Research progress of the regulation of cochlear sensitivity to noise by circadian rhythm / 生理学报

High level noise can damage cochlear hair cells, auditory nerve and synaptic connections between cochlear hair cells and auditory nerve, resulting in noise-induced hearing loss (NIHL). Recent studies have shown that animal cochleae have circadian rhythm, which makes them different in sensitivity to noise throughout the day. Cochlear circadian rhythm has a certain relationship with brain-derived neurotrophic factor and glucocorticoids, which affects the degree of hearing loss after exposure to noise. In this review, we summarize the research progress of the regulation of cochlear sensitivity to noise by circadian rhythm and prospect the future research direction.

Longitudinal Changes in Liver Aminotransferases Predict Metabolic Syndrome in Chinese Patients with Nonviral Hepatitis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>This study explored the correlation of longitudinal changes in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels with the incidence of metabolic syndrome (Mets) based on a dynamic health examination cohort.</p><p><b>METHODS</b>A Mets-free dynamic cohort involving 4541 participants who underwent at least three health examinations from 2006 to 2011 was included in the study. Mets was defined according to the Chinese Medical Association Diabetes Branch definition that included hypertension, obesity, hyperlipidemia, and hyperglycemia. Generalized estimating equation (GEE) model was used to analyze multivariate relative risk (RR) of repeated observations of ALT and AST in quartiles for Mets or its components according to gender.</p><p><b>RESULTS</b>In all, 826 Mets cases were reported. Adjustment of relevant parameters indicated that time-varying changes in ALT and AST levels were positively associated with the incidence of Mets in a dose-response manner. Positive association between high ALT levels and fatty liver was much stronger than that between high AST levels and fatty liver, particularly in male participants. These associations were consistently observed in the following subgroups: participants with ALT and AST levels of <40 U/L, participants with of <25 kg/m2, and participants with non-fatty liver. Furthermore, participants with 2 Mets components at baseline showed lower multivariate adjusted RRs of ALT and AST for Mets than participants with 0-1 Mets component.</p><p><b>CONCLUSION</b>These results suggested that elevated serum ALT and AST levels were early biomarkers of Mets or its components.</p>

Research progress in neurophysiological mechanism underlying distinguishing plants through classification of echoes in frequency modulation bats / 生理学报

By using echolocation system echolocating bats have the ability to complete the tasks of detection, localization and classification of the targets. Among the three fundamental tasks, the study of how bats use echolocation to classify targets was investigated later, and most of previous studies were focused on the analysis of simple targets. However, the echoes that bats received are mostly returning from complex objects or structures, which are so complex that they must be described by stochastic statistical approach. In recent years, the study on classification of complex echoes returning from different plants in frequency modulation (FM) bats has made significant progress. In this review article, we will briefly introduce and comment on some progress of studies based on the behavioral evidence, acoustic cues, relevant classification models, and neural bases underlying different classification cues to distinguish plants through classification of echoes in FM bats.

In vitro whole-cell patch clamp recordings of neurons in subnuclei of mouse inferior colliculus / 生理学报

The inferior colliculus (IC) is a pivot along the central auditory pathway. Using infrared visual whole-cell patch clamp recording technique, we investigated the electrophysiological properties of IC subnuclei neurons. Recordings were made from 88 neurons, including 21 neurons from the dorsal cortex of the IC (ICd), 43 neurons from the central nucleus of the IC (ICc) and 24 neurons from the external cortex of the IC (ICx). Based on the responses to positive current injection, three firing patterns, i.e., onset (6.8%, n = 6), adapting (39.8%, n = 35) and sustained (53.4%, n = 47) patterns, were identified. The hyperpolarization-activated inward current (Ih) could be recorded in half of the neurons (49/88). The sustained pattern occurred in more than half of ICd and ICc neurons (61.9% and 67.4%), while the adapting pattern occurred in majority of ICx neurons (75%). Action potential (AP) threshold and time constant also showed significant differences across neurons from the ICd, the ICc and the ICx. Our results indicate that IC neurons are different in electrophysiological properties across the subnuclei. The variance of the responses may be related to the distinct types of neurons as well as the received projections, which is implicated in the distinct roles of IC neurons in central auditory processing.

Relation between frequency modulation direction selectivity and forward masking of inferior collicular neurons: a study on in vivo intracellular recording in mice / 生理学报

It has been reported that the frequency modulation (FM) or FM direction sensitivity and forward masking of central auditory neurons are related with the neural inhibition, but there are some arguments, because no direct evidence of inhibitory synaptic input was obtained in previous studies using extracellular recording. In the present study, we studied the relation between FM direction sensitivity and forward masking of the inferior collicular (IC) neurons using in vivo intracellular recordings in 20 Mus musculus Km mice. Thirty seven with complete data among 93 neurons were analyzed and discussed. There was an inhibitory area which consisted of inhibitory postsynaptic potentials (IPSP) at high frequency side of frequency tuning of up-sweep FM (FMU) sensitive neurons (n = 12) and at low frequency side of frequency tuning of down-sweep FM (FMD) selective neurons (n = 8), while there was no any inhibitory area at both sides of frequency tuning of non-FM sweep direction (FMN) sensitive neurons (n = 17). Therefore, these results show that the inhibitory area at low or high frequency side of frequency tuning is one of the mechanisms for forming FM sweep direction sensitivity of IC neurons. By comparison of forward masking produced by FMU and FMD sound stimuli in FMU, FMD and FMN neurons, the selective FM sounds could produce stronger forward masking than the non-selective in FMU and FMD neurons, while there was no forward masking difference between FMU and FMD stimuli in the FMN neurons. We suggest that the post-action potential IPSP is a potential mechanism for producing stronger forward masking in FMU and FMD neurons.

Effects of modulation range and presentation rate of FM stimulus on auditory response properties of mouse inferior collicular neurons / 生理学报

In natural acoustical environments, most biologically related sounds containing frequency-modulated (FM) components repeat over periods of time. They are often in rapid sequence rather than in temporal isolation. Few studies examined the neuronal response patterns evoked by FM stimuli at different presentation rates (PR). In the present investigation, by using normal electrophysiological technique, we specifically studied the temporal features of response of the inferior collicular (IC) neurons to FM sweeps with different modulation ranges (MR) in conditions of distinct PR in mouse. The results showed that most of the recorded neurons responded best to narrower MRs (narrow-pass, up-sweep: 60.00%, 54/90; down-sweep: 63.33%, 57/90), while a small fraction of neurons displayed other patterns such as band-pass (up-sweep, 16.67%, 15/90; down-sweep, 18.89%, 17/90), all-pass (up-sweep, 18.89%, 17/90; down-sweep, 13.33%, 12/90) and wide-pass (up-sweep, 4.44%, 4/90; down-sweep, 4.44%, 4/90). Both the discharge rate and duration of recorded neurons decreased but the latency lengthened with increase in PR, when different PRs from 0.5/s to 10/s of FM sound were used. The percentage of total directional selective neurons, up-directional selective neurons, and down-directional selective neurons changed with the variation of PR or MR. These results indicate that temporal features of mouse midbrain neurons responding to FM sweeps are co-shaped by the MR and PR. Possible mechanisms underlying may be related to spectral and temporal integration of the FM sound by the IC neurons.

Effects of cold stress on blood cell parameters of partial sleep deprivation mice / 中国应用生理学杂志

<p><b>AIM</b>To investigate the effect of cold, partial sleep deprivation, partial sleep deprivation plus cold on blood routine parameters and erythrocyte sedimentation rate of mice.</p><p><b>METHODS</b>Twenty-four Mus musculus mice were divided into four groups (n=6) randomly: (1) control, (2) cold group: mice were treated with (10 +/- 2) degrees C cold stimulation for four hours per day, (3) partial sleep deprivation group: mice were deprived sleep from 18:00 to 9:00 next day, (4) partial sleep deprivation plus cold group: mice were treated with cold stimulation based on partial sleep deprivation. After four days treatment, the mice were sacrificed and the blood was collected to detect the blood routine parameters and erythrocyte sedimentation rate.</p><p><b>RESULTS</b>Compared with the control, cold stimulation would increase the contents and proportion of lymphocyte significantly. Partial sleep deprivation would decrease the white blood cell contents, lymphocyte contents and lymphocyte proportion significantly. After treated with cold stimulation plus partial sleep deprivation, the white blood cell and lymphocyte contents decreased and the erythrocyte sedimentation rate increased evidently compared with other three groups.</p><p><b>CONCLUSION</b>Partial sleep deprivation could inhibit immune function of the mice. When the mice were treated with cold stimulation plus partial sleep deprivation, the immune function of the mice would be inhibited further more and at the same time the erythrocyte sedimentation rate increased significantly.</p>

Selectivity for the rate of frequency-modulated sweeps and its affecting factors in the inferior collicular neurons of mouse / 生理学报

Both animal communication sounds and human speech contain frequency-modulated (FM) sweeps. Although the selectivity for the rate of FM sweeps in neurons has been found in many kinds of animals at different levels of the central auditory structures, the underlying neural mechanism is still not clear. Using extracellular single unit recording techniques, we examined the selectivity for the rate of FM sweeps in the inferior colliculus (IC) neurons of the Kunming mouse (Mus musculus, Km) in the free-field stimulation conditions and determined its affecting factors. Totally, 102 neurons were recorded successfully, among which 42 neurons (41.2%) displayed a duration tuning pattern under pure tone (PT) stimulus. The percentages of short-pass, band-pass, and long-pass neurons were 22.6% (23/10), 8.8% (9/102), 9.8% (10/102), respectively. The other 60 neurons (58.8%) did not show any duration tuning features. Under FM stimulus, the majority of duration tuning neurons (78.6%, 33/42) showed the selectivity for the rate of FM sweeps. For these neurons, the type of rate selectivity was determined by the duration tuning features, but it was not related to the modulation range (MR) of FM. In a small fraction of duration tuning neurons (21.4%, 9/42), the rate selectivity was correlated with the MR, but uncorrelated with the duration tuning features. On the other hand, more than half of the non-duration tuning neurons (53.3%, 32/60) exhibited the rate selectivity under FM stimulus, and almost all of them (31/32) showed fast-rate selectivity. Nevertheless, there were 8 neurons (in 32) displaying the same best rate at different MR, indicating that they were real rate-selective neurons. Our results indicate that the selectivity for the rate of FM sweeps is co-determined by duration tuning features and sweep bandwidth. Only a few of inferior colliculus neurons belong to real rate-selectivity neurons in the mouse.

Different forward masking patterns of sustained noise burst and segmental noise burst in the inferior collicular neurons of the mouse / 生理学报

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.

Dynamic modulations on intensity sensitivity evoked by weak noise in the inferior collicular neurons / 生理学报

In order to explore the possible mechanisms by which ethologically relevant sounds can be extracted from complex auditory environments, this study examined the effects of weak noise on the rate-intensity functions (RIFs) of neurons responding to tone burst in the inferior colliculus (IC) of nine mice (Mus musculus Km). Under free field stimuli conditions, a total of 112 IC neurons were recorded. RIFs with and without simultaneous presentation of weak noise, of which the intensity was relative to 5 dB below minimum threshold of tone burst, were measured in 44 IC neurons. By means of evaluating the changes of dynamic range (DR), slope of RIFs, and percent inhibition at different tone burst intensities evoked by the weak noise, three types of variations in RIFs were observed, i. e., inhibition (39/44, 88.6%), facilitation (2/44, 4.6%), and no effectiveness (3/44, 6.8%). Statistical analysis indicated that only inhibitory effect of weak noise was significant (P< 0.001, n = 39). The inhibitory effect of weak noise was greater at lower stimulus intensity of tone burst but decreased significantly with increased stimulus intensity (P< 0.0001, n = 39). In addition, the DR and slope of RIFs became narrower and steeper with weak noise presentation, respectively (P< 0.01, n = 31). The results from the present study suggest that weak noise exerts a dynamic modulatory action on acoustical intensity sensitivity of IC neurons, which possibly leads to a better understanding of neural mechanisms underlying the extraction of sound signals from natural auditory scenes.