Nicotine enhances auditory processing in healthy and normal-hearing young adult nonsmokers.

RATIONALE: Electrophysiological studies show that systemic nicotine narrows frequency receptive fields and increases gain in neural responses to characteristic frequency stimuli. We postulated that nicotine enhances related auditory processing in humans. OBJECTIVES: The main hypothesis was that nicotine improves auditory performance. A secondary hypothesis was that the degree of nicotine-induced improvement depends on the individual's baseline performance. METHODS: Young (18-27 years old), normal-hearing nonsmokers received nicotine (Nicorette gum, 6mg) or placebo gum in a single-blind, randomized, crossover design. Subjects performed four experiments involving tone-in-noise detection, temporal gap detection, spectral ripple discrimination, and selective auditory attention before and after treatment. The perceptual differences between posttreatment nicotine and placebo conditions were measured and analyzed as a function of the pre-treatment baseline performance. RESULTS: Nicotine significantly improved performance in the more difficult tasks of tone-in-noise detection and selective attention (effect size = - 0.3) but had no effect on relatively easier tasks of temporal gap detection and spectral ripple discrimination. The two tasks showing significant nicotine effects further showed no baseline-dependent improvement. CONCLUSIONS: Nicotine improves auditory performance in difficult listening situations. The present results support future investigation of nicotine effects in clinical populations with auditory processing deficits or reduced cholinergic activation.

Electro-Tactile Stimulation Enhances Cochlear-Implant Melody Recognition: Effects of Rhythm and Musical Training.

OBJECTIVES: Electro-acoustic stimulation (EAS) enhances speech and music perception in cochlear-implant (CI) users who have residual low-frequency acoustic hearing. For CI users who do not have low-frequency acoustic hearing, tactile stimulation may be used in a similar fashion as residual low-frequency acoustic hearing to enhance CI performance. Previous studies showed that electro-tactile stimulation (ETS) enhanced speech recognition in noise and tonal language perception for CI listeners. Here, we examined the effect of ETS on melody recognition in both musician and nonmusician CI users. DESIGN: Nine musician and eight nonmusician CI users were tested in a melody recognition task with or without rhythmic cues in three testing conditions: CI only (E), tactile only (T), and combined CI and tactile stimulation (ETS). RESULTS: Overall, the combined electrical and tactile stimulation enhanced the melody recognition performance in CI users by 9% points. Two additional findings were observed. First, musician CI users outperformed nonmusicians CI users in melody recognition, but the size of the enhancement effect was similar between the two groups. Second, the ETS enhancement was significantly higher with nonrhythmic melodies than rhythmic melodies in both groups. CONCLUSIONS: These findings suggest that, independent of musical experience, the size of the ETS enhancement depends on integration efficiency between tactile and auditory stimulation, and that the mechanism of the ETS enhancement is improved electric pitch perception. The present study supports the hypothesis that tactile stimulation can be used to improve pitch perception in CI users.

Tinnitus Treatment Using Noninvasive and Minimally Invasive Electric Stimulation: Experimental Design and Feasibility.

Noninvasive transcranial or minimally invasive transtympanic electric stimulation may offer a desirable treatment option for tinnitus because it can activate the deafferented auditory nerve fibers while posing little to no risk to hearing. Here, we built a flexible research interface to generate and control accurately charge-balanced current stimulation as well as a head-mounted instrument capable of holding a transtympanic electrode steady for hours. We then investigated the short-term effect of a limited set of electric stimulation parameters on tinnitus in 10 adults with chronic tinnitus. The preliminary results showed that 63% of conditions of electric stimulation produced some degree of tinnitus reduction, with total disappearance of tinnitus in six subjects in response to at least one condition. The present study also found significant side effects such as visual, tactile, and even pain sensations during electric stimulation. In addition to masking and residual inhibition, neuroplasticity is likely involved in the observed tinnitus reduction. To translate the present electric stimulation into a safe and effective tinnitus treatment option, we need to optimize stimulation parameters that activate the deafferented auditory nerve fibers and reliably suppress tinnitus, with minimal side effects and tolerable sensations. Noninvasive or minimally invasive electric stimulation can be integrated with sound therapy, invasive cochlear implants, or other forms of coordinated stimulation to provide a systematic strategy for tinnitus treatment or even a cure.

Bimodal benefits in Mandarin-speaking cochlear implant users with contralateral residual acoustic hearing.

OBJECTIVE: The present study aimed to measure bimodal benefits and probe their underlying mechanisms in Mandarin-speaking cochlear implant (CI) subjects who had contralateral residual acoustic hearing. DESIGN: The subjects recognised words or phonemes from the Mandarin Lexical Neighborhood Test in noise at a 10-dB signal-to-noise ratio (SNR) with acoustic stimulation, electric stimulation or the combined bimodal stimulation. STUDY SAMPLE: Thirteen Mandarin-speaking subjects wore a CI in one ear and had residual acoustic hearing in the contralateral ear. Six of the subjects (5.2-13.0 years) had pre-lingual onset of severe hearing loss, and seven of them (8.6-45.8 years) had post-lingual onset of severe hearing loss. RESULTS: Both groups of subjects produced a significant bimodal benefit in word recognition in noise. Consonants and tones accounted for the bimodal benefit. The bimodal integration efficiency was negatively correlated with the duration of deafness in the implanted ear for vowel recognition but positively correlated with CI or bimodal experience for consonant recognition. CONCLUSIONS: The present results support preservation of residual acoustic hearing, early cochlear implantation and continuous use of bimodal hearing for subjects who have significant residual hearing in the non-implanted ear.

Amplitude modulation reduces loudness adaptation to high-frequency tones.

Long-term loudness perception of a sound has been presumed to depend on the spatial distribution of activated auditory nerve fibers as well as their temporal firing pattern. The relative contributions of those two factors were investigated by measuring loudness adaptation to sinusoidally amplitude-modulated 12-kHz tones. The tones had a total duration of 180 s and were either unmodulated or 100%-modulated at one of three frequencies (4, 20, or 100 Hz), and additionally varied in modulation depth from 0% to 100% at the 4-Hz frequency only. Every 30 s, normal-hearing subjects estimated the loudness of one of the stimuli played at 15 dB above threshold in random order. Without any amplitude modulation, the loudness of the unmodulated tone after 180 s was only 20% of the loudness at the onset of the stimulus. Amplitude modulation systematically reduced the amount of loudness adaptation, with the 100%-modulated stimuli, regardless of modulation frequency, maintaining on average 55%-80% of the loudness at onset after 180 s. Because the present low-frequency amplitude modulation produced minimal changes in long-term spectral cues affecting the spatial distribution of excitation produced by a 12-kHz pure tone, the present result indicates that neural synchronization is critical to maintaining loudness perception over time.

Tinnitus treatment with precise and optimal electric stimulation: opportunities and challenges.

PURPOSE OF REVIEW: Electric stimulation is a potent means of neuromodulation that has been used to restore hearing and minimize tremor, but its application on tinnitus symptoms has been limited. We examine recent evidence to identify the knowledge gaps in the use of electric stimulation for tinnitus treatment. RECENT FINDINGS: Recent studies using electric stimulation to suppress tinnitus in humans are categorized according to their points of attacks. First, noninvasive, direct current stimulation uses an active electrode in the ear canal, tympanic membrane, or temporal scalp. Second, inner ear stimulation uses charge-balanced biphasic stimulation by placing an active electrode on the promontory or round window, or a cochlear implant array in the cochlea. Third, intraneural implants can provide targeted stimulation of specific sites along the auditory pathway. Although these studies demonstrated some success in tinnitus suppression, none established a link between tinnitus suppression efficacy and tinnitus-generating mechanisms. SUMMARY: Electric stimulation provides a unique opportunity to suppress tinnitus. Challenges include matching electric stimulation sites and patterns to tinnitus locus and type, meeting the oftentimes-contradictory demands between tinnitus suppression and other indications, such as speech understanding, and justifying the costs and risks of electric stimulation for tinnitus symptoms.

Development and evaluation of the Nurotron 26-electrode cochlear implant system.

Although the cochlear implant has been widely acknowledged as the most successful neural prosthesis, only a fraction of hearing-impaired people who can potentially benefit from a cochlear implant have actually received one due to its limited awareness, accessibility, and affordability. To help overcome these limitations, a 26-electrode cochlear implant has been developed to receive China's Food and Drug Administration (CFDA) approval in 2011 and Conformité Européenne (CE) Marking in 2012. The present article describes design philosophy, system specification, and technical verification of the Nurotron device, which includes advanced digital signal processing and 4 current sources with multiple amplitude resolutions that not only are compatible with perceptual capability but also allow interleaved or simultaneous stimulation. The article also presents 3-year longitudinal evaluation data from 60 human subjects who have received the Nurotron device. The objective measures show that electrode impedance decreased within the first month of device use, but was stable until a slight increase at the end of two years. The subjective loudness measures show that electric stimulation threshold was stable while the maximal comfort level increased over the 3 years. Mandarin sentence recognition increased from the pre-surgical 0%-correct score to a plateau of about 80% correct with 6-month use of the device. Both indirect and direct comparisons indicate indistinguishable performance differences between the Nurotron system and other commercially available devices. The present 26-electrode cochlear implant has already helped to lower the price of cochlear implantation in China and will likely contribute to increased cochlear implant access and success in the rest of the world. This article is part of a Special Issue entitled .

Objective assessment of spectral ripple discrimination in cochlear implant listeners using cortical evoked responses to an oddball paradigm.

Cochlear implants (CIs) can partially restore functional hearing in deaf individuals. However, multiple factors affect CI listener's speech perception, resulting in large performance differences. Non-speech based tests, such as spectral ripple discrimination, measure acoustic processing capabilities that are highly correlated with speech perception. Currently spectral ripple discrimination is measured using standard psychoacoustic methods, which require attentive listening and active response that can be difficult or even impossible in special patient populations. Here, a completely objective cortical evoked potential based method is developed and validated to assess spectral ripple discrimination in CI listeners. In 19 CI listeners, using an oddball paradigm, cortical evoked potential responses to standard and inverted spectrally rippled stimuli were measured. In the same subjects, psychoacoustic spectral ripple discrimination thresholds were also measured. A neural discrimination threshold was determined by systematically increasing the number of ripples per octave and determining the point at which there was no longer a significant difference between the evoked potential response to the standard and inverted stimuli. A correlation was found between the neural and the psychoacoustic discrimination thresholds (R2=0.60, p<0.01). This method can objectively assess CI spectral resolution performance, providing a potential tool for the evaluation and follow-up of CI listeners who have difficulty performing psychoacoustic tests, such as pediatric or new users.

Abnormal pitch perception produced by cochlear implant stimulation.

Contemporary cochlear implants with multiple electrode stimulation can produce good speech perception but poor music perception. Hindered by the lack of a gold standard to quantify electric pitch, relatively little is known about the nature and extent of the electric pitch abnormalities and their impact on cochlear implant performance. Here we overcame this obstacle by comparing acoustic and electric pitch perception in 3 unilateral cochlear-implant subjects who had functionally usable acoustic hearing throughout the audiometric frequency range in the non-implant ear. First, to establish a baseline, we measured and found slightly impaired pure tone frequency discrimination and nearly perfect melody recognition in all 3 subjects' acoustic ear. Second, using pure tones in the acoustic ear to match electric pitch induced by an intra-cochlear electrode, we found that the frequency-electrode function was not only 1-2 octaves lower, but also 2 times more compressed in frequency range than the normal cochlear frequency-place function. Third, we derived frequency difference limens in electric pitch and found that the equivalent electric frequency discrimination was 24 times worse than normal-hearing controls. These 3 abnormalities are likely a result of a combination of broad electric field, distant intra-cochlear electrode placement, and non-uniform spiral ganglion cell distribution and survival, all of which are inherent to the electrode-nerve interface in contemporary cochlear implants. Previous studies emphasized on the "mean" shape of the frequency-electrode function, but the present study indicates that the large "variance" of this function, reflecting poor electric pitch discriminability, is the main factor limiting contemporary cochlear implant performance.

Cochlear implant artifact attenuation in late auditory evoked potentials: a single channel approach.

Recent evidence suggests that late auditory evoked potentials (LAEP) provide a useful objective metric of performance in cochlear implant (CI) subjects. However, the CI produces a large electrical artifact that contaminates LAEP recordings and confounds their interpretation. Independent component analysis (ICA) has been used in combination with multi-channel recordings to effectively remove the artifact. The applicability of the ICA approach is limited when only single channel data are needed or available, as is often the case in both clinical and research settings. Here we developed a single-channel, high sample rate (125 kHz), and high bandwidth (0-100 kHz) acquisition system to reduce the CI stimulation artifact. We identified two different artifacts in the recording: 1) a high frequency artifact reflecting the stimulation pulse rate, and 2) a direct current (DC, or pedestal) artifact that showed a non-linear time varying relationship to pulse amplitude. This relationship was well described by a bivariate polynomial. The high frequency artifact was completely attenuated by a 35 Hz low-pass filter for all subjects (n = 22). The DC artifact could be caused by an impedance mismatch. For 27% of subjects tested, no DC artifact was observed when electrode impedances were balanced to within 1 kΩ. For the remaining 73% of subjects, the pulse amplitude was used to estimate and then attenuate the DC artifact. Where measurements of pulse amplitude were not available (as with standard low sample rate systems), the DC artifact could be estimated from the stimulus envelope. The present artifact removal approach allows accurate measurement of LAEPs from CI subjects from single channel recordings, increasing their feasibility and utility as an accessible objective measure of CI function.

Loudness adaptation accompanying ribbon synapse and auditory nerve disorders.

Abnormal auditory adaptation is a standard clinical tool for diagnosing auditory nerve disorders due to acoustic neuromas. In the present study we investigated auditory adaptation in auditory neuropathy owing to disordered function of inner hair cell ribbon synapses (temperature-sensitive auditory neuropathy) or auditory nerve fibres. Subjects were tested when afebrile for (i) psychophysical loudness adaptation to comfortably-loud sustained tones; and (ii) physiological adaptation of auditory brainstem responses to clicks as a function of their position in brief 20-click stimulus trains (#1, 2, 3 … 20). Results were compared with normal hearing listeners and other forms of hearing impairment. Subjects with ribbon synapse disorder had abnormally increased magnitude of loudness adaptation to both low (250 Hz) and high (8000 Hz) frequency tones. Subjects with auditory nerve disorders had normal loudness adaptation to low frequency tones; all but one had abnormal adaptation to high frequency tones. Adaptation was both more rapid and of greater magnitude in ribbon synapse than in auditory nerve disorders. Auditory brainstem response measures of adaptation in ribbon synapse disorder showed Wave V to the first click in the train to be abnormal both in latency and amplitude, and these abnormalities increased in magnitude or Wave V was absent to subsequent clicks. In contrast, auditory brainstem responses in four of the five subjects with neural disorders were absent to every click in the train. The fifth subject had normal latency and abnormally reduced amplitude of Wave V to the first click and abnormal or absent responses to subsequent clicks. Thus, dysfunction of both synaptic transmission and auditory neural function can be associated with abnormal loudness adaptation and the magnitude of the adaptation is significantly greater with ribbon synapse than neural disorders.

Rate and onset cues can improve cochlear implant synthetic vowel recognition in noise.

Understanding speech-in-noise is difficult for most cochlear implant (CI) users. Speech-in-noise segregation cues are well understood for acoustic hearing but not for electric hearing. This study investigated the effects of stimulation rate and onset delay on synthetic vowel-in-noise recognition in CI subjects. In experiment I, synthetic vowels were presented at 50, 145, or 795 pulse/s and noise at the same three rates, yielding nine combinations. Recognition improved significantly if the noise had a lower rate than the vowel, suggesting that listeners can use temporal gaps in the noise to detect a synthetic vowel. This hypothesis is supported by accurate prediction of synthetic vowel recognition using a temporal integration window model. Using lower rates a similar trend was observed in normal hearing subjects. Experiment II found that for CI subjects, a vowel onset delay improved performance if the noise had a lower or higher rate than the synthetic vowel. These results show that differing rates or onset times can improve synthetic vowel-in-noise recognition, indicating a need to develop speech processing strategies that encode or emphasize these cues.

Temporary suppression of tinnitus by modulated sounds.

Despite high prevalence of tinnitus and its impact on quality life, there is no cure for tinnitus at present. Here, we report an effective means to temporarily suppress tinnitus by amplitude- and frequency-modulated tones. We systematically explored the interaction between subjective tinnitus and 17 external sounds in 20 chronic tinnitus sufferers. The external sounds included traditionally used unmodulated stimuli such as pure tones and white noise and dynamically modulated stimuli known to produce sustained neural synchrony in the central auditory pathway. All external sounds were presented in a random order to all subjects and at a loudness level that was just below tinnitus loudness. We found some tinnitus suppression in terms of reduced loudness by at least one of the 17 stimuli in 90% of the subjects, with the greatest suppression by amplitude-modulated tones with carrier frequencies near the tinnitus pitch for tinnitus sufferers with relatively normal loudness growth. Our results suggest that, in addition to a traditional masking approach using unmodulated pure tones and white noise, modulated sounds should be used for tinnitus suppression because they may be more effective in reducing hyperactive neural activities associated with tinnitus. The long-term effects of the modulated sounds on tinnitus and the underlying mechanisms remain to be investigated.

Towards a closed-loop cochlear implant system: application of embedded monitoring of peripheral and central neural activity.

Although the cochlear implant (CI) is widely considered the most successful neural prosthesis, it is essentially an open-loop system that requires extensive initial fitting and frequent tuning to maintain a high, but not necessarily optimal, level of performance. Two developments in neuroscience and neuroengineering now make it feasible to design a closed-loop CI. One development is the recording and interpretation of evoked potentials (EPs) from the peripheral to the central nervous system. The other is the embedded hardware and software of a modern CI that allows recording of EPs. We review EPs that are pertinent to behavioral functions from simple signal detection and loudness growth to speech discrimination and recognition. We also describe signal processing algorithms used for electric artifact reduction and cancellation, critical to the recording of electric EPs. We then present a conceptual design for a closed-loop CI that utilizes in an innovative way the embedded implant receiver and stimulators to record short latency compound action potentials ( ~1 ms), auditory brainstem responses (1-10 ms) and mid-to-late cortical potentials (20-300 ms). We compare EPs recorded using the CI to EPs obtained using standard scalp electrodes recording techniques. Future applications and capabilities are discussed in terms of the development of a new generation of closed-loop CIs and other neural prostheses.

Cochlear-implant spatial selectivity with monopolar, bipolar and tripolar stimulation.

Sharp spatial selectivity is critical to auditory performance, particularly in pitch-related tasks. Most contemporary cochlear implants have employed monopolar stimulation that produces broad electric fields, which presumably contribute to poor pitch and pitch-related performance by implant users. Bipolar or tripolar stimulation can generate focused electric fields but requires higher current to reach threshold and, more interestingly, has not produced any apparent improvement in cochlear-implant performance. The present study addressed this dilemma by measuring psychophysical and physiological spatial selectivity with both broad and focused stimulations in the same cohort of subjects. Different current levels were adjusted by systematically measuring loudness growth for each stimulus, each stimulation mode, and in each subject. Both psychophysical and physiological measures showed that, although focused stimulation produced significantly sharper spatial tuning than monopolar stimulation, it could shift the tuning position or even split the tuning tips. The altered tuning with focused stimulation is interpreted as a result of poor electrode-to-neuron interface in the cochlea, and is suggested to be mainly responsible for the lack of consistent improvement in implant performance. A linear model could satisfactorily quantify the psychophysical and physiological data and derive the tuning width. Significant correlation was found between the individual physiological and psychophysical tuning widths, and the correlation was improved by log-linearly transforming the physiological data to predict the psychophysical data. Because the physiological measure took only one-tenth of the time of the psychophysical measure, the present model is of high clinical significance in terms of predicting and improving cochlear-implant performance.

Combined spectral and temporal enhancement to improve cochlear-implant speech perception.

The present study examined the effect of combined spectral and temporal enhancement on speech recognition by cochlear-implant (CI) users in quiet and in noise. The spectral enhancement was achieved by expanding the short-term Fourier amplitudes in the input signal. Additionally, a variation of the Transient Emphasis Spectral Maxima (TESM) strategy was applied to enhance the short-duration consonant cues that are otherwise suppressed when processed with spectral expansion. Nine CI users were tested on phoneme recognition tasks and ten CI users were tested on sentence recognition tasks both in quiet and in steady, speech-spectrum-shaped noise. Vowel and consonant recognition in noise were significantly improved with spectral expansion combined with TESM. Sentence recognition improved with both spectral expansion and spectral expansion combined with TESM. The amount of improvement varied with individual CI users. Overall the present results suggest that customized processing is needed to optimize performance according to not only individual users but also listening conditions.

Fundamental frequency is critical to speech perception in noise in combined acoustic and electric hearing.

Cochlear implant (CI) users have been shown to benefit from residual low-frequency hearing, specifically in pitch related tasks. It remains unclear whether this benefit is dependent on fundamental frequency (F0) or other acoustic cues. Three experiments were conducted to determine the role of F0, as well as its frequency modulated (FM) and amplitude modulated (AM) components, in speech recognition with a competing voice. In simulated CI listeners, the signal-to-noise ratio was varied to estimate the 50% correct response. Simulation results showed that the F0 cue contributes to a significant proportion of the benefit seen with combined acoustic and electric hearing, and additionally that this benefit is due to the FM rather than the AM component. In actual CI users, sentence recognition scores were collected with either the full F0 cue containing both the FM and AM components or the 500-Hz low-pass speech cue containing the F0 and additional harmonics. The F0 cue provided a benefit similar to the low-pass cue for speech in noise, but not in quiet. Poorer CI users benefited more from the F0 cue than better users. These findings suggest that F0 is critical to improving speech perception in noise in combined acoustic and electric hearing.

Ipsilateral masking between acoustic and electric stimulations.

Residual acoustic hearing can be preserved in the same ear following cochlear implantation with minimally traumatic surgical techniques and short-electrode arrays. The combined electric-acoustic stimulation significantly improves cochlear implant performance, particularly speech recognition in noise. The present study measures simultaneous masking by electric pulses on acoustic pure tones, or vice versa, to investigate electric-acoustic interactions and their underlying psychophysical mechanisms. Six subjects, with acoustic hearing preserved at low frequencies in their implanted ear, participated in the study. One subject had a fully inserted 24 mm Nucleus Freedom array and five subjects had Iowa/Nucleus hybrid implants that were only 10 mm in length. Electric masking data of the long-electrode subject showed that stimulation from the most apical electrodes produced threshold elevations over 10 dB for 500, 625, and 750 Hz probe tones, but no elevation for 125 and 250 Hz tones. On the contrary, electric stimulation did not produce any electric masking in the short-electrode subjects. In the acoustic masking experiment, 125-750 Hz pure tones were used to acoustically mask electric stimulation. The acoustic masking results showed that, independent of pure tone frequency, both long- and short-electrode subjects showed threshold elevations at apical and basal electrodes. The present results can be interpreted in terms of underlying physiological mechanisms related to either place-dependent peripheral masking or place-independent central masking.

Binaural unmasking with multiple adjacent masking electrodes in bilateral cochlear implant users.

Bilateral cochlear implant (BiCI) users gain an advantage in noisy situations from a second implant, but their bilateral performance falls short of normal hearing listeners. Channel interactions due to overlapping electrical fields between electrodes can impair speech perception, but its role in limiting binaural hearing performance has not been well characterized. To address the issue, binaural masking level differences (BMLD) for a 125 Hz tone in narrowband noise were measured using a pair of pitch-matched electrodes while simultaneously presenting the same masking noise to adjacent electrodes, representing a more realistic stimulation condition compared to prior studies that used only a single electrode pair. For five subjects, BMLDs averaged 8.9 ± 1.0 dB (mean ± s.e.) in single electrode pairs but dropped to 2.1 ± 0.4 dB when presenting noise on adjacent masking electrodes, demonstrating a negative impact of the additional maskers. Removing the masking noise from only the pitch-matched electrode pair not only lowered thresholds but also resulted in smaller BMLDs. The degree of channel interaction estimated from auditory nerve evoked potentials in three subjects was significantly and negatively correlated with BMLD. The data suggest that if the amount of channel interactions can be reduced, BiCI users may experience some performance improvements related to binaural hearing.

Tinnitus suppression by low-rate electric stimulation and its electrophysiological mechanisms.

Tinnitus is a phantom sensation of sound in the absence of external stimulation. However, external stimulation, particularly electric stimulation via a cochlear implant, has been shown to suppress tinnitus. Different from traditional methods of delivering speech sounds or high-rate (>2000 Hz) stimulation, the present study found a unique unilaterally-deafened cochlear implant subject whose tinnitus was completely suppressed by a low-rate (<100 Hz) stimulus, delivered at a level softer than tinnitus to the apical part of the cochlea. Taking advantage of this novel finding, the present study compared both event-related and spontaneous cortical activities in the same subject between the tinnitus-present and tinnitus-suppressed states. Compared with the results obtained in the tinnitus-present state, the low-rate stimulus reduced cortical N100 potentials while increasing the spontaneous alpha power in the auditory cortex. These results are consistent with previous neurophysiological studies employing subjects with and without tinnitus and shed light on both tinnitus mechanism and treatment.