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

OBJECTIVEA pilot study found the masking level difference (MLD) normal value of Chinese aged from 10 to 40, served to clinical practice.

METHODSeventy-three normal persons with hearing threshold < 20 dB and no disorder of otology were divided into three groups: classified 10-20 age as A group, 21-30 age as B group, 31-40 age as C group. MLD of age, gender and race were determined by the audiometer with dual channel by playing audio test disc. Same tests were compared with English language.

RESULTSThe mean value of MLD in Chinese was (11.1 ± 3.4) dB and the 95% normal reference values were between 4.4 to 17.8 dB . There was no difference in term of gender. The value of MLD increased with age. In the term of language, foreign showed high value of MLD than that of Chinese.

CONCLUSIONSThe measuring of MLD depends on age and language but not depends on gender. The normal threshold of MLD depends on age and language should be measured when normal values were applied to assess MLD in clinical practice.

Asian Continental Ancestry Group ; Audiometry ; Auditory Threshold ; China ; Hearing Tests ; Humans ; Language ; Otolaryngology ; Perceptual Masking ; Pilot Projects ; Reference Values

OBJECTIVETo study the characteristic of the cochlear hydrops analysis masking procedure (CHAMP) in normal adults, and to evaluate the diagnostic values of its parameters for membranous labyrinth hydrops.

METHODSTwenty otologically normal adults were recruited (male:female = 10:10), and their auditory brainstem responses (ABR) were obtained to six stimulus conditions using Bio-logic auditory evoked potential system: clicks presented alone (unmasked condition) and clicks presented with ipsilateral pink noise high-pass filtered at 8, 4, 2, 1, and 0.5 kHz respectively.

RESULTSThe wave V latency of ABR to the high-pass masking pink noise clicks were longer than ABR to clicks alone. The latency delays of wave V for clicks presented with ipsilateral pink noise high-pass filtered at 8, 4, 2, 1, and 0.5 kHz compared to clicks alone were (0.30 ± 0.18), (0.97 ± 0.43), (1.65 ± 0.64), (3.21 ± 0.56), (4.66 ± 0.37) ms respectively. The complex amplitude ratio between ABR to click + 0.5 kHz high-pass noise and click alone was 0.95 ± 0.11.

CONCLUSIONSCHAMP is a promising diagnostic method for membranous labyrinth hydrops, and the latency delay of wave V might be used as the normal criterion. The specificity of the complex amplitude ratio need further evaluation in clinical work.

Adolescent ; Adult ; Endolymphatic Hydrops ; diagnosis ; physiopathology ; Evoked Potentials, Auditory, Brain Stem ; Female ; Humans ; Male ; Noise ; Perceptual Masking ; Young Adult

OBJECTIVETo compare acoustically evoked short latency negative responses (ASNR) elicited from normal and profound hearing loss guinea pig ears and to confirm their vestibular nuclei origination.

METHODSForty healthy guinea pigs were employed in the experiment, which were randomly divided into the control group (8 subjects, 16 ears), the masking group (16 subjects, 32 ears) and the deafened group (16 subjects, 32 ears). Air conductive white noise was chosen for masking. Masking dilemma was avoidable by an appropriate 15 dB gap between stimulus and masking sound. Both the masking group and the deafened group were further divided into ASNR group and non-ASNR group based on the presence of ASNR. Electrolytic lesion was conducted to the vestibular nuclei, followed by ABR/ASNR recording. The lesioned brainstem slices were microscopically verified.

RESULTSIn the masking group, ASNR were present in 24 ears (75.0%, 24/32) and 12 ears (46.2%, 12/26) in deafened group, showing statistically higher presence rate for masking group (χ(2)=5.07, P=0.024). There were no significant differences for the ASNR threshold and latency between the masking ASNR group and the deafened ASNR group. For the two ASNR groups, electrolytic destruction to the vestibular nuclei subsequently eliminated the ASNR. Brainstem slice proved the accurate sites of electrolytic lesion.

CONCLUSIONModerate white noise masking prevents hearing system potential overlap without affecting vestibular system, therefore, ASNR is successfully elicited in normal guinea pigs. Both ASNRs from normal and deafened guinea pigs are of similar natures and origination from, the vestibular nuclei.

Animals ; Deafness ; physiopathology ; Evoked Potentials, Auditory, Brain Stem ; Guinea Pigs ; Hearing ; physiology ; Hearing Tests ; Noise ; Perceptual Masking ; Reaction Time ; Sound ; Vestibular Nuclei ; physiology

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

OBJECTIVETo undergo tinnitus evaluation test and masking therapy of subject tinnitus associated with sensorineural hearing loss as a reference for diagnosis and guiding masking therapy.

METHODSThe 66 patients with subject tinnitus were diagnosed as sensorineural hearing loss. Sixty-six patients divide into three groups according to the results of pure tone audiometry, including steep drop type in 28 patients, slow drop type in 20 patients, and flat type in 18 patients. All the patients underwent tinnitus evaluation tests (pitch matching, intensity matching, tinnitus masking curves, residual inhibition) and masking therapy.

RESULTSTinnitus with steep drop type manifest was as low intensity [average intensity (5.7 +/- 2.9) dB (x(-) +/- s)] and high frequency (median with 4750 Hz). Residual inhibition was almost positive, but was usually consistent with convergence and congruence tinnitus masking curves. Masking therapy had better effect in the treatment of this type of tinnitus (effective rate 89.3%). Tinnitus with slow drop type manifest was as low intensity [average intensity: (6.2 +/- 4.8) dB] and high frequency (median: 4050 Hz). The distribution of residual inhibition and tinnitus masking curves had no obviously characteristics. The effective rate of masking therapy of this type of tinnitus (55.0%) was higher than tinnitus with flat type but low than that of tinnitus with steep drop type. The intensity of tinnitus with flat type [average intensity: (9.2 +/- 5.0) dB] was higher than that of the previous groups. The distribution of frequency of this type had no obviously characteristics. The residual inhibition was almost negative, and was usually consistent with divergence and persistence tinnitus masking curves. Masking therapy had unsatisfactory curative effect in the treatment of this type of tinnitus (effective rate 11.1%). The effective rate of masking therapy was significant differences among the three groups (chi(2) = 9.127, P < 0.05).

CONCLUSIONSFor the tinnitus patients with steep drop type audiometric curve, they are recommended masking therapy. For the tinnitus patients with slow drop type audiometric curve, masking therapy may be attempted to perform. For the tinnitus patients with flat type audiometric curve, they do not recommend the masking therapy.

Adolescent ; Adult ; Aged ; Audiometry, Pure-Tone ; Female ; Hearing Loss, Sensorineural ; diagnosis ; physiopathology ; therapy ; Humans ; Male ; Middle Aged ; Perceptual Masking ; Tinnitus ; diagnosis ; physiopathology ; therapy ; Young Adult

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 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