Effects Of Stimulus Repetition Rate Research Articles

The Effects of Stimulus Repetition Rate on Electrically Evoked Auditory Brainstem Potentials in Postlingually Deafened Adult Cochlear Implant Recipients.

Background: By using outcome prediction scores, it is possible to distinguish between good and poor performers with cochlear implants (CI) after CI implantation. The reasons for poor performance, despite good basic conditions, can be manifold. On the one hand, the postoperative fitting may be inadequate; on the other, neurophysiological disease processes may impair speech understanding with a CI. These disease processes are not yet fully understood. In acoustics, it is known that the auditory brainstem responses (ABR) and their latencies and amplitudes allow differential diagnosis based on reference values for normal-hearing individuals. The aim of this study was to provide reference values for electrically evoked brainstem responses (EABRs) in terms of rate-dependent latencies and amplitudes. Methods: 20 ears of 18 experienced adult CI recipients with a predicted and measured good postoperative word recognition score were recruited from the clinic's patient pool. In the same stimulation mode and intensity we measured latencies and interpeak-latencies of EABRs and electrically evoked compound action potentials (ECAPs). With a defined supra-threshold stimulation intensity above the individual ECAP threshold, we applied stimulation at several rates between 11 and 91 stimuli per second. Results: We found rate dependences for EABR latency t3 and t5 in the order of 0.19 ms and 0.37 ms, respectively, while ECAP was not affected by rate. Correspondingly, the interpeak intervals' rate dependences for t5-t1, t5-t3 and t3-t1 were of the order of 0.37 ms, 0.18 ms and 0.19 ms. Comparing the EABR amplitudes between the stimulation rates 11/s and 81/s, we found that at 81/s the amplitudes were significantly reduced down: to 73% for A3 and 81% for A5. These rate dependences of latency and amplitude in EABR have characteristics comparable to those of acoustic ABR. Conclusions: These data may serve to provide reference values for EABR and ECAP latencies, interpeak intervals and amplitudes with respect to stimulation rate. Altered response patterns of ECAPs and EABRs to normalised stimulation modes could be used in the future to describe and classify neuropathological processes in a better-differentiated way.

Effect of Stimulus Rates in Chirp and Click Evoked Auditory Brainstem Response in Adults with Normal Hearing Sensitivity

Introduction The effects of increasing stimulus repetition rate on the ABR using click stimuli have been investigated in normal and hearing impaired subjects with neurologic abnormality but there is limited study on the effect of stimulus repetition rate on ABR using chirp stimuli. The present study aims to compare the chirp evoked auditory brainstem responses with reference to changes in latency of peaks, interaural latency differences and interwave latency intervals as a function of rate and compare those responses with the click evoked auditory brainstem responses, in normal hearing subjects. Materials and Methods Total 30 normally hearing adults were considered for this study. All participants were screened for normal hearing sensitivity upto 8 kHz in pure tone audiometry for middle ear pathology and central auditory processing disorder. Four parameters of ABR were considered to assess in this study including absolute latency, interwave latency intervals, latency-rate function and interaural latency. ABR was done based on the protocol of this study. Results Results revealed that there was a significant difference in the absolute latency and interwave intervals when the stimulus repetition rate was increased. Conclusion The latencies of wave III and V increases and waveform morphology changed as the stimulus repetition rate increased above 20/sec. The absolute latency of wave III and V was found to be shorter than clicks and can be used especially in newborn hearing evaluation assuming in shorter time window.

Habituation and sensitization of aggression in bullfrogs (Rana catesbeiana): testing the dual-process theory of habituation.

The aggressive response of male bullfrogs (Rana catesbeiana) habituates with repeated broadcasts of acoustic stimuli simulating a new territorial neighbor. The effects of stimulus repetition rate and stimulus intensity on bullfrog aggressive responses were tested in a field experiment designed to test the assumptions of a dual-process theory of habituation. Synthetic advertisement calls were broadcast at 2 repetition rates and 2 intensities in a factorial design. Bullfrogs were more aggressive at the higher stimulus intensity at both repetition rates. Aggressive responses habituated more slowly at the higher stimulus intensity and slower repetition rate compared with other treatments. Several biotic and abiotic factors had small or negligible effects on aggressive responses. Although consistent with the operation of 2 opposing processes, habituation and sensitization, the data provide only partial support for the assumptions of dual-process theory.

Pre- and postcentral somatosensory evoked potentials in Huntington's disease: Effects of stimulus repetition rate

We recorded frontal, central and parietal somatosensory evoked potentials (SEPs) to median nerve stimulation in 20 patients with Huntington's disease (HD) and in a group of normal controls. Two stimulus repetition rates, 1 Hz and 5 Hz, were employed. In HD patients the early cortical potentials (latency range 20–30 ms) at all 3 recording locations were replaced by a widespread, broadly configured N20-25 deflection, while later potentials at 40–80 ms did not significantly differ from those of normals. In contrast to the early P22, P27 and N30 potentials in normals, the N20-25 potential in the patients was not significantly modified by changing the stimulus repetition rate. At 40–80 ms the stimulus rate effects were similar in the patients and normals. The results show that early pre- and postcentral SEPs are both pathological in HD, while later frontal and parietal components can be totally preserved. The early N20-25 in HD is possibly a subcortical potential, seen due to unmasking in the absence of early cortical deflections.

The effect of stimulus repetition rate on the diagnostic efficacy of the auditory nerve-brain-stem evoked response

This study investigates the hypothesis that an increase in the click presentation rate during diagnostic testing with the auditory nerve-brain-stem response (ABR) will increase the efficiency with which lesions may be detected in the nervous system. Cats were exposed to conditions of hypoxia, hypercapnia and acidemia, and hypoglycemia was induced in rats. ABR was recorded using the standard 10/sec click rate and also a higher (55/sec) rate during both the control state and the experimental state. Various parameters of the ABR were compared at the two click rates in the control and experimental states to see if the higher click rate was more effective in detecting pathology in the nervous system. It was found that in only a very few cases was the higher stimulus presentation rate more effective, and that in general ABR recordings at one stimulus rate only is quite sufficient for work in a clinical setting.

Effects of stimulus repetition rate on ABR threshold, amplitude and latency in neonatal and adult Mongolian gerbils

The ABR wave forms of 16-day-old and adult Mongolian gerbils were evoked by click stimuli presented at rates ranging from 1 to 80/sec. Wave I and wave IV thresholds were determined for each of 5 click rates. Amplitudes and latencies of waves I and IV were measured at each of 7 click rates and 3 intensity levels (15, 40 and 65 dB above threshold). Thresholds for waves I and IV in the adult gerbil and wave I in the 16 day gerbil were unaffected by changes in stimulus repetition rate. Neonatal wave IV thresholds were unaffected by click rate for rates below 25/sec but increased approximately 7 dB/decade increase in click rate when rate exceeded 25/sec. Increasing click rate produced greater reductions in ABR amplitude among neonates than adults for both waves I and IV. Decreases in amplitude due to increasing rate were independent of intensity level in both neonatal and adult subjects. Increasing rate produced similar increases in wave I latency among 16 day and adult subjects, but produced much greater increases in wave IV latency among neonates. Stimulus intensity level and click rate acted independently on wave I and wave IV latency in adult subjects and wave I latency in neonates. However, an interaction between rate and intensity was observed with respect to neonatal wave IV latency.

The effect of stimulus repetition rate on interaural ABR latency differences in normal and hearing-impaired subjects

Twenty-five subjects with normal hearing and 15 with bilateral high-frequency sensorineural hearing impairment were presented click stimuli at four repetition rates (11, 33, 67, and 89 clicks/s) to access interaural symmetry of wave V latency and amplitude. Predictably, amplitude was significantly decreased and latency increased across all subjects at the higher repetition rates. In both groups, however, interaural latency differences (ILDs) remained with the 0.3-ms normal criterion previously established for slow repetition rates. Thus, both abnormal repetition rate effects and interaural latency differences can serve as reliable indicants of retrocochlear auditory dysfunction, even when peripheral hearing impairment exists.

The effect of stimulus repetition rate on the auditory brainstem response in tumor and nontumor patients.

Auditory brainstem responses were recorded in two groups of adult subjects with asymmetric sensorineural hearing loss. Clicks were presented at repetition rates of 9.7, 39.7, 49.7, and 59.7/s. One group was composed of 20 patients with no known otoneurologic lesion (cochlear group), and one group was composed of 8 patients with a surgically confirmed acoustic neuroma in the ear with poorer hearing sensitivity (retrocochlear group). Detection of wave V at different repetition rates was not significantly different between the two groups. Average wave-V latency shift was not significantly different between the two groups as repetition rate increased from 9.7/s to 39.7/s but was significantly greater for the retrocochlear group as repetition rate increased from 9.7/s to 49.7/s and 59.7/s. However, the wave-V latency shift showed no improvement over the slow-rate interaural wave-V latency difference in discriminating between the two groups of patients. No significant correlation between the amount of wave-V latency shift and hearing loss at 2000 Hz or 4000 Hz was found for the ears with poorer hearing sensitivity.

Effects of stimulus repetition rate on slow and fast components of auditory brain-stem responses

Effects of stimulus repetition rate on the slow and fast components of the auditory brain-stem response (ABR) were investigated in 10 adult subjects with normal hearing. The ABRs were recorded with click stimuli at repetition rates of 8, 13.3, 23.8, 40 and 90.9/sec and at an intensity level of 55 dB nHL. Power spectral analysis of the averaged responses was performed. Then the responses were divided into a slow component (0–400Hz) and a fast component (400–1500 Hz) by using digital filtering technique. The magnitude of the slow component was little affected with increasing stimulus rate from 8/sec to 90.9/sec, while successive waves of the fast component, including wave V, decreased in amplitude as stimulus rate was increased. The latency of the slow component and each wave of the fast component was prolonged with increasing click rates. The shift of latency became longer in the later waves than in the earlier waves.

Effects of stimulus repetition rate and frequency on the auditory brainstem response in normal cochlear-impaired, and VIII nerve/brainstem-impaired subjects.

The effects of signal repetition rate and frequency on the auditory brainstem responses of normal listeners, of persons with cochlear lesions, and of persons with VIII nerve/brainstem lesions were evaluated. The normal group exhibited more waves I and II than did the cochlear and VIII/brainstem groups. The normal and cochlear groups exhibited more waves III and V than did the VIII nerve/brainstem group. The latency of wave I was not different among groups, whereas wave V was significantly later in the VIII nerve/brainstem group than in the other groups. Waves I, III, and V were later for 50/s than for 10/s. Waves I and III displayed shorter latencies for 4000 Hz than for 2000 Hz, whereas wave V displayed similar latencies for the two stimuli. In conclusion, cochlear pathology (less than or equal to 65 dB HL) does not prolong the latencies of waves I and V. A dual mechanism is discussed to explain the rate-dependent latency shift of wave V.

Low frequency depression of the H wave in normal and spinal man

The effects of stimulus repetition rate on the H wave amplitude of intact and spinal cord injury patients were studied. Stimulus repetition rates ranging from 1 shock/10 sec to 10 shock/sec were employed. Each stimulus train consisted of twenty-five repetitive shocks. Summated responses were obtained by use of a computer of average transients and an X-Y plotter. In the intact subject, the H wave displayed a progressive reduction in amplitude at increasing rates of repetitive stimulation. The profile of depression in this frequency-amplitude series was similar to the low frequency depression that occurs in monosynaptic reflex pathways of anesthetized, decapitated and spinal animals when subjected to repetitive stimulation over the same frequency range. A variety of evidence is presented to suggest the same depressive phenomenon is operative in the H wave of man and the monosynaptic reflex of experimental animals. The H wave of spinal cord injury patients displayed virtually no low frequency depression on days of diminished spasticity. On days of heightened spasticity H wave amplitude was low and low frequency depression was evident. These results are thought compatible with the theory that low frequency depression is mediated by interneuronal circuits, including possibly the Renshaw cell system. These circuits would appear hypoactive on days of diminished spasticity and hyperactive on days of heightened spasticity. Evidence from a variety of sources is presented to support this theory.