objective measurement of olfactory function by an Evoked Response Technique

Objective measurement of olfactory function by an Evoked Response Technique

Sensory nerve conduction velocities in the cutaneous afferents of the ulnar and peroneal nerves of the dog: Tissue temperature-dependent reference ranges

Sensory nerve conduction velocities in the cutaneous afferents of the ulnar and peroneal nerves of the neurologically normal adult dog were determined by stimulation at stimulus intensities of 15, 20 and 25 V through subcutaneously placed electrodes and by the averaged evoked response technique. Stimulus intensities of 15 V for the ulnar nerve and 20 V for the peroneal nerve were adequate to measure the sensory nerve conduction velocities of these nerves. A linear relationship was seen between sensory nerve conduction velocity (y in m/s) and tissue temperature (x in degree C) and the regression equations were expressed as follows: y = 1.6x + 12.3 at a stimulus intensity of 15 V for the ulnar nerve and y = 2.0x - 10.6 at 20 V for the peroneal nerve, respectively. The 95% confidence limits of the regressions of the sensory nerve conduction velocities against tissue temperature, obtained at a stimulus intensity of 15 V for the ulnar nerve or at a stimulus intensity of 20 V for the peroneal nerve, were proposed for a tissue temperature-dependent reference range to enable the clinician to evaluate graphically the sensory nerve conduction velocity in a diseased dog.

Auditory brainstem evoked response in at risk children.

Development of speech and language skills in children depends greatly on the effective hearing function. Early detection of any auditory deficit and institution of rehabilitation measures are the key to success in the total management of such hearing handicaps. Twenty at risk children were studied and their hearing function evaluated employing auditory brainstem evoked response technique (ABER). Auditory deficit was detected with the help of this technique as early as at 1 month of age. The risk factors in this study chiefly included hydrocephalus, neonatal jaundice requiring, exchanged blood transfusion, head injury during childhood and congenital ear deformity. Auditory evoked response technique provides the most reliable objective information about the hearing threshold of a child normal or handicapped. It can assess hearing function even at birth and thus it greatly helps in the management of hearing handicapped children at an early date.

The afferent fiber population mediating the thermal evoked response to skin cooling in man

A population of cold-responding fibers with response properties similar to those innervating primate skin were determined to be mediating the thermal evoked response to skin cooling in man. Cerebral evoked responses to a 10°C cooling pulse were recorded from human scalp at a 29°C adapting temperature where primate cold-responding fibers possess a considerable dynamic sensitivity. No time-locked cortical responses were reliably recorded from the 40°C adapting temperature to the same cooling pulse. At 40°C, thermally sensitive mechanoreceptors mediated by Aβ and large Aδ fibers possess their maximal sensitivity. In primate skin, specifically sensitive cold receptors are innervated by the small Aδ fiber group. The results of this study, then, suggest the existence of a small myelinated fiber group in human radial nerve, implying that the difficulty in recording from these fibers directly using microneurographic techniques in humans involves technical-morphological considerations. The results have implications for the utility of the cerebral evoked response technique as a clinical diagnostic tool, and the organization and representation of cortical temperature information in humans.

The spectral sensitivities of isolated human color mechanisms determined from contrast evoked potential measurements

Previous attempts to measure human spectral sensitivity curves by physiological methods have not yielded results with the precision and over a sufficiently wide intensity range to enable useful predictions to be made about the fine details of color vision. In the present experiment we have used a contrast evoked response technique to measure a set of spectral sensitivities whose quality is comparable to that of psychophysically obtained data. For this purpose a visual stimulus was prepared that would presumably be seen as a pattern by only one color mechanism. The EP data obtained from one rod-monochromat correspond well with the CIE 1951 scotopic relative luminous efficiency function, whereas the data from normal and dichromatic subjects resemble several of Stiles' πμ mechanisms. At the long wavelength end of the visible spectrum the relative peak sensitivities and the shapes of the spectral sensitivity functions closely agree with Stiles' π4 and π5 mechanisms. The spectral sensitivity of the short wavelength mechanism had the form of either the π1 or π3 mechanism. The dichromat results can be fitted by the same mechanisms. The long wavelength mechanism of a protanope resembled π4 and that of a deuteranope π5.

Sensory and motor representation in the cerebral cortex of the three-toed sloth ( Bradypus tridactylus)

Cortical sensory receiving areas were studied in 32 specimens of the three-toed sloth, Bradypus tridactylus, using the evoked response technique and barbiturate anaesthesia. Somatotopic organization in the somesthetic first area (S-I) was shown to be similar to that reported in higher mammals. The area devoted to the representation of the forelimb was considerably larger than that for the remaining body parts. The second somatosensory area (S-II), showing bilateral representation without a precise topographical organization, was identified in the rostral portion of the ectosylvian gyrus. Visual and auditory projections, occupying restricted areas, were found along the caudal banks of the ectosylvian fissure. Electrically excitable cortical motor area was explored in 8 animals anesthetized with diallyl barbituric acid in urethane. The motor representation of the various body parts was shown to coincide with the sensory projections, demonstrating the existence in a Eutherian mammal of a sensorimotor amalgam, identical to that described in marsupials. These findings suggest that sloths display a primitive pattern of neural organization, and that the sensory motor amalgam is a generalized form of cortical organization of primitive Therian mammals.

Audiometric and histological correlates of exposure to 1-msec noise impulses in the chinchilla.

Monaural chinchillas were exposed to 50 impulses of either 155-, 161-, or 166-dB peak SPL. The impulses had an A duration of 1 msec. Quiet threshold was measured at 0.25, 0.5, 1, 2, 4, and 8 kHz using the average evoked response technique. Recovery was monitored for 31 days; the animals were then sacrificed for surface-preparation histology. The median PTS at all frequencies was determined for each level of the impulse. The 155-dB level produced essentially no PTS, but each animal showed large and consistent outer hair-cell (OHC) lesions, 6 to 12 mm from the apex. The 161-dB level produced a dichotomy of results, with some animals showing no PTS and no hair-cell loss, while others had substantial PTS with attendant large hair-cell losses. The 166-dB group was consistent in showing a median 5–15-dB PTS with all animals having substantial hair-cell lesions. Micrographs are presented which show some of the structural and vascular alterations in the cochlea after impulse noise exposure.

Audiometric and histological effects of exposure to three levels of reverberant impulse noise

Monaural chinchillas were exposed to 140, 150, or 155 dB peak SPL impulses with 200-msec B-duration. Each animal received 50 impulses, 1/min. Thresholds were estimated by the auditory evoked response technique at 0.5, 1, 2, 4, and 8 kHz before and after exposure. Animals were sacrificed at 30 days postexposure for surface preparation. The 140-dB group sustained no permanent hearing losses and had normal cochleas. The cochleas of the 150-dB group ranged from normal to severe losses of both OHC and IHC. The 155-dB group had consistently large cochlear lesions. The magnitude of cochlear lesions is not always completely reflected in the audiograms. The cocklear lesions induced by the reverberant impulse are compared to the lesions caused by 1-msec and 40-μsec A-duration impulses. Finally, the data are discussed in terms of the present impulse noise damage risk criteria. [Study supported by Grant No. 1RO1 OH 00364-01, National Institute for Occupational Safety and Health, Public Health Service, Department of Health, Education and Welfare.]

Asymptotic temporary threshold shift in chinchilla measured by the auditory evoked response

Monaural chinchilla were exposed to octave-band noise (4 kHz center frequency) at 80 dB SPL for 96 hours. Quiet thresholds at 1, 2, 4, and 8 kHz were estimated before, during, and after the noise exposure using the auditory evoked response technique. The greatest threshold shift that was measured occurred at 24 hours after noise onset; then hearing level recovered by approximately 5 dB to an asymptotic level. After cessation of the noise, hearing returned to normal by 72 hours. The results agree with previous behavioral studies of asymptotic TTS [Mills, “Threshold Shifts Produced by Exposure to Noise in Chinchillas with Noise-Induced Hearing Losses,” (in press)] in showing comparable levels of TTS, and also that the hearing level during the noise exposure is determined by the level of the noise rather than the animal's preexposure threshold. [Study supported by Grant No. 1RO1 OH 00364-01, National Institute for Occupational Safety and Health, Public Health Service, Department of Health, Education and Welfare.]

The Role of the Middle Ear in Acoustic Trauma from Impulses

The purpose of this experiment was to evaluate the role of the middle ear in acoustic trauma following high-level impulse noise exposure. Eleven monaural chinchillas were exposed to either 161- or 166-dB peak SPL impulses of 1-msec “A” duration, presented at the rate of 1 per minute for 50 minutes. Auditory thresholds were measured before and at regular intervals after exposure, using the evoked response technique; middle-ear status was evaluated by means of impedance tympanometry. At 30 days the animals underwent tympanotomy for middle-ear examination followed by sacrifice for surface preparation histology. The 161-dB group showed the widest range of TTS with two animals exhibiting PTS. Tympanometric examination was suggestive of tympanic membrane stress (i.e., double-peaked tympanograms). The 166-dB group showed moderate TTS but no PTS; however, all animals had tympanic membrane perforations which required 10 to 30 days to heal. No gross changes were observed in the ossicular chains at tympanotomy. The results will be discussed in terms of a potential mechanism for histologic variability and individual susceptibility.

The Interaction of Continuous and Impulse Noise: Audiometric Effects

Continuous and impulse noises, considered “safe” by existing damage risk criteria (DRC), were combined to model more realistic noise environments. Monaural chinchillas (23) were exposed to one of the following conditions: (a) 95 dB SPL continuous noise at 2–4 kHz for 1 h; (b) 50 impulses with a 40-μsec A duration at 158 dB SPL peak pressure; (c) interrupted combination of the continuous and impulse noise with the continuous noise off for 2 sec during the impulse delivery; (d) superimposed combination of the continuous and impulse noise. Quiet thresholds were measured before and after exposure at 0.25, 0.5, 1, 2, 4, and 8 kHz using the averaged evoked response technique. Recovery was monitored for 31 days. The median recovery from the 95 dB SPL continuous and 158 dB impulse was complete by 30 h. The interrupted combination produced temporary threshold shifts (TTS) of 50–60 dB at 2, 4, and 8 kHz that required four days to recover. The superimposed combination produced, 30 dB TTS at 0.25, 0.5, and 1 kHz, 70–90 dB TTS at 2, 4, and 8 kHz, and a final median audiogram typical of noise induced sensorineural hearing loss with 30–40 dB PTS at 2, 4, and 8 kHz.

Audiometric and Histological Effects of Exposure to 40-μsec High Level Impulses

Monaural chinchillas (15) were exposed to 50 impulses of either 158, 615, or 175 dB peak SPL. The impulses were generated by a spark-gap source, which produced an impulse with a 40-μsec A duration. Quiet thresholds were measured at 0.25, 0.5, 1, 2, 4, and 8 kHz, using the averaged evoked response technique. Recovery was monitored for 31 days and then the animals were sacrificed and their cochleas were analyzed using the surface preparation technique. The three exposures produced virtually no permanent threshold shifts (PTS) with the exception of 10–30 dB PTS in one animal in each of the 165- and 175-dB groups. However, hair cell losses were seen in all three groups. The cochleagrams varied from low level scattered losses to lesions of the OHC that spanned a 4-mm stretch in the base of the cochlea. The IHC losses were considerably smaller and more restricted. The audiograms do no necessarily reflect the state of the cochlea.

Variability in averaged evoked response audiometry

Average evoked response technique was presented as a method useful in the diagnosis of disorders of hearing and language. The variation of the individual evoked responses concealed in the average is a possible limitation of the method's continued clinical acceptability. Characteristics of this variability and three methods amenable for clinical assessment were discussed. It was concluded that average evoked response measurements are inadequate without variance measurements.

Evoked response audiometry: psychiatric patients.

Averaged evoked auditory responses were recorded during two experiments with subjects hospitalized for psychiatric disorders. Subjects from experiment 1 were testable by conventional pure tone audiometry and subjects from experiment 2 were untestable by conventional pure tone audiometry. Results indicated that evoked auditory responses obtained from subjects during experiment 1 were similar to those reported for normal subjects. When used as a diagnostic technique with the subjects from experiment 2 the evoked response technique was less effective than with the subjects from experiment 1. Both experimental groups had subjects who could not be tested by the evoked response technique.

Application of the evoked response technique in air pollution toxicology

The evoked response to flash in the specific visual cortex and in the superior colliculus of unrestrained and unanesthetized albino rats bearing indwelling bipolar electrodes was investigated with the use of an on-line digital computer. It was anticipated that this method might provide a useful technique that might not only be more sensitive and reliable than morphologic and biochemical methods, but also might provide some insight into the site of action of toxic agents on the central nervous system. The effect of exposure to carbon monoxide as recorded by the technique of the evoked response was similar to that of exposure to pentobarbital. The response to respiratory exposure to ozone differed from that induced by carbon monoxide and pentobarbital. It was concluded that the technique of the evoked response could be a helpful tool in air pollution toxicology. The results are reproducible and the method shows great sensitivity. Data can be accumulated in a reasonably short time, especially if animals with indwelling electrodes are maintained continuously in the laboratory.