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The present study examined the effects of steep high-frequency sensorineural hearing loss (SHF-SNHL) on speech recognition using acoustic temporal fine structure (TFS) in the low-frequency region where the absolute thresholds appeared to be normal. In total, 28 participants with SHF-SNHL were assigned to 3 groups according to the cut-off frequency (1, 2, and 4 kHz, respectively) of their pure-tone absolute thresholds. Fourteen age-matched normal-hearing (NH) individuals were enrolled as controls. For each Mandarin sentence, the acoustic TFS in 10 frequency bands (each 3-ERB wide) was extracted using the Hilbert transform and was further lowpass filtered at 1, 2, and 4 kHz. Speech recognition scores were compared among the NH and 1-, 2-, and 4-kHz SHF-SNHL groups using stimuli with varying bandwidths. Results showed that speech recognition with the same TFS-speech stimulus bandwidth differed significantly in groups and filtering conditions. Sentence recognition in quiet conditions was better than that in noise. Compared with the NH participants, nearly all the SHF-SNHL participants showed significantly poorer sentence recognition within their frequency regions with “normal hearing” (defined clinically by normal absolute thresholds) in both quiet and noisy conditions. These may result from disrupted auditory nerve function in the “normal hearing” low-frequency regions.

To evaluate the potential ototoxicity of high-dose celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor.Prospective animal study.Laboratory.Twenty adult male Sprague Dawley rats were divided into 2 groups for hearing and tinnitus tests, respectively. The auditory brain-stem response (ABR) and the gap prepulse inhibition of acoustic startle (GPIAS) were used as indicators of hearing loss and tinnitus, respectively, and were measured before and at 2, 4, 6, 8, 12, 24, and 48 hours after administration of celecoxib (2 g/kg) via gavage.ABR threshold and wave III latencies did not increase significantly at any frequency following celecoxib administration, at any time point (P.05). GPIAS remained below 30% after celecoxib, from a baseline of 20.03% ± 3.62%; no change was significant.High-dose celecoxib (2 g/kg), a selective COX-2 inhibitor, did not cause hearing loss or tinnitus in Sprague Dawley rats within 48 hours of administration. Further studies are needed to explore the roles played by COX-related mechanisms when nonselective COX inhibitors induce ototoxicity.

Purpose Systemic steroid therapy (SST) for sudden sensorineural hearing loss (SSNHL) is considered the only effective treatment, but the results are not satisfactory in clinical practice. Intratympanic steroid (ITS) treatment has been adopted as a salvage treatment for patients in whom previous SST failed. However, the uncertain results of ITS treatment as a salvage treatment present patients with the dilemma of accepting or refusing ITS treatment. The goal of this study was to review relevant studies and analyze the pooled data to determine whether ITS treatment is effective for SSNHL after the failure of SST. Methods A literature search of the PubMed, Embase, and Cochrane databases to May 2014 was performed without restrictions regarding the language of publication. The studies were screened after reading the abstract and full text. Only prospective, randomized, controlled trials that evaluated the effect of ITS therapy on SSNHL adult patients after SST failed were included in the meta-analysis. Improvements in pure tone averages and the number of patients with no improvement were extracted and entered into RevMan software to meta-analyze the overall effect of ITS on SSNHL after SST failed. Findings A total of 543 studies were identified, and 41 of these studies were found to be eligible and related to ITS therapy after SST failed. Ultimately, 5 randomized, controlled trials containing data from 102 patients in the ITS group and 101 control subject were included. The pooled results revealed that ITS therapy was able to improve the hearing levels of SSNHL patients who had responded poorly to SST. Implications ITS therapy might be an effective approach to the treatment of SSNHL after SST fails.

The aim of the present study was to explore the demographic, clinical, and pathogenetic features; and treatment outcomes of patients with benign paroxysmal positional vertigo (BPPV) who were negative upon positional testing at their first referral. A total of 133 patients presented with histories of BPPV but were negative, in our hands, upon positional testing. Patients were told to cease taking vestibular suppressant medication (if any) and were to return for re-examination when positional vertigo symptoms recurred. If BPPV was diagnosed, the appropriate repositioning maneuver was applied and patients were re-examined weekly until the characteristic nystagmus and vertigo disappeared. Follow-up was performed 1 week, 4 weeks, 3 months, 6 months, and 1 year after diagnosis. The 133 patients were compared with a group of 250 patients with typical BPPV. Sixty-five of the 133 patients (termed the n-BPPV group) were subsequently identified with typical BPPV. Such diagnoses were made within 10 days of the first referral in 37 (56.9%) cases. Patients of the n-BPPV group had a longer duration of the last episode of vertigo than did others (39.7 ± 38.4 vs. 26.1 ± 36.7 days, p < 0.001), and a higher proportion used vestibular suppressant medication prior to first referral (75.4 vs. 54.8%, p = 0.003). The n-BPPV and typical BPPV patients responded similarly to treatment and exhibited similar recurrence rates. BPPV patients who were negative upon positional testing at first referral were quite common, accounting for 26% of all typical BPPV patients. No significant difference in either treatment outcome or recurrence rate was evident between n-BPPV and typical BPPV positions. Positional vertigo and nystagmus are not always present as BPPV progresses.

Objective. In this study, we aimed to identify mt3243A > G mutation carriers in a group of Chinese elderly type 2 diabetic patients by a rapid and noninvasive diagnostic system. Methods. DNA was extracted from blood, saliva, and urine sediment samples. The mutation screening and quantitation of heteroplasmy were performed by high-resolution melting (HRM) curve and pyrosequencing, respectively. Patients with mt3243A > G mutation underwent a detailed audiometric, ophthalmologic, neurological, and cardiac examination. Results. Two patients (2/1041) carrying the mt3243A > G mutation were detected among all type 2 diabetic patients. In patient 1, the heteroplasmy was 0.8%, 2.8%, and 14.7% in peripheral blood leukocytes, saliva, and urine sediment, respectively. In patient 2, the heteroplasmy was 5.3%, 8.4%, and 37.7% in peripheral blood leukocytes, saliva, and urine sediment, respectively. Both of the two patients showed hearing impairment. Abnormal ophthalmologic conditions and hyperintensity on T2-weighted magnetic resonance images were showed in patient 1. Conclusion. The occurrence of mt3243 A > G mutation was 0.2% in Chinese elderly type 2 diabetic patients. Moreover, detection of mt3243 A > G mutation in urine sediment with high-resolution melting (HRM) curve and pyrosequencing is feasible in molecular genetic diagnosis.

Acoustic temporal envelope (E) cues containing speech information are distributed across the frequency spectrum. To investigate the relative weight of E cues in different frequency regions for Mandarin sentence recognition, E information was extracted from 30 contiguous bands across the range of 80–7,562 Hz using Hilbert decomposition and then allocated to five frequency regions. Recognition scores were obtained with acoustic E cues from 1 or 2 random regions from 40 normal-hearing listeners. While the recognition scores ranged from 8.2% to 16.3% when E information from only one region was available, the scores ranged from 57.9% to 87.7% when E information from two frequency regions was presented, suggesting a synergistic effect among the temporal E cues in different frequency regions. Next, the relative contributions of the E information from the five frequency regions to sentence perception were computed using a least-squares approach. The results demonstrated that, for Mandarin Chinese, a tonal language, the temporal E cues of Frequency Region 1 (80–502 Hz) and Region 3 (1,022–1,913 Hz) contributed more to the intelligence of sentence recognition than other regions, particularly the region of 80–502 Hz, which contained fundamental frequency (F0) information.

This study explored whether the time-compressed speech perception varied with the degree of hearing loss in high-frequency sensorineural hearing loss (HF SNHL) individuals. 65 HF SNHL individuals with different cutoff frequencies were recruited and further divided into mildly, moderately, and/or severely affected subgroups in terms of the averaged thresholds of all frequencies exhibiting hearing loss. Time-compressed speech recognition scores under both quiet and noisy conditions and gap detection thresholds within low frequencies that had normal thresholds were obtained from all patients and compared with data from 11 age-matched individuals with normal hearing threshold at all frequencies. Correlations of the time-compressed speech recognition scores with the extents of HF SNHL and with the 1 kHz gap detection thresholds were studied across all participants. We found that the time-compressed speech recognition scores were significantly affected by and correlated with the extents of HF SNHL. The time-compressed speech recognition scores also correlated with the 1 kHz gap detection thresholds except when the compression ratio of speech was 0.8 under quiet condition. Above all, the extents of HF SNHL were significantly correlated with the 1 kHz gap thresholds.

It is hypothesized that in sine-wave replicas of natural speech, lexical tone recognition would be severely impaired due to the loss of F0 information, but the linguistic information at the sentence level could be retrieved even with limited tone information. Forty-one native Mandarin-Chinese-speaking listeners participated in the experiments. Results showed that sine-wave tone-recognition performance was on average only 32.7% correct. However, sine-wave sentence-recognition performance was very accurate, approximately 92% correct on average. Therefore the functional load of lexical tones on sentence recognition is limited, and the high-level recognition of sine-wave sentences is likely attributed to the perceptual organization that is influenced by top-down processes.

Objectives (1) To determine whether high-frequency sensorineural hearing loss (HF SNHL) is accompanied by deterioration in temporal resolution in the low-frequency region where hearing sensitivity is within normal range. (2) To evaluate whether such temporal processing deficits contribute to speech perception difficulty in noise. Design A between-group design was employed, using subjects either with or without high-frequency hearing loss and matched by age. Temporal resolution was evaluated in amplitude modulation (AM) detection and gap detection tasks. To restrict evaluation to the low-frequency regions where the auditory sensitivity was virtually normal, low-pass noise carriers (for AM detection) and gap markers (for gap detection) were used. The impact of temporal processing deficits on speech perception was evaluated using hearing in noise tests (HINT) with varied time compression rates of the speech materials. Results Adults with high-frequency hearing loss showed poorer performance than the age-matched normal-hearing subjects on both the AM and gap detection tasks, even though the stimuli were restricted to regions of observed normal sensitivity. With increasing time compression, listeners with HF SNHL required a larger signal to noise ratio to maintain accuracy in speech perception in adaptive HINT and exhibited a bigger decrease in score for HINTs at a fixed signal to noise ratio. Multiple regression/correlation analyses show significant correlation across the scores of AM/gap detection tasks and HINTs. Conclusions Temporal resolution in the low-frequency region with near-normal sensitivity seems to be deteriorated in subjects with HF SNHL. They were more sensitive to increases in speech rate, suggesting that poorer temporal processing may be related to speech perception deficits in noise.

Conclusion. High-frequency overstimulation can cause the loss of duration selectivity in low-frequency inferior colliculus neurons in guinea pigs. Objective. To investigate the effect of high-frequency overstimulation on duration tuning in low-frequency inferior colliculus neurons in guinea pigs. Materials and methods. Duration tuning pattern was recorded by measuring the spikes of single neurons in response to the best frequency (BF) of different durations. The effect of high-frequency overstimulation was verified by comparing the responses before and after the tone exposure. Results. In total, 40 duration-tuned neurons were successfully recorded before and after the tone exposure. After the high-frequency tone trauma, a total of 29 neurons (72.5%) became non-duration-tuned.

Neural tuning to sound durations is a useful filter for the identification of a variety of sounds. Previous studies have shown that the interaction between excitatory and inhibitory inputs plays a role in duration selectivity in echolocating bats. However, this has not been investigated in non-echolocating mammals. In the inferior colliculus (IC) of these mammals, it is recognized that the excitatory responses to sounds are mediated through AMPA and NMDA receptors while the inhibitory input is mediated through γ-aminobutyric acid (GABA) and glycine receptors. The present study explores the potential interplay between inhibitory and excitatory inputs and its role in the duration selectivity of IC neurons in guinea pigs. It was found that the application of bicuculline (BIC, a GABA A blocker) and/or strychnine (STRY, a glycine blocker) eliminated or reduced duration tuning in most units that were duration tuned (32 out of 39 for BIC, 50 out of 64 for STRY, respectively). The inhibitory input (either by GABA or by glycine) appeared to have a stronger regulating effect on the early excitation mediated by AMPA than on later excitation by NMDA. This is more distinguishable in neurons that show duration selectivity. In conclusion, the inhibitory effect on the early responses appears to be the main contributor for the duration selectivity of the IC in guinea pigs; potential mechanisms for this duration selectivity are also discussed.

Conclusion. GABA-mediated inhibition is responsible for the duration tuning in the inferior colliculus (IC) of guinea pigs, a non-echo-locating mammal. Duration tuning in this species is better demonstrated in an appropriate short time window. Objectives. To investigate the role of GABA-mediated inhibition in duration tuning of neurons in the IC of guinea pigs. Materials and methods. Duration tuning pattern was recorded by measuring the spikes of single neurons in response to broadband noise of different durations. The effect of GABA-mediated inhibition was verified by comparing the responses with and without the use of the GABA-A receptor blocker bicuculline (BIC), which was applied using micro-iontophoresis. Results. In addition to overall increase in responsiveness, the application of BIC was found to significantly reduce or eliminate the duration selectivity in 44 of the 67 neurons that showed clear duration tuning from a sample of total 340 neurons.

OBJECTIVES To study the relative contribution of acoustic temporal fine structure (TFS) cues in low-, mid-, and high-frequency regions to Mandarin sentence recognition. DESIGN Twenty-one subjects with normal hearing were involved in a study of Mandarin sentence recognition using acoustic TFS. The acoustic TFS information was extracted from 10 3-equivalent rectangular bandwidth-wide bands within the range 80 to 8858 Hz using the Hilbert transform and was assigned to low-, mid-, and high-frequency regions. Percent-correct recognition scores were obtained with acoustic TFS information presented using one, two, or three frequency regions. The relative weights of the three frequency regions were calculated using the least-squares approach. RESULTS Results indicated that the mean percent-correct scores for sentence recognition using acoustic TFS were nearly perfect for stimuli with all three frequency regions together. Recognition was approximately 50 to 60% correct with only the low- or mid-frequency region but decreased to approximately 5% correct with only the high-frequency region of acoustic TFS. The mean weights of the low-, mid-, and high-frequency regions were 0.39, 0.48, and 0.13, respectively, and the difference between each pair of frequency regions was statistically significant. CONCLUSION The acoustic TFS cues in low- and mid-frequency regions convey greater information for Mandarin sentence recognition, whereas those in the high-frequency region have little effect.

Objectives Tonsillotomy has gained popular acceptance as an alternative to the traditional tonsillectomy in the management of sleep-disordered breathing in children. Many studies have evaluated the outcomes of the two techniques, but uncertainty remains with regard to the efficacy and complications of tonsillotomy versus a traditional tonsillectomy. This study was designed to investigate the efficacy and complications of tonsillotomy versus tonsillectomy, in terms of the short- and long-term results. Methods We collected data from electronic databases including MEDLINE, EMBASE, and the Cochrane Library. The following inclusion criteria were applied: English language, children, and prospective studies that directly compared tonsillotomy and tonsillectomy in the management of sleep disordered breathing. Subgroup analysis was then performed. Results In total, 10 eligible studies with 1029 participants were included. Tonsillotomy was shown to be advantageous over tonsillectomy in short-term measures, such as a lower hemorrhage rate, shorter operation time, and faster pain relief. In long-term follow-up, there was no significant difference in resolution of upper-airway obstructive symptoms, the quality of life, or postoperative immune function between the tonsillotomy and tonsillectomy groups. The risk ratio of SDB recurrence was 3.33 (95% confidence interval = 1.62 6.82, P = 0.001), favoring tonsillectomy at an average follow-up of 31 months. Conclusions Tonsillotomy may be advantageous over tonsillectomy in the short term measures and there are no significant difference of resolving obstructive symptoms, quality of life and postoperative immune function. For the long run, the dominance of tonsillotomy may be less than tonsillectomy with regard to the rate of sleep-disordered breathing recurrence.

We explored possible relationships between sudden sensorineural hearing loss (SSNHL) in patients differing in terms of audiographic data and the levels of vascular markers in routine blood data.We included 37 patients with low-frequency SSNHL (LF-SSNHL), 28 with high-frequency SSNHL (HF-SSNH

To examine the value of self-treatment for Posterior canal benign paroxysmal positional vertigo (PC-BPPV). The treatment effect was compared between patients treated with modified Epley in outpatient clinic combined with self treatment at home and patients treated by modified Epley alone.A randomized controlled trial were carried out in the Department of Otolaryngology Head and Neck Surgery, the Affiliated Sixth People's Hospital of Shanghai Jiao Tong University from December 2012 to May 2013. 147 out of 150 patients with unilateral idiopathic BPPV-PSC were enrolled in follow-up. Among which, 73 patients were allocated in modified Epley-alone group and 74 were allocated in slef-treatment group.The success rate was 53.4% in modified Epley-alone group vs 83.8% in self-treatment group (P0.01) after 1 week treatment. In the modified Epley-alone group,the success rate of hand repositioning group and chair-assisted repositioning group was 45.9% vs 61.1% (P0.05), the risk rate was 0.752, 95% CI (0.486 - 1.163). In the self-treatment group, the success rate of hand repositioning group and chair-assisted repositioning group was 87.5% vs 81.0% (P0.05), the risk rate was 1.081, 95% CI (0.888-1.316). Incidence rate of serious complications was 0% in the modified Epley-alone group and 1.3% in the self-treatment group (P0.05).Complementary self-treatment with modified Epley maneuver treated PC-BPPV sooner and more effectively, Compared with modified Epley maneuver alone. And its incidence rate of serious complications didn't increase. Chair-assisted repositioning showed better result than hand repositioning alone, and self-treatment at home can reduce the effect of the gap. We found that complementary self-treatment with modified Epley maneuver had more benefits for patients with PC-BPPV.

Conclusion: Vertigo treatment and rehabilitation chair (TRV) may be suggested as the first choice for patients with posterior canal benign paroxysmal positional vertigo (p-BPPV). Objective: To investigate the short- and long-term treatment efficacy of the canalith repositioning procedure (CRP) versus TRV for patients with p-BPPV. Methods: A total of 165 patients with unilateral p-BPPV were assigned to either the CRP group or the TRV group. Patients were assessed at 1 week, 4 weeks, 3 months, and 6 months after their first treatment. The numbers of treatment sessions required for successful repositioning in both groups at 4 weeks, 3 months, and 6 months were recorded. Results: Treatment efficacy of patients in the TRV group was significantly better than that of patients in the CRP group 1 week after the first treatment. The number of treatment sessions needed for successful repositioning was significantly lower in the TRV group than in the CRP group at 4 weeks and 3 months after the first treatment.

To investigate the effect of the anti-laminin receptor 1 (anti-LAMR1) monoclonal antibody (mAb) on rat pulmonary fibrosis induced by bleomycin.Seventy-two male Wistar rats were randomly divided into 3 groups: LAMR1 mAb group (group L), control group (group C) and model group (group M). All rats were injected with bleomycin via tracheal instillation (5 mg/kg body mass) to induce pulmonary fibrosis. Then, the rats were treated with anti-LAMR1 mAb (group L), dexamethasone (group C), normal saline (group M), three times each week via intraperitoneal injection. Eight rats in each group were sacrificed at the 7, 14, 28 days. Histological changes of the lungs were evaluated by HE staining. The expression of surfactant protein A (SP-A) in the lung tissue was measured by immunohistochemistry. The expression of hydroxyproline (Hyp) in serum was measured by ELISA. The expressions of MMP-9 and TGF-β1 mRNA were evaluated by PCR.Compared with the other two groups, group M presented more apparent alveolitis and the higher expression of hydroxyproline in serum, the lower expression of SP-A, and the higher expressions of MMP-9 and TGF-β1 mRNA in the lung tissue.LAMR1 mAb can evidently alleviate pulmonary fibrosis induced by bleomycin in rats.

Objective Repetitive Transcranial Magnetic Stimulation (rTMS) is a novel therapeutic tool to induce a suppression of tinnitus. However, the optimal target sites are unknown. We aimed to determine whether low-frequency rTMS induced lasting suppression of tinnitus by decreasing neural activity in the cortex, navigated by high-density electroencephalogram (EEG) source analysis, and the utility of EEG for targeting treatment. Methods In this controlled three-armed trial, seven normal hearing patients with tonal tinnitus received a 10-day course of 1-Hz rTMS to the cortex, navigated by high-density EEG source analysis, to the left temporoparietal cortex region, and to the left temporoparietal with sham stimulation. The Tinnitus handicap inventory (THI) and a visual analog scale (VAS) were used to assess tinnitus severity and loudness. Measurements were taken before, and immediately, 2 weeks, and 4 weeks after the end of the interventions. Results Low-frequency rTMS decreased tinnitus significantly after active, but not sham, treatment. Responders in the EEG source analysis-based rTMS group, 71.4% (5/7) patients, experienced a significant reduction in tinnitus loudness, as evidenced by VAS scores. The target site of neuronal generators most consistently associated with a positive response was the frontal lobe in the right hemisphere, sourced using high-density EEG equipment, in the tinnitus patients. After left temporoparietal rTMS stimulation, 42.8% (3/7) patients experienced a decrease in tinnitus loudness. Conclusions Active EEG source analysis based rTMS resulted in significant suppression in tinnitus loudness, showing the superiority of neuronavigation-guided coil positioning in dealing with tinnitus. Non-auditory areas should be considered in the pathophysiology of tinnitus. This knowledge in turn can contribute to investigate the pathophysiology of tinnitus.

Pneumocystis pneumonia (PCP) occurs predominately in patients with impaired immunity. Because standard PCP chemoprophylaxis and chemotherapies have limitations, immunotherapy, particularly vaccination, offers an attractive alternative approach for PCP prevention and treatment. The goal of this study was to evaluate the potential of DNA vaccines targeting two closely related antigens, p55-v0 and p55-v3, in an immunosuppressed rat PCP model. We found that immunization with p55-v0 and p55-v3 DNA vaccines afforded a similar level of protection to rats against PCP, as evidenced by significant reductions in organism burdens, improved histological scores, and lower lung weight to body weight ratios. Additionally, vaccination elicited both cellular and humoral immunity in immunosuppressed rats. Our data suggest the potential of p55 DNA vaccines to protect against PCP in rats. Future work should focus on epitope mapping and identifying protective moieties in each gene.

Temporal modulation transfer function (TMTF) is one of the most common methods for evaluating temporal acuity in the auditory system. In this experiment, we recorded cortical responses to amplitude modulation of tone carriers from implanted electrodes in guinea pigs to generate TMTFs by calculating the response amplitude changes as a function of modulation frequencies (Mfs). High-frequency hearing loss above 8 kHz was established using tone overstimulation (12 kHz, 110 dB SPL for 30 hours). The impact of this acoustic trauma on temporal resolution in the low-frequency range (below and at 8 kHz) was evaluated with the repeated tests of TMTFs until eight weeks post trauma. Deterioration in temporal resolution was found to develop over time, especially at 2 kHz, which was indicated by the decrease in −3 dB cutoffs in TMTFs and by the overall decrease in the AM response amplitude. Potential mechanisms that may underlie this off-channel affect are discussed.SumarioLa funcion de transferencia de la modu...

Test of amplitude modulation detection threshold against modulation frequency (Mf) is one of the major measures in behavior studies for exploring temporal acuity of the auditory system. In this experiment, we recorded cortical responses from implanted electrodes in guinea pigs to generate temporal modulation transfer functions (TMTFs) by calculating the response amplitude changes across a range of Mfs in order to evaluate the temporal resolution in different frequency regions. A −3 dB cutoff frequency was measured from each TMTFs and was used as a single-value index for temporal resolution. We found that the temporal resolution, as represented by this index, did not change significantly with the carrier frequency. This result suggested that the temporal resolution of the auditory system is not simply determined by the bandwidth of peripheral auditory channels. We further evaluated the effects of the general anesthesia by pentobarbital on temporal acuity and found that, in addition to the suppressions of response amplitude, this anesthesia significantly decreases the −3 dB cutoff frequencies of TMTF.

Gap detection has been used as an evaluation tool for temporal processing in subjects with sensorineural hearing loss (SNHL). However, the results from other reports are varied making it difficult to clearly define the impact of SNHL on the temporal processing ability of the auditory system. Specifically, we do not know if and how a high-frequency hearing loss impacts, presumably through off-channel interaction, the temporal processing in low-frequency channels where hearing sensitivity is virtually normal. In this experiment, gap-evoked responses in a low-frequency band (0.5-8 kHz) were recorded in the inferior colliculus (IC) and auditory cortex (AC) of guinea pigs through implanted electrodes, before and after a slopping high-frequency hearing loss, which was induced by over-stimulation using a 12-kHz-tone. The results showed that the gap thresholds in the low-frequency region increased gradually and became significantly higher 8 weeks after the induced high-frequency hearing loss. In addition, the response latency was slightly increased in the IC but this was not true for the AC. These results strongly indicate that a high-frequency hearing loss exerted an off-channel impact on temporal processing in the low-frequency region of the auditory system.

Conclusion. General anesthesia induced by sodium pentobarbital reduces temporal resolution as represented by an increase in the threshold of gap-evoked auditory responses in guinea pigs. Objectives. To explore the potential impact of general anesthesia by sodium pentobarbital (PB), a common anesthetic used in animal research, on gap-evoked responses. Materials and methods. The evoked potentials in response to gaps formed by bursts of broadband noise were recorded from electrodes implanted in the inferior colliculus (IC) and the auditory cortex (AC) of guinea pigs. The gap responses were compared in three conditions: unanesthetized and anesthetized with two doses of sodium pentobarbital (40 mg/kg and 20 mg/kg). Results. PB increased the gap response thresholds, especially when applied at the higher dose. The threshold shift induced by PB was greater in the AC than in the IC. In addition, the higher dose of PB significantly increased the gap response latency in both IC and AC, and decreased response amplitu...