Broad nonlinearity in reticular lamina vibrations requires compliant organ of Corti structures.

In the mammalian cochlea, each longitudinal position of the basilar membrane (BM) has a nonlinear vibratory response in a limited frequency range around the location-dependent frequency of maximum response, known as the best frequency (BF). This nonlinear response arises from the electromechanical feedback from outer hair cells (OHCs). However, recent in vivo measurements have demonstrated that the mechanical response of other organ of Corti (OoC) structures, such as the reticular lamina (RL), and the electrical response of OHCs (measured in the local cochlear microphonic [LCM]) are nonlinear even at frequencies significantly below BF. In this work, a physiologically motivated model of the gerbil cochlea is used to demonstrate that the source of this discrepancy between the frequency range of the BM, RL, and LCM nonlinearities is greater compliance in the structures at the top of the OHCs. The predicted responses of the BM, RL, and LCM to pure tone and two-tone stimuli are shown to be in line with experimental evidence. Simulations then demonstrate that the sub-BF nonlinearity in the RL requires the structures at the top of the OHCs to be significantly more compliant than the BM. This same condition is also necessary for "optimal" gain near BF, i.e., high amplification that is in line with the experiment. This demonstrates that the conditions for OHCs to operate optimally at BF inevitably yield nonlinearity of the RL response over a broad frequency range.

Link between stimulus otoacoustic emissions fine structure peaks and standing wave resonances in a cochlear model.

In response to an external stimulus, the cochlea emits sounds, called stimulus frequency otoacoustic emissions (SFOAEs), at the stimulus frequency. In this article, a three-dimensional computational model of the gerbil cochlea is used to simulate SFOAEs and clarify their generation mechanisms and characteristics. This model includes electromechanical feedback from outer hair cells (OHCs) and cochlear roughness due to spatially random inhomogeneities in the OHC properties. As in the experiments, SFOAE simulations are characterized by a quasiperiodic fine structure and a fast varying phase. Increasing the sound pressure level broadens the peaks and decreases the phase-gradient delay of SFOAEs. A state-space formulation of the model provides a theoretical framework to analyze the link between the fine structure and global modes of the cochlea, which arise as a result of standing wave resonances. The SFOAE fine structure peaks correspond to weakly damped resonant modes because they are observed at the frequencies of nearly unstable modes of the model. Variations of the model parameters that affect the reflection mechanism show that the magnitude and sharpness of the tuning of these peaks are correlated with the modal damping ratio of the nearly unstable modes. The analysis of the model predictions demonstrates that SFOAEs originate from the peak of the traveling wave.

Nonproliferative diabetic retinopathy dataset(NDRD): A database for diabetic retinopathy screening research and deep learning evaluation.

OBJECTIVES: In this article, we provide a database of nonproliferative diabetes retinopathy, which focuses on early diabetes retinopathy with hard exudation, and further explore its clinical application in disease recognition. METHODS: We collect the photos of nonproliferative diabetes retinopathy taken by Optos Panoramic 200 laser scanning ophthalmoscope, filter out the pictures with poor quality, and label the hard exudative lesions in the images under the guidance of professional medical personnel. To validate the effectiveness of the datasets, five deep learning models are used to perform learning predictions on the datasets. Furthermore, we evaluate the performance of the model using evaluation metrics. RESULTS: Nonproliferative diabetes retinopathy is smaller than proliferative retinopathy and more difficult to identify. The existing segmentation models have poor lesion segmentation performance, while the intersection over union (IOU) value for deep lesion segmentation of models targeting small lesions can reach 66.12%, which is higher than ordinary lesion segmentation models, but there is still a lot of room for improvement. CONCLUSION: The segmentation of small hard exudative lesions is more challenging than that of large hard exudative lesions. More targeted datasets are needed for model training. Compared with the previous diabetes retina datasets, the NDRD dataset pays more attention to micro lesions.

Intracochlear distortion products are broadly generated by outer hair cells but their contributions to otoacoustic emissions are spatially restricted.

Detection of low-level sounds by the mammalian cochlea requires electromechanical feedback from outer hair cells (OHCs). This feedback arises due to the electromotile response of OHCs, which is driven by the modulation of their receptor potential caused by the stimulation of mechano-sensitive ion channels. Nonlinearity in these channels distorts impinging sounds, creating distortion-products that are detectable in the ear canal as distortion-product otoacoustic emissions (DPOAEs). Ongoing efforts aim to develop DPOAEs, which reflects the ear's health, into diagnostic tools for sensory hearing loss. These efforts are hampered by limited knowledge on the cochlear extent contributing to DPOAEs. Here, we report on intracochlear distortion products (IDPs) in OHC electrical responses and intracochlear fluid pressures. Experiments and simulations with a physiologically motivated cochlear model show that widely generated electrical IDPs lead to mechanical vibrations in a frequency-dependent manner. The local cochlear impedance restricts the region from which IDPs contribute to DPOAEs at low to moderate intensity, which suggests that DPOAEs may be used clinically to provide location-specific information about cochlear damage.

Investigation of the 2f1-f2 and 2f2-f1 distortion product otoacoustic emissions using a computational model of the gerbil ear.

In this work, a three-dimensional computational model of the gerbil ear is used to investigate the generation of the 2f1-f2 and 2f2-f1 distortion product otoacoustic emissions (DPOAEs). In order to predict both the distortion and reflection sources, cochlear roughness is modeled by introducing random inhomogeneities in the outer hair cell properties. The model was used to simulate the generation of DPOAEs in response to a two-tone stimulus for various primary stimulus levels and frequency ratios. As in published experiments, the 2f1-f2 DPOAEs are mostly dominated by the distortion component while the 2f2-f1 DPOAEs are dominated by the reflection component; furthermore, the influence of the levels and frequency ratio of the primaries are consistent with measurements. Analysis of the intracochlear response shows that the distortion component has the highest magnitude at all longitudinal locations for the 2f1-f2 distortion product (DP) while the distortion component only dominates close to the DP best place in the case of the 2f2-f1 DP. Decomposition of the intracochlear DPs into forward and reverse waves demonstrates that the 2f1-f2 DP generates reverse waves for both the distortion and reflection components; however, a reverse wave is only generated for the reflection component in the case of the 2f2-f1 DP. As in experiments in the gerbil, the group delay of the reflection component of the DPOAE is between 1× and 2× the forward group delay, which is consistent with the propagation of DP towards the stapes as slow reverse waves.

[Effect of electroacupuncture on CD 34+ endothelial progenitor cell counts in bone marrow and peripheral blood in focal cerebral ischemia/reperfusion rats].

OBJECTIVE: To observe the effect of electroacupuncture (EA) on CD 34+ endothelial progenitor cells (EPCs) in bone marrow and peripheral blood and the expression of p-AKT protein in bone marrow in focal cerebral ischemia/reperfusion (CI/R) rats, so as to investigate its mechanism underlying improvement of cerebral ischemia. METHODS: A total of 108 male SD rats were randomly divided into sham operation (sham) group, model (CI/R) group, and EA group which were further divided into 12, 24, 48 h subgroups (n = 12/group, 6 rats for biochemical analysis and the other 6 rats for Western blot analysis). Cl/R model was established by occlusion of the right middle cerebral artery for 2 hours followed by reperfusion. EA (2 Hz/20 Hz) was applied to "Baihui"(GV 20), left "Hegu" (LI 4) and left "Taichong" (LR 3) acupoints for 30 min, once daily. The neurological deficit scores were evaluated using Longa 5-grade standards. Flow cytometer was used to detect the percentages of CD 34+ EPCs in bone marrow and peripheral blood. The expression of p-AKT protein of bone marrow was detected by Western blot. RESULTS: In comparison with the CIl/R model group, the neurological deficit score were gradually and significantly decreased 48 h after CI/R in the EA group (P<0. 05), suggesting an improvement of the neurological function after EA. Compared with the sham group, the percentages of CD 34+ EPCs in bone marrow and peripheral blood and the expression level of bone-marrow p-AKT protein were significantly up-regulated in the model group at the three time-points after CI/R (P<0. 01, P<0. 05). Following EA intervention, the percentages of CD 34+ EPCs at the three time-points in the peripheral blood, and at time-points of 12 h and 24 h in the bone marrow, and the expression levels of p-AKT protein at the three time-points were significantly further up-regulated in the EA group in comparison with the model group (P<0.05, P<0.01). CONCLUSION: EA can effectively up-regulate the percentages of CD 34+ EPCs in the bone marrow and peripheral blood, and increase p-AKT protein expression in the bone marrow in CI/R rats, which may contribute to its effect in improving neurological function.