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- Trimodal Speech Perception: How Residual Acoustic Hearing Supplements Cochlear-Implant Consonant Recognition in the Presence of Visual Cues. [JOURNAL ARTICLE]
- Ear Hear 2014 Dec 15.
As cochlear implant (CI) acceptance increases and candidacy criteria are expanded, these devices are increasingly recommended for individuals with less than profound hearing loss. As a result, many individuals who receive a CI also retain acoustic hearing, often in the low frequencies, in the nonimplanted ear (i.e., bimodal hearing) and in some cases in the implanted ear (i.e., hybrid hearing) which can enhance the performance achieved by the CI alone. However, guidelines for clinical decisions pertaining to cochlear implantation are largely based on expectations for postsurgical speech-reception performance with the CI alone in auditory-only conditions. A more comprehensive prediction of postimplant performance would include the expected effects of residual acoustic hearing and visual cues on speech understanding. An evaluation of auditory-visual performance might be particularly important because of the complementary interaction between the speech information relayed by visual cues and that contained in the low-frequency auditory signal. The goal of this study was to characterize the benefit provided by residual acoustic hearing to consonant identification under auditory-alone and auditory-visual conditions for CI users. Additional information regarding the expected role of residual hearing in overall communication performance by a CI listener could potentially lead to more informed decisions regarding cochlear implantation, particularly with respect to recommendations for or against bilateral implantation for an individual who is functioning bimodally.Eleven adults 23 to 75 years old with a unilateral CI and air-conduction thresholds in the nonimplanted ear equal to or better than 80 dB HL for at least one octave frequency between 250 and 1000 Hz participated in this study. Consonant identification was measured for conditions involving combinations of electric hearing (via the CI), acoustic hearing (via the nonimplanted ear), and speechreading (visual cues).The results suggest that the benefit to CI consonant-identification performance provided by the residual acoustic hearing is even greater when visual cues are also present. An analysis of consonant confusions suggests that this is because the voicing cues provided by the residual acoustic hearing are highly complementary with the mainly place-of-articulation cues provided by the visual stimulus.These findings highlight the need for a comprehensive prediction of trimodal (acoustic, electric, and visual) postimplant speech-reception performance to inform implantation decisions. The increased influence of residual acoustic hearing under auditory-visual conditions should be taken into account when considering surgical procedures or devices that are intended to preserve acoustic hearing in the implanted ear. This is particularly relevant when evaluating the candidacy of a current bimodal CI user for a second CI (i.e., bilateral implantation). Although recent developments in CI technology and surgical techniques have increased the likelihood of preserving residual acoustic hearing, preservation cannot be guaranteed in each individual case. Therefore, the potential gain to be derived from bilateral implantation needs to be weighed against the possible loss of the benefit provided by residual acoustic hearing.
- Selecting the optimal anti-aliasing filter for multichannel biosignal acquisition intended for inter-signal phase shift analysis. [JOURNAL ARTICLE]
- Physiol Meas 2014 Dec 16; 36(1):N23-N34.
The availability of microcomputer-based portable devices facilitates the high-volume multichannel biosignal acquisition and the analysis of their instantaneous oscillations and inter-signal temporal correlations. These new, non-invasively obtained parameters can have considerable prognostic or diagnostic roles. The present study investigates the inherent signal delay of the obligatory anti-aliasing filters. One cycle of each of the 8 electrocardiogram (ECG) and 4 photoplethysmogram signals from healthy volunteers or artificially synthesised series were passed through 100-80-60-40-20 Hz 2-4-6-8th order Bessel and Butterworth filters digitally synthesized by bilinear transformation, that resulted in a negligible error in signal delay compared to the mathematical model of the impulse- and step responses of the filters. The investigated filters have as diverse a signal delay as 2-46 ms depending on the filter parameters and the signal slew rate, which is difficult to predict in biological systems and thus difficult to compensate for. Its magnitude can be comparable to the examined phase shifts, deteriorating the accuracy of the measurement. As a conclusion, identical or very similar anti-aliasing filters with lower orders and higher corner frequencies, oversampling, and digital low pass filtering are recommended for biosignal acquisition intended for inter-signal phase shift analysis.
- Nicotine facilitates reinnervation of phenol-injured perivascular adrenergic nerves in the rat mesenteric resistance artery. [JOURNAL ARTICLE]
- Eur J Pharmacol 2014 Dec 13.
Nicotine has been shown to have neuroprotective and neurotrophic actions in the central nervous system. To elucidate the peripheral neurotrophic effects of nicotine, we determined whether nicotine affected the reinnervation of mesenteric perivascular nerves following a topical phenol treatment. A topical phenol treatment was applied to the superior mesenteric artery proximal to the abdominal aorta in Wistar rats. We examined the immunohistochemistry of the distal small arteries 7 days after the treatment. The topical phenol treatment markedly reduced the density of tyrosine hydroxylase (TH)-LI and calcitonin gene-related peptide (CGRP)-LI fibers in these arteries. The administration of nicotine at a dose of 3mg/kg/day (1.5mg/kg/injection, twice a day), but not once a day or its continuous infusion using a mini-pump significantly increased the density of TH-LI nerves without affecting CGRP-LI nerves. A pretreatment with nicotinic acetylcholine receptor antagonists hexamethonium, mecamylamine, and methyllycaconitine, but not dextrometorphan, canceled the TH-LI nerve reinnervation induced by nicotine. Nicotine significantly increased NGF levels in the superior cervical ganglia (SCG) and mesenteric arteries, but not in the dorsal root ganglia, and also up-regulated the expression of NGF receptors (TrkA) in the SCG, which were canceled by hexamethonium. These results suggested that nicotine exhibited neurotrophic effects that facilitated the reinnervation of adrenergic TH-LI nerves by activating α7 nicotinic acetylcholine receptor and NGF in the SCG.
- Development and Validation of a Virtual Human Vignette to Compare Nurses' Assessment and Intervention Choices for Pain in Critically Ill Children. [JOURNAL ARTICLE]
- Simul Healthc 2014 Dec 15.
As virtual experiences are increasingly used in health care training and research, it is important that adequate processes are applied for developing valid scenarios. We describe the development and validation of virtual human (VH) vignettes, computer-generated scenarios with animated patients and clinical information, for a mixed-methods study regarding nurses' assessment and intervention choices for critically ill children's pain.We followed the case development and review process for high-fidelity simulation case scenarios, including the use of validated written vignettes and content experts. Forty nurses described their pain assessment and intervention choices for the newly derived VH vignettes and completed a pain questionnaire. Nurses' reports of VH vignette consistency with their professional experience and recognition of VH facial expressions were evaluated to establish face validity. Their pain ratings for the VH and written (questionnaire) vignettes were evaluated for convergent validity. Qualitative content analysis, descriptive statistics, correlations, and paired t tests were used.Most nurses (68.4%) supported vignette consistency with their professional experience. Facial expression recognition was 98.4%. Smiling children's pain was rated significantly lower than grimacing children in both VH and written vignettes. Pain was rated significantly lower for grimacing children in the VH vignettes than the written vignettes. Virtual human vignette pain ratings were strongly correlated with their written counterparts.This process was effective for developing VH vignettes that demonstrated good face validity with participants and convergent validity with written vignettes. Virtual human vignettes may be useful in studying the influence of facial actions on nurses' choices for children's pain assessment and treatment.
- Proteomic changes during tuber dormancy release process revealed by iTRAQ quantitative proteomics in potato. [JOURNAL ARTICLE]
- Plant Physiol Biochem 2014 Dec 4.:181-190.
Given that limited information is available with regard to tuber dormancy release related proteome, we conducted proteome analysis of tuber dormancy release process at dormant tuber (DT), dormancy release tuber (DRT) and sprouting tuber (ST) using the iTRAQ technology. A total of 1,752 proteins were identified. Among them, a subset of 316 proteins was screened as significant up- (137) and down regulated (179) between DT vs DRT. A subset of 120 proteins experienced significant up- (40) or down-regulation (80) between DRT vs ST. The differentially expressed proteins were grouped into 11 functional categories. Proteins enriched in functional categories of major carbohydrate (CHO) metabolism, glycolysis, fermentation, amino acid metabolism, protein and transport were highly up-regulated, while functional categories of photosynthesis and RNA were down-regulated between DT vs DRT. Proteins enriched in functional groups of protein, cell wall, lipid metabolism, miscellaneous, and signaling were strongly up-regulated, while functional categories of photosynthesis, hormone metabolism and protein were down-regulated between DRT vs ST. Consistent with previous documented differentially expressed genes, most of differentially expressed proteins were also identified between DT and DRT, indicating the metabolism shift from growth suspension to growth activation as tubers dormancy breaking. The changes in protein profiles showed lower concordance with corresponding alterations in transcript levels, indicating possible transcriptional and posttranscriptional regulation. Furthermore, the possible mechanism of tuber dormancy release was discussed in relation to what was known in transcripts change and other plant models from carbohydrate metabolism, protein metabolism, stress response, redox regulation, transcription regulation, DNA metabolism, amino acid metabolism, development, signaling as well as hormone metabolism.
- The feasibility of low-dose CT protocols for coronary artery calcium scoring and PET attenuation correction in cardiac PET/CT. [JOURNAL ARTICLE]
- Nucl Med Commun 2014 Dec 15.
The purpose of this study was to investigate the feasibility of using low-dose computed tomography (CT) in coronary artery calcium scoring and PET attenuation correction for patients in different weight categories undergoing cardiac PET/CT examinations.Calcium scoring computed tomography (CSCT) scans and PET scans of anthropomorphic cardiac phantoms simulating normal-weight, mildly obese, and severely obese patients were acquired with a hybrid PET/CT scanner. CSCT images were acquired at 120 kVp, with tube current ranging from 10 to 550 mA. PET scans were performed in three-dimensional mode, with acquisition time of 3 min/bed position. The image quality of cardiac PET/CT was evaluated by assessing the signal-to-noise ratio. CT-based coronary artery calcium quantification was performed using the Agatston scoring system.On the basis of our results, the CSCT protocols using tube currents of 50 and 150 mA should be able to achieve the lowest possible radiation dose while maintaining the desired image quality for normal-weight and mildly obese patients undergoing cardiac PET/CT examinations, respectively. When the proposed low-dose CSCT protocols were performed, radiation dose could be reduced by 83.34 and 50% compared with those from CSCT scans acquired with standard tube current settings for normal-weight and mildly obese patients, respectively. In the scanning of severely obese patients, an increase in tube voltage or current would help improve the reliability of image information provided by cardiac PET/CT.Our study demonstrated the feasibility of low-dose CT protocols for coronary artery calcium scoring and PET attenuation correction in cardiac PET/CT to examine patients in different weight categories. The calculations performed in this work should be able to provide practical information to achieve necessary diagnostic information while keeping radiation dose as low as reasonably achievable.
- Metatranscriptomics of N2-fixing cyanobacteria in the Amazon River plume. [JOURNAL ARTICLE]
- ISME J 2014 Dec 16.
Biological N2 fixation is an important nitrogen source for surface ocean microbial communities. However, nearly all information on the diversity and gene expression of organisms responsible for oceanic N2 fixation in the environment has come from targeted approaches that assay only a small number of genes and organisms. Using genomes of diazotrophic cyanobacteria to extract reads from extensive meta-genomic and -transcriptomic libraries, we examined diazotroph diversity and gene expression from the Amazon River plume, an area characterized by salinity and nutrient gradients. Diazotroph genome and transcript sequences were most abundant in the transitional waters compared with lower salinity or oceanic water masses. We were able to distinguish two genetically divergent phylotypes within the Hemiaulus-associated Richelia sequences, which were the most abundant diazotroph sequences in the data set. Photosystem (PS)-II transcripts in Richelia populations were much less abundant than those in Trichodesmium, and transcripts from several Richelia PS-II genes were absent, indicating a prominent role for cyclic electron transport in Richelia. In addition, there were several abundant regulatory transcripts, including one that targets a gene involved in PS-I cyclic electron transport in Richelia. High sequence coverage of the Richelia transcripts, as well as those from Trichodesmium populations, allowed us to identify expressed regions of the genomes that had been overlooked by genome annotations. High-coverage genomic and transcription analysis enabled the characterization of distinct phylotypes within diazotrophic populations, revealed a distinction in a core process between dominant populations and provided evidence for a prominent role for noncoding RNAs in microbial communities.The ISME Journal advance online publication, 16 December 2014; doi:10.1038/ismej.2014.240.
- Real-time MEG neurofeedback training of posterior alpha activity modulates subsequent visual detection performance. [JOURNAL ARTICLE]
- Neuroimage 2014 Dec 13.
It has been demonstrated that alpha activity is lateralized when attention is directed to the left or right visual hemifield. We investigated whether real-time neurofeedback training of the alpha lateralization enhances participants' ability to modulate posterior alpha lateralization and causes subsequent short-term changes in visual detection performance. The experiment consisted of three phases: (i) pre-training assessment, (ii) neurofeedback phase and (iii) post-training assessment. In the pre- and post-training phases we measured the threshold to covertly detect a cued faint Gabor stimulus presented in the left or right hemifield. During magnetoencephalography (MEG) neurofeedback, two face stimuli superimposed with noise were presented bilaterally. Participants were cued to attend to one of the hemifields. The transparency of the superimposed noise and thus the visibility of the stimuli was varied according to the momentary degree of hemispheric alpha lateralization. In a double-blind procedure half of the participants were provided with sham feedback. We found that hemispheric alpha lateralization increased with the neurofeedback training; this was mainly driven by an ipsilateral alpha increase. Surprisingly, comparing pre- to post-training, detection performance decreased for a Gabor stimulus presented in the hemifield that was un-attended during neurofeedback. This effect was not observed in the sham group. Thus, neurofeedback training alters alpha lateralization, which in turn decreases performances in the untrained hemifield. Our findings suggest that alpha oscillations play a causal role for the allocation of attention. Furthermore, our neurofeedback protocol serves to reduce the detection of unattended visual information and could therefore be of potential use for training to reduce distractibility in attention deficit patients, but also highlights that neurofeedback paradigms can have negative impact on behavioral performance and should be applied with caution.
- Assessing dynamic brain graphs of time-varying connectivity in fMRI data: Application to healthy controls and patients with schizophrenia. [JOURNAL ARTICLE]
- Neuroimage 2014 Dec 13.
Graph theory-based analysis has been widely employed in brain imaging studies, and altered topological properties of brain connectivity have emerged as important features of mental diseases such as schizophrenia. However, most previous studies have focused on graph metrics of stationary brain graphs, ignoring that brain connectivity exhibits fluctuations over time. Here we develop a new framework for accessing dynamic graph properties of time-varying functional brain connectivity in resting state fMRI data and apply it to healthy controls (HCs) and patients with schizophrenia (SZs). Specifically, nodes of brain graphs are defined by intrinsic connectivity networks (ICNs) identified by group independent component analysis (ICA). Dynamic graph metrics of the time-varying brain connectivity estimated by the correlation of sliding time-windowed ICA time courses of ICNs are calculated. First- and second-level connectivity states are detected based on the correlation of nodal connectivity strength between time-varying brain graphs. Our results indicate that SZs show decreased variance in the dynamic graph metrics. Consistent with prior stationary functional brain connectivity works, graph measures of identified first-level connectivity states show lower values in SZs. In addition, more first-level connectivity states are disassociated with the second-level connectivity state which resembles the stationary connectivity pattern computed by the entire scan. Collectively, the findings provide new evidence about altered dynamic brain graphs in schizophrenia which may underscore the abnormal brain performance in this mental illness.
- Subjective Assessment of Cochlear Implant Users' Signal-to-Noise Ratio Requirements for Different Levels of Wireless Device Usability. [JOURNAL ARTICLE]
- J Am Acad Audiol 2014 November/December; 25(10):952-968.
Background: In order to better inform the development and revision of the American National Standards Institute C63.19 and American National Standards Institute/Telecommunications Industry Association-1083 hearing aid compatibility standards, a previous study examined the signal strength and signal (speech)-to-noise (interference) ratio needs of hearing aid users when using wireless and cordless phones in the telecoil coupling mode. This study expands that examination to cochlear implant (CI) users, in both telecoil and microphone modes of use. Purpose: The purpose of this study was to evaluate the magnetic and acoustic signal levels needed by CI users for comfortable telephone communication and the users' tolerance relative to the speech levels of various interfering wireless communication-related noise types. Research Design: Design was a descriptive and correlational study. Simulated telephone speech and eight interfering noise types presented as continuous signals were linearly combined and were presented together either acoustically or magnetically to the participants' CIs. The participants could adjust the loudness of the telephone speech and the interfering noises based on several assigned criteria. Study Sample: The 21 test participants ranged in age from 23-81 yr. All used wireless phones with their CIs, and 15 also used cordless phones at home. There were 12 participants who normally used the telecoil mode for telephone communication, whereas 9 used the implant's microphone; all were tested accordingly. Data Collection and Analysis: A guided-intake questionnaire yielded general background information for each participant. A custom-built test control box fed by prepared speech-and-noise files enabled the tester or test participant, as appropriate, to switch between the various test signals and to precisely control the speech-and-noise levels independently. The tester, but not the test participant, could read and record the selected levels. Subsequent analysis revealed the preferred speech levels, speech (signal)-to-noise ratios, and the effect of possible noise-measurement weighting functions. Results: The participants' preferred telephone speech levels subjectively matched or were somewhat lower than the level that they heard from a 65 dB SPL wideband reference. The mean speech (signal)-to-noise ratio requirement for them to consider their telephone experience "acceptable for normal use" was 20 dB, very similar to the results for the hearing aid users of the previous study. Significant differences in the participants' apparent levels of noise tolerance among the noise types when the noise level was determined using A-weighting were eliminated when a CI-specific noise-measurement weighting was applied. Conclusions: The results for the CI users in terms of both preferred levels for wireless and cordless phone communication and signal-to-noise requirements closely paralleled the corresponding results for hearing aid users from the previous study, and showed no significant differences between the microphone and telecoil modes of use. Signal-to-noise requirements were directly related to the participants' noise audibility threshold and were independent of noise type when appropriate noise-measurement weighting was applied. Extending the investigation to include noncontinuous interfering noises and forms of radiofrequency interference other than additive audiofrequency noise could be areas of future study.