Subject(s)
Acoustic Stimulation/methods , Cochlear Implants , Deafness/epidemiology , Deafness/surgery , Evoked Potentials, Auditory, Brain Stem/physiology , Adolescent , Adult , Age Distribution , Case-Control Studies , Child , Child, Preschool , Deafness/diagnosis , Electric Stimulation/methods , Female , Follow-Up Studies , Humans , Male , Reference Values , Risk Factors , Sex Distribution , Treatment OutcomeABSTRACT
OBJECTIVE: Derivation dependence, inter- and intrasubject/intertest variability, bilateral differences of the eardrum vibration characteristics have been investigated using laser Doppler vibrometry (LDV). MATERIAL AND METHODS: A total of 31 normally hearing adults were examined. In each subject, both ears were consecutively stimulated by the chirp acoustic stimulus that covered 500-3700-Hz frequencies. The laser beam was directed to and the reflection was consecutively picked up from the tympanic membrane surface. RESULTS: LDV curves derived from different eardrum loci possessed dissimilar characteristics. The derivation area dependence was particularly apparent for the stimulus frequency constituents above 1500 Hz. The intersubject variability of LDV parameters exceeded the intrasubject/intertest one. The intersubject divergences looked selectively distinct for the frequencies over 2000 Hz. Under repeated recordings, LDV parameters remained stable. The intertest differences, if appeared, concerned predominantly the magnitudes of separate frequency bands. LDV waveforms registered by experienced and beginner investigators were alike. Bilaterally derived LDV curves regularly differed from each other. In individual cases, the bilateral divergences approximated the intersubject deviation. CONCLUSIONS: The derivation area on the eardrum should be taken into account when estimating the actual LDV recording. Over repeated recordings in separate individuals, LDV waveforms are stable while the experience of investigator has slight if any influence on the principal LDV characteristics. Due to bilateral differences in the middle ear transfer function, in LDV testing of the ear suspected to the pathology, LDV recording from the opposite healthy ear could hardly be taken as an appropriate reference sample.
Subject(s)
Ear, Middle/physiology , Hearing Loss, Conductive/diagnostic imaging , Hearing Loss, Conductive/diagnosis , Tympanic Membrane/physiology , Vibration , Acoustic Stimulation , Adult , Audiometry , Female , Humans , Laser-Doppler Flowmetry , Male , Middle Aged , Models, Biological , UltrasonographyABSTRACT
The bounce phenomenon has been investigated in humans, evaluating alterations of click evoked otoacoustic emission (EOAE) after presentation of 250-Hz frequency loud tones during 3 min. EOAE changes were manifested in initial augmentation followed by reduction, peaking at 1 and 3 min of post-exposure time, respectively. Recoveries took 5-7 min afterwards. Under linear and nonlinear EOAE acquisition modes both manifestations of bounce appeared similar. At lower exposure intensities, 65-75dB SPL, augmentations prevailed over reductions. At higher intensities, 80-95 dB SPL, augmentations and reductions were of similar magnitudes. At highest intensity, 100 dB SPL, an obvious EOAE drop has hardly been preceded by any augmentation. Based upon these data, the bounce is considered to be a compound of two opposite events, appearance of each being dependent upon the exposure level. Subjects with high bounce indices in one ear displayed comparable indices in other ear too. Low bounce magnitudes were accordingly typical for particular subjects irrespective of the ears tested. EOAE alterations were observed under ipsilateral, but not contralateral exposures of tones. It has been concluded therefore that the bounce involves peripheral receptor rather than central neural mechanisms. No EOAE shifts were seen under application of clicks without any low-frequency exposure tones. Correspondingly, the bounce is judged to reflect inner-ear processes triggered by low-frequency tones, but not by regular presentations of test-stimuli.
Subject(s)
Acoustic Stimulation/methods , Auditory Threshold , Hearing/physiology , Otoacoustic Emissions, Spontaneous , Adult , Ear/physiology , Female , Humans , MaleABSTRACT
Auditory P300 potentials obtained in cochlear implant users were evoked with tone bursts designed to reflect the frequency stimulation patterns of intracochlear electrodes. To visualize these stimulation patterns in MED-EL COMBI 40+ cochlear implants, we calculated color-coded plots of the charge of each stimulus pulse as a function of time and stimulation channel (stimulograms). The aim of this study was to investigate the effect of stimulation patterns on event-related potentials, such as the P300. The influence of electrode separation on the P300 response in postlingually deaf adults using a cochlear implant is demonstrated in two examples.