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[Experiences with the implantation of a multichannel electrode in the acoustic nerve].

The authors developed a surgical approach to the acoustic nerve enabling the introduction of an electrode into the acoustic nerve. A multichannel electrode was implanted by this method in a deaf patient. The receiver casing for percutaneous transmission was fixed in the mastoid. Encouraging hearing results were obtained over a period of two months by electrical stimulation of the acoustic nerve.

Auditory Perception↗

Results and perspectives with extracochlear round window electrodes.

The results obtained with implanted electrodes at the round window are comparable to results with electrodes in the scala tympani or in the hearing nerve in respect to frequency and amplitude resolution with pulsatile and sinusoidal stimulation (with considerable interpatient variations). Although the subjective quality of the perceived sounds is expected to vary depending on the stimulation site, it seems that timing effects of electrical stimulation may play a major role in pitch perception as required for voice and sound recognition or prosody identification. Our technique is a safe procedure involving only routine middle ear surgery to place the induction coil within the mastoid bone and to put an electrode at the round window margin. By an external stimulator, sounds are transformed to electrical stimuli suited to excite surviving fibers of the cochlear nerve. This helps the patient to communicate and provides some basic cues for speech discrimination.

Adult↗

Temporal summation in normally and abnormally hearing chinchillas.

Young adult monauralized chinchillas (N:5) were conditioned to cross a barrier in response to 7 pure tones from .5-4 kc/s. Tone bursts were either 20- or 500-msec long. Individual S's yielded threshold data for the longer duration comparable to published norms. Group mn difference between thresholds at 20- vs 500-msec durations [i.e., temporal summation (TS)] was 7 db, or 4.7 db less than TS reported for normal chinchillas reported by Wall et al (J. Aud. Res., 1981, 21, 29-37) and others. One S yielded no TS. After exposure for 4 hrs to a 2-kc/s tone at 120 db SPL, group mn thresholds for the 20-msec tones were only 1 db poorer than those for 500-msec tones (i.e., negligible TS). TS is clearly altered in noise-induced hearing loss.

Acoustic Stimulation↗

[Age and features of cortical auditory evoked potentials].

Auditory evoked potentials (AEP) elicited by acoustic stimuli of various frequencies and intensities were studied in children aged from three to sixteen years. With age, peak latencies of the AEP components decrease on the average (taking into account the differences of such changes depending on the frequency and intensity of the stimuli presented) by 67.6 +/- +/- 13; 82.0 +/- 7.5; 65.6 +/- 7.2; 32.3 +/- 6.7 ms for components P1, N1, P2, N2 respectively. In 90% of the cases the thresholds of auditory sensations coincided with AEP thresholds; in 10% of the cases the thresholds of electrocortical reactions were by 5 dB lower than those of the auditory sensations. Enhancement of the stimulus to 80 dB lead to an increase of the AEP amplitude, while further augmentation of stimulus intensity in most cases resulted in a decrease of the AEP amplitude which was accompanied by unpleasant sensations or preceded their appearance. The frequency of this phenomenon drops with the age from 90% in 3-4 years old children, down to 30% in juveniles 15-16 years old.

Adolescent↗

Effects of stimulus frequency, level, and duration on auditory temporal ordering.

Auditory temporal ordering was investigated in 5 normal-hearing young adults. Ss made diotic 2IFC judgments for pure tones of 0.5, 1, 2, or 4 kc/s and critical-band noises centered at those frequencies, on duration (standard: 40 msec; variables: 10, 20, or 30 msec), level (standard: 70 db HL; variables: 40, 50 or 60 HL), and frequency (standard: 0.5 kc/s; variables: 1,2, or 4 kc/s). Interstimulus interval (ISI) was 5, 10, 20, 50, 100, or 200 msec. All stimuli were at 70 db HL except of course the variable stimuli in the level judgments. Performance improved with increasing ISI. Mean threshold ISIs (performance at 75%-correct) collapsed across pure tones and noise bands were 12.5, 6.25, and 6.25 msec for duration, level, and frequency, respectively. With ISI constant at 100 msec, ANOVAs revealed statistically significant differences among the variables for duration and for level but not for frequency (performance for frequency was nearly perfect at the shortest ISI). There were statistically significant differences between mean performance, and between mean threshold ISIs, for duration, level, and frequency, indicating that auditory temporal acuity is not independent of the kinds of sound, as has been suggested (Hirsh, J. Acoust. Soc. Am., 1959, 31, p. 759).

Adult↗

[Highpass filtering of auditory evoked brain stem potentials (author's transl)].

Twenty ears of normal-hearing subjects are investigated as to the influence of highpass filtering on latency, amplitude, and shape of auditory evoked brain stem potentials. For this purpose, three different Bessel-filters (steepness 24 dB/octave) with lower cut-off frequencies at 100, 200, and 300 Hz (3-dB down points) and an upper cut-off frequency at 3 kHz are used. Spectral composition of brain stem potentials is analyzed by digital filtering based on Fast Fourier Transformation. Results show decreasing latency and amplitude of the negative wave between Jewett V and VI with increasing lower cut-off frequency. With higher edge frequencies we find attenuation of wave V relative to wave IV amplitudes. For that reason we must assume that an essential part of brain stem activity is located below 300 Hz. In our experience moderate highpass filtering seems to be useful in neurological cases to eliminate low frequency components of the signal. In that way potentials I -- V are easy to be identified and interpeak latencies can be determined without any problems. For objective threshold determination, however, brain stem potentials should be derived preferably with broadband filter settings to improve correlation of tone audiometric hearing loss (at about 3 kHz) and brain stem response threshold. A filter set with different lower cut-off frequencies has proved to be really useful in routine work. However, it must by taken into account that highpass filtering means an alteration of the original response in any case.

Audiometry↗

[Responses of cat caudate nucleus neurons to acoustic stimulation].

Reactions of 141 cat caudate nucleus neurons to auditory signals--tone (500 and 2000 Hz) and clicks with different frequency (0.2 and 0.8/s) and intensity (75, 80, 95 dB) were recorded extracellularly. Neuronal reactions were highly variable as to the character of responses (phasis, tonic), their structure (one or two phases of activation), latent periods (from 7.5 to 300 ms), discharge frequency in burst responses (from 90 to 800 imp/s). Analysis of the averaged poststimulus histograms and plots of the dynamic reaction modifications showed that in most units (74%) the responses became considerably better expressed in case of a decreased stimulus frequency: the response regularity and the number of spikes in each response rose. The neuronal reactions also increased and acquired more distinct time structure with an increase in the stimulus intensity, 17% of recorded units showed qualitative differences in the character of neuronal reactions to clicks and tones: phasic activation arosed to clicks and tonic change of pulse activity occurred to tones. Peculiarities of the caudate nucleus neuronal reactions to auditory stimuli with different parameters are discussed.

Animals↗

Averaged electrode voltages: management of electrode failures in children, fluctuating threshold and comfort levels, and otosclerosis.

Implant-generated surface potentials, or averaged electrode voltages (AEVs), were collected by means of the electrode-by-electrode (E-E) mapping variable mode strategy. Three topics were investigated. 1) Eighteen children under the age of 7 were tested and the E-E map of 4 of them was found deviant; all 4 children were deaf owing to meningitis. Some electrodes marked as failing by E-E mapping did not cause problems during device fitting, and electrodes not usable in device fitting showed normal AEVs in 1 child. Overall, the AEVs agreed well with abnormalities in the behavioral threshold (T) and comfort (C) levels. The E-E maps provided useful clues for the audiologist in most cases. 2) Repeated E-E mapping in 2 children who displayed large fluctuations over time of T levels suggested a fluctuation in (neural) responsiveness in 1 child and new bone formation in the other. 3) Although massive phase reversals of AEVs in 2 patients deafened by otosclerosis seemed to indicate a very permeable cochlear bone, stimulation in the pseudomonopolar mode across the basal turn did not affect T levels, and affected pitch perception in only 1 patient. Deviant AEVs from abnormal cochleas should, therefore, not be interpreted too easily as an indication of an electrode failure, faulty electrode placement, or inadequate tonotopy.

Child↗

The influence of spectral composition of complex tones and of musical experience on the perceptibility of virtual pitch.

A matching paradigm was used to evaluate the influence of the spectral characteristics number, relative height, and density of harmonics on the perceptibility of the missing fundamental. Fifty-eight musicians and 58 nonmusicians were instructed to adjust mistuned sinusoids to the subjectively perceived fundamental pitches of corresponding overtone spectra. Analyses of variance were used to compare the average of absolute and relative deviations of the tunings from the highest common divisors of the complex tones. The results indicate that musical experience is the most influential single factor determining the assessment of fundamental pitch. Nevertheless, all spectral parameters significantly affect tuning performance. Systematic relative deviations (stretching/compression effects) were observed for all considered variables. An increase of the optimum subjective distance between an overtone spectrum and its corresponding fundamental was characteristic of musicians and unambiguous spectra, whereas the compression effect was typical of nonmusicians and complex tones containing spectral gaps.

Acoustic Stimulation↗

Interaction of excitatory and inhibitory frequency-receptive fields in determining fundamental frequency sensitivity of primary auditory cortex neurons in awake cats.

Harmonic complex tones produce pitch-height perception corresponding to the fundamental frequency (F0). This study investigates how the spectral cue of F0 is processed in neurons of the primary auditory cortex (A1) with sustained-response properties. We found F0-sensitive and -insensitive cells: the former discriminated between harmonics and noise, while the latter did not. F0-sensitive cells preferred F0s corresponding to the best frequency (BF) and 0.5 x BF. The F0-sensitivity to F0=0.5 x BF was preserved for missing F0, but abolished by eliminating both F0 and the second harmonic. The inhibitory subfield of the frequency-receptive field was restricted to the spectral region between the preferred harmonics in F0-sensitive cells, while it was frequency unspecific in F0-insensitive cells. We conclude that (i) A1 is well organized for discrimination between harmonics and noise; (ii) pitch-height is represented along with the tonotopic axis; (iii) all aspects of the sustained neural responses to harmonic and noise stimuli are consequences of spectral filtering; and (iv) although the observed cell behavior explains some psychophysical pitch perception behaviors, such as pitch-chroma (helical pitch perception with frequency elevation), pitch-level tolerance and adaptive behavior, F0-encoding in A1 remains at the incomplete perceptual level (dominance of the third to fifth harmonics for pitch strength is unexplainable by the cell behavior).

Acoustic Stimulation↗

The behavior of H* and L* under variations in pitch range in Dutch rising contours.

A Dutch rising intonation contour can be realized either as a rise that begins low and ends mid-to-high ("low rise") or as a rise that begins mid and ends high ("high rise"). These two contours could either be the extremes on a phonetic continuum representing a single phonological contour, for instance L* H-H%, or be realizations of two phonologically different contours, L* H-H% and H* H-H%. In order to decide between these two analyses, listeners were asked to rate stimuli with different pitch ranges on a number of semantic scales whose meanings vary with pitch range. Our hypothesis was that H-tones are higher as the pitch range increases, while L* is lower. Two preliminary experiments, in which we presented F0 contours of high rises and low rises in a number of different pitch ranges, revealed that perceived surprise, rather than perceived prominence, is an appropriate response variable for measuring pitch range perception, where increased pitch range corresponds to higher H-tones and lower L*. Subsequently, listeners were asked to indicate the degree to which each of a number of appropriately manipulated stimuli expressed "Surprise." The results lend strong support to the hypothesis that the low rise and the high rise are categorically distinct contours of Dutch, and that their first tones are L* and H*, respectively.

Adult↗

Neural response correlates of detection of monaurally and binaurally created pitches in humans.

Recent magnetoencephalography (MEG) and functional magnetic resonance imaging studies of human auditory cortex are pointing to brain areas on lateral Heschl's gyrus as the 'pitch-processing center'. Here we describe results of a combined MEG-psychophysical study designed to investigate the timing of the formation of the percept of pitch and the generality of the hypothesized 'pitch-center'. We compared the cortical and behavioral responses to Huggins pitch (HP), a stimulus requiring binaural processing to elicit a pitch percept, with responses to tones embedded in noise (TN)-perceptually similar but physically very different signals. The stimuli were crafted to separate the electrophysiological responses to onset of the pitch percept from the onset of the initial stimulus. Our results demonstrate that responses to monaural pitch stimuli are affected by cross-correlational processes in the binaural pathway. Additionally, we show that MEG illuminates processes not simply observable in behavior. Crucially, the MEG data show that, although physically disparate, both HP and TN are mapped onto similar representations by 150 ms post-onset, and provide critical new evidence that the 'pitch onset response' reflects central pitch mechanisms, in agreement with models postulating a single, central pitch extractor.

Adult↗

Perception of slow pitch and roll body tilts in bilateral labyrinthine-defective subjects.

The aim of the present study was to examine whether the perception of slow body tilts in total darkness was affected by a complete loss of vestibular function. Four blindfolded bilateral labyrinthine-defective subjects (LDs) and 12 normal subjects (Normals) were seated and immobilized with large straps against the back of a rotating L-shaped platform, and were passively displaced from the upright at 0.05 degrees x s(-1) in the pitch and roll dimensions. Subjects were asked to detect the slow change in their body orientation, by indicating as soon as possible the direction of tilt. After a brief period of practice observed for all LDs at the beginning of the session, results showed no significant difference between LDs and Normals in the mean detection threshold recorded for each direction of tilt. The mean perceptual threshold was 4.4 versus 5.1 degrees in the roll dimension, and 6.1 versus 6.1 degrees in the pitch dimension, for the LDs and Normals, respectively. These findings indicate that the accurate perception of body orientation in quasi-static conditions is mainly allowed by somatosensory information rather than by otolithic inputs.

Adult↗

Pitch interactions in the perception of isolated musical triads.

In previous work done in our laboratory, we have investigated the perceived pitch class of isolated musical triads. We have found that as the amount of musical training increased, listeners perceptions progress, from very confused percepts of pitch class, to analytic percepts corresponding to the pitch class of the highest note in the triad, and finally to synthetic percepts corresponding to the root note for the more harmonic triad types. In the present work, we used a pitch matching technique to determine the actual pitch, rather than merely the pitch class, perceived when listeners analytically "hear out" a particular note in a major triad. There was a strong tendency for the pitch of the analytically perceived note to be displaced by as much as 60 cents in the direction of the other notes in the triad. The magnitude of this effect decreased as musical training increased, and it was also affected by the relative salience of the individual triad notes. These results have implications for the mechanism of triad perception, and for claims regarding the harmonic equivalence of triad inversions.

Adolescent↗

[Discrimination of musical pitch with cochlear implants].

BACKGROUND: Numerous people with cochlear implants (CI) report difficulties in listening to music even though they understand speech quite well. One reason for this is a limited perception of pitch and timbre. In this study ability of adult CI subjects to discriminate musical pitch is investigated. PATIENTS AND METHODS: In two psychoacoustic experiments, each conducted in 10 adult CI subjects provided with MED-EL Combi 40+ cochlear implant devices and a control group of subjects with normal hearing, individual discrimination abilities for musical pitch perception were determined. To investigate the influence of the group of instruments on discrimination ability, stimuli representing four different groups of instruments were used: woodwind (clarinet), brass (trumpet), strings (violin) and keyboard instruments (piano). RESULTS: The discrimination thresholds determined varied between individual CI subjects, and on average they were significantly higher for the piano than for the other three instruments. CONCLUSIONS: The results show that in subjects with CI pitch perception differs from instrument to instrument and is in general worse than in persons with normal hearing.

Adult↗

Perception of rhythmic and sequential pitch patterns by normally hearing adults and adult cochlear implant users.

OBJECTIVE: This study compares the musical perception of 17 adult recipients of the Nucleus cochlear implant using two different formant extraction processing strategies (F0F1F2 and MPEAK). DESIGN: Over a 12 mo period, participants were alternately switched between two strategies every 3 mo. Performance was evaluated using three measures of rhythmic and sequential pitch perception. RESULTS: Three individuals performed significantly better with the MPEAK strategy on one particular rhythm task, 11 participants performed better with the MPEAK strategy on another rhythm task, and no significant differences were found between the two strategies on a sequential pitch pattern task. CONCLUSIONS: Neither strategy seems clearly superior for perception of either sequential pitch or rhythmic patterns.

Adult↗