Although there has been a growing body of literature showing the neural correlation of forward masking caused by a pure tone masker in the auditory neurons, relative few studies have addressed the description of how the forward masking caused by a noise burst, especially a sequence of noise burst, is transformed into neuronal representation in the central auditory system. Using a noise forward masking paradigm under free field stimuli conditions, this in vivo study was devoted to exploring it in the inferior collicular (IC) neurons of the mouse (Mus musculus KM). A total of 96 IC neurons were recorded. Rate-intensity functions (RIFs) with and without the presentation of masker, sustained noise burst (SNB) or segmental noise burst (SGNB), were measured in 51 neurons. We found that the relative masker intensities were distributed over a wide range between 21 dB below the minimum threshold (MT) and 19 dB above the MT of the corresponding probe tone. The masking effect of the SGNB on firing rate in nearly half of neurons (type I, 45.10%) was stronger than that of the SNB (P<0.001), whereas in a smaller fraction of neurons (type III, 17.65%), it was weaker than that of the SNB (P<0.001). There was no significant difference in masking effect between the SNB and SGNB in type II neurons (37.25%, P>0.05). Irrespective of type I or type III neurons, the inhibitory effects of both kinds of maskers were all greater at lower probe intensities but decreased significantly with the increase of probe intensity (P<0.001). Interestingly, as the probe intensity increased, the difference of masking effect between the SNB and SGNB disappeared (P>0.05). In addition, we observed that temporal masking pattern could be transformed when the masker was changed from the SNB to SGNB. The main type of this transformation was from early-inhibition to proportional-inhibition pattern (53.85%, 7/13). Our data provide the evidence that the inhibitory effects of these two maskers have differential weights over time and intensity domains of the IC neurons responding to a pure tone. This suggests that the forward masking of noise is by no means the source of simply suppression in neuronal firing rate. There might be a few of active neural modulating ways in which the coding of temporal acoustical information can be operated.
Acoustic Stimulation ; Animals ; Female ; Inferior Colliculi ; physiology ; Male ; Mice ; Neurons ; physiology ; Noise ; Perceptual Masking ; physiology

Masking therapy can make patients accustom to tinnitus. This therapy is safe and easy to implement, so that it has become a widely used treatment of curing tinnitus. According to surveys of tinnitus sounds, cicada sound is one of the most usual tinnituses. Meanwhile, we have not hitherto found published papers concerning how to synthesize cicada sound and to use it to ameliorate tinnitus. Inspired by the human acoustics theory, we proposed a method to synthesize medical masking sound and to realize the diversity by illustrating the process of synthesizing various cicada sounds. In addition, energy attenuation problem in spectrum shifting process has been successfully solved. Simulation results indicated that the proposed method achieved decent results and would have practical value for the future applications.
Acoustic Stimulation ; Animals ; Computer Simulation ; Hemiptera ; Humans ; Perceptual Masking ; physiology ; Sound ; Tinnitus ; therapy ; Vocalization, Animal

OBJECTIVETry to observe the plasticity of neuron in primary cortex of rat evoked by conditioned stimulus of different sound level.

METHODSApplying conventional electrophysiological technique of extracellular recording to investigate the plasticity of characteristic frequency (CF) and frequency turning curve (FIC) of neurons in rat auditory cortex (AC) by determining CF shifts of neurons caused by sound stimulus of different sound level.

RESULTSWhen the frequency difference between conditioned stimulus (CS) frequency and the CF of neuron was in 1.0 kHz, the plasticity of CF induced by CS was associated with sound level. The probability of the plasticity of CF evoked by CS of higher sound lever was more than the lower. And the probability was dependent on frequency turning curve (FTC) and almost independent on the sound level of conditioned signal.

CONCLUSIONSound level of conditioned stimulus differs the plasticity of characteristic frequency of neurons in rat auditory cortex.

Acoustic Stimulation ; Animals ; Auditory Cortex ; cytology ; Auditory Perception ; physiology ; Conditioning, Classical ; physiology ; Female ; Male ; Neuronal Plasticity ; physiology ; Neurons ; physiology ; Perceptual Masking ; Rats ; Rats, Sprague-Dawley ; Sound

Temporal features of sound convey information vital for behaviors as diverse as speech recognition by human and echolocation by bats. However, auditory stimuli presented in temporal proximity might interfere with each other. Although much progress has been made in the description of this phenomenon from psychophysical studies, the neural mechanism responsible for its formation at central auditory structures especially at the inferior colliculus (IC), a midbrain auditory nucleus which practically receives massive bilateral projections from all the major auditory structures in the brainstem, remains unclear. This study was designed to investigate it in vivo by using electrophysiological recording from the inferior collicular neurons of the big brown bat, Eptesicus fuscus. In our results, the responses of 12 (38%, n= 31) neurons to the test sound (leading sound) were obviously inhibited by the masker (lagging sound). The inhibitory effects in these neurons were correlated with the inter-stimulus level difference (SLD) and the inter-stimulus onset asynchrony (SOA) interval. The strength of backward masking increased with the masker intensity increasing, the test sound intensity decreasing and the SOA interval shortening. There were no obvious effects of backward masking on the responses of many other neurons (52%, 16/31), and yet in a part of these neurons, the neural inhibition of responses to the test sound was observed at the special SLD and the special SOA intervals. Moreover, few of the 31 sampled IC neurons (10%, 3/31) displayed facilitating responses to the test sound at the special SLD and the special SOA intervals. These data demonstrate that a lot of IC neurons are involved in the generation of the backward masking of acoustical perception. It is conjectured that the temporal dynamic integration between the leading inhibitory inputs evoked by the masker sound and the excitatory inputs evoked by the test sound might play a key role in shaping the acoustical response characteristics of the IC neurons.
Acoustic Stimulation ; Animals ; Auditory Perception ; physiology ; Chiroptera ; physiology ; Echolocation ; physiology ; Evoked Potentials, Auditory ; Inferior Colliculi ; cytology ; physiology ; Male ; Neurons ; physiology ; Perceptual Masking ; physiology

OBJECTIVE: To investigate the relationship between minimum contralateral masking level (MCML) and pure tone threshold of the masking ears by the same frequency tone masking test. METHODS: The pure tone thresholds of 30 subjects (60 ears) were measured by pure tone audiometry and MCML was obtained by means of the same frequency tone masking test. RESULTS: When the stimulus was at the threshold of masked ears, the differences between MCML and pure tone threshold of masking ears were among 0-30 dBHL. 82.4 percent of results showed the differences not higher than 10 dBHL, 97.1 percent of results showed the differences not higher than 15 dBHL. When the stimulus was at 10 dBHL above the threshold of masked ears, the differences between MCML and pure tone threshold of masking ears were among 0-35 dBHL. 90.5 percent of results showed the differences not higher than 25 dBHL, 98.1 percent of results showed the differences not higher than 30 dBHL. CONCLUSION The real thresholds can be deduced correctly by the same frequency tone masking test.
Acoustic Stimulation/methods* ; Adult ; Audiometry, Pure-Tone/methods* ; Auditory Perception/physiology* ; Auditory Threshold ; Female ; Forensic Medicine/methods* ; Hearing Tests/methods* ; Humans ; Male ; Perceptual Masking

OBJECTIVE: To study the long-term rehabilitation effects for treating tinnitus by tinnitus masking combined with counseling. METHOD: Complete the tinnitus handicap inventory(THI) for participants before treatment and after six months, 1 year, 2 years, 3 years. RESULT: Eighty-six tinnitus patients participated. Nine participants and sixteen, twenty-six, sixteen participants drop-up during the follow up after half-year, 1 year, 2 years, 3 years separately. The percentage of participants whose THI score decreased more than or equal to 20 are 66%, 56%, 40%, 48% after half year, 1 year, 2 years, 3 years respectively. CONCLUSION The tinnitus related handicap improved by tinnitus masking combined with counseling after 1 year. The drop-out rate was increase after follow-up 1 year. The long-term rehabilitation effects for tinnitus treatment is still needed.
Adolescent ; Adult ; Aged ; Counseling ; Female ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Perceptual Masking ; Tinnitus ; psychology ; rehabilitation ; therapy ; Treatment Outcome ; Young Adult

OBJECTIVE: To observe the relationship between the tinnitus masking curve and the effect of masking therapy, so as to select an effective treatment method. METHOD: Detect 108 (137 ear) tinnitus patients, and all the patients accept masking therapy. RESULT: The type I and III of the tinnitus masking curve were the highest percentage. In residual inhibition test type I and III had the highest positive rate, and masking therapy was the best treatment for type I and III. The residual inhibition test was positive correlation to the effect of masking therapy. CONCLUSION The effectiveness of different types of masking curve are different in patients with the treatment of masking, patients should be provided with personalized treatment on masking curve and residual inhibition test.
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Female ; Hearing Aids ; Humans ; Male ; Middle Aged ; Perceptual Masking ; Tinnitus ; therapy ; Treatment Outcome ; Young Adult