Intelligibility of chimeric locally time-reversed speech.

The intelligibility of chimeric locally time-reversed speech was investigated. Both (1) the boundary frequency between the temporally degraded band and the non-degraded band and (2) the segment duration were varied. Japanese mora accuracy decreased if the width of the degraded band or the segment duration increased. Nevertheless, the chimeric stimuli were more intelligible than the locally time-reversed controls. The results imply that the auditory system can use both temporally degraded speech information and undamaged speech information over different frequency regions in the processing of the speech signal, if the amplitude envelope in the frequency range of 840-1600 Hz was preserved.

Irrelevant speech effects with locally time-reversed speech: Native vs non-native language.

Irrelevant speech is known to interfere with short-term memory of visually presented items. Here, this irrelevant speech effect was studied with a factorial combination of three variables: the participants' native language, the language the irrelevant speech was derived from, and the playback direction of the irrelevant speech. We used locally time-reversed speech as well to disentangle the contributions of local and global integrity. German and Japanese speech was presented to German (n = 79) and Japanese (n = 81) participants while participants were performing a serial-recall task. In both groups, any kind of irrelevant speech impaired recall accuracy as compared to a pink-noise control condition. When the participants' native language was presented, normal speech and locally time-reversed speech with short segment duration, preserving intelligibility, was the most disruptive. Locally time-reversed speech with longer segment durations and normal or locally time-reversed speech played entirely backward, both lacking intelligibility, was less disruptive. When the unfamiliar, incomprehensible signal was presented as irrelevant speech, no significant difference was found between locally time-reversed speech and its globally inverted version, suggesting that the effect of global inversion depends on the familiarity of the language.

[Acute cholecystitis due to microscopic polyangiitis:a case report].

A 78-year-old man with chief complaints of cough and lower limb numbness was admitted to our hospital. Serum myeloperoxidase-antineutrophil cytoplasmic antibody titer (MPO-ANCA) was elevated (48.8U/ml), and a diagnosis of microscopic polyangiitis (MPA) was made. After admission, the patient developed a fever and right upper quadrant pain. Ultrasonography and computed tomography revealed an acute cholecystitis of unknown cause, and laparoscopic cholecystectomy was performed. Histopathological examination of the resected gallbladder revealed necrotizing vasculitis along with the infiltration of eosinophils, lymphocytes, and plasma cells around the small arteries in the muscular layer of the gallbladder, which are characteristics of MPA.

'Time-shrinking perception' in the visual system: a psychophysical and high-density ERP study.

'Time-shrinking perception (TSP)' is a unique perceptual phenomenon in which the duration of two successive intervals (T1 and T2) marked by three auditory stimuli is perceived as equal even when they are physically different. This phenomenon provides a link between time and working memory; however, previous studies have mainly been performed on the auditory modality but not the visual modality. To clarify the neural mechanism of visual TSP, we performed a psychophysical experiment and recorded event-related potentials (ERPs) under different T1/T2 combinations. Three successive black/white sinusoidal gratings (30 ms duration) were presented to the participants. In the psychophysical experiment, either T1 or T2 was varied from 240 to 560 ms in 40-ms steps, while T2 or T1 was fixed at 400 ms. Participants judged whether T1 and T2 were equal or not by pressing a button. ERPs were recorded from 128 scalp electrodes, while T1 was varied from 240, 320, and 400 ms with the 400 ms T2 duration, and vice versa. Behavioral data showed asymmetrical assimilation: When -80 ms ≤ (T1 - T2) ≤ +120 ms, TSP was observed in the T1-varied condition. When -120 ms ≤ (T1 - T2) ≤ +80 ms, it was also observed in the T2-varied condition. These asymmetric time ranges in vision were different from those in the auditory modality. ERP data showed that contingent negative variation (CNV) appeared in the fronto-central region at around 300-500 ms during T2 presentation in the T1 < T2 condition. In the /240/400/ pattern, the CNV amplitude was decreased at around 350 ms. In contrast, P3 appeared at the parietal region about 450-650 ms after T2 in the T1 > T2 condition. In the /400/240/ pattern, P3 amplitude was greater than those of other temporal patterns. These neural responses corresponded to participants' perception that T1 and T2 were not equal. The neural responses in the fronto-central region were involved with endogenous temporal attention for discrimination. Moreover, neural responses in the parietal region were engaged in exogenous temporal attention. Therefore, fronto-parietal neural responses underlie temporal perception in vision.

Memory disruption by irrelevant noise-vocoded speech: Effects of native language and the number of frequency bands.

To investigate the mechanisms by which unattended speech impairs short-term memory performance, speech samples were systematically degraded by means of a noise vocoder. For experiment 1, recordings of German and Japanese sentences were passed through a filter bank dividing the spectrum between 50 and 7000 Hz into 20 critical-band channels or combinations of those, yielding 20, 4, 2, or just 1 channel(s) of noise-vocoded speech. Listening tests conducted with native speakers of both languages showed a monotonic decrease in speech intelligibility as the number of frequency channels was reduced. For experiment 2, 40 native German and 40 native Japanese participants were exposed to speech processed in the same manner while trying to memorize visually presented sequences of digits in the correct order. Half of each sample received the German, the other half received the Japanese speech samples. The results show large irrelevant-speech effects increasing in magnitude with the number of frequency channels. The effects are slightly larger when subjects are exposed to their own native language. The results are neither predicted very well by the speech transmission index, nor by psychoacoustical fluctuation strength, most likely, since both metrics fail to disentangle amplitude and frequency modulations in the signals.

At what level is the gap transfer illusion illusory?

The gap transfer illusion is an auditory phenomenon in which a temporal gap in a longer glide transfers perceptually to a crossing shorter glide, making the longer glide illusorily continuous. This continuity is often considered a variation of classic illusory auditory continuity attributed to auditory peripheral activity, but a new view is given here supported by a series of sound demonstrations indicating that this illusory continuity is purely caused by a higher mechanism of perceptual organization.

Measures of music-like experience emergent in a sonic Ganzfeld: An example of perceptual structuring on the edge of silence.

We conducted an experiment in which participants listened to a semi-stochastic stream of acoustic data, during which they reported regular variations in melody, pitch and rhythm that are not physically present in the stimulus. In addition, the occurrence of particular forms (melodies and rhythms) and pitches appear to be associated with the occurrence of others. This indicates that a complex taxonomy of subjective auditory experience can be evoked in observers given small variation in the quality of noise along the auditory spectrum. It also strongly indicates that when experiencing "noise," our automatic response is to restructure this such that it becomes "perceptually" meaningful. In an environment where there is no sound, neural systems will reduce their engagement, and will respond semi stochastically. Taken alongside our data, this tends to suggest that one consequence of "silence" might be a tendency to spontaneously hallucinate complex and well-structured auditory experience based solely upon the stochastic neural response to the absence of sound. This paper describes the type of experience one might have on the "edge of silence" and discusses some of the associated implications.

Assessment of substrate inhibition of bacterial oligopeptidase B.

Oligopeptidase B (OPB; EC 3.4.21.83) from 2 Gram-negative bacteria, Stenotrophomonas maltophilia (Stm) and Serratia marcescens (Sem), and the Gram-positive bacterium Rhodococcus erythropolis (Re) were cloned and characterized to clarify their activities and substrate specificities using peptidyl-MCA substrates containing Arg or Lys. The cloned enzymes, Stm, Sem and ReOPBs, in addition to Escherichia coli OPB (EcOPB) were expressed using a pET expression system. Although the Stm and SemOPBs share 45% sequence identity to each other and up to 60% identity with respect to their catalytic domains, their activities towards MCA substrates were quite different. StmOPB is approximately 100-500 times more active than SemOPB and 3-30 times more active than EcOPB. The activity of ReOPB is comparable to that of StmOPB and it shares 40% and 36% identity to StmOPB and SemOPB, respectively. Some features of Stm, Re and EcOPBs are similar to those of previously cloned OPBs, which were also strongly inhibited by substrates, but SemOPB differs from all other OPBs in that it is not inhibited by substrates; even substrates containing double arginine at 35 µM did not inhibit SemOPB. On the other hand, the same substrates at only 5 µM inhibited the activity of the Stm, Re, and EcOPB. This phenomenon was not observed with substrates containing single or double lysine.

Roles of temporal proximity between sound edges in the perceptual organization of veridical and illusory auditory events.

The gap transfer illusion is an auditory illusion in which a temporal gap in a long glide is perceived as if it had transferred to a physically continuous shorter glide. The illusion typically occurs when the long and the shorter glide cross each other at their temporal midpoints, where the long glide is physically divided by the gap. The occurrence of the gap transfer illusion was investigated in stimuli in which the duration and the slope of the long glide were 5000 ms and ∼0.8 oct/s. The shorter glide was given different frequency ranges and different temporal ranges, and thus its time-frequency slope was also varied. The overlap configuration of these crossing glides was varied as well. As control stimuli, we used stimuli in which a continuous long glide crossed a shorter glide with a gap, i.e., the opposite configuration of the gap-transfer stimuli as above, as well as stimuli in which both crossing glides were continuous. The perception of two crossing tones tended to be facilitated when the glides differed in duration and/or slope. When the glides were relatively similar in duration and slope, however, bouncing percepts appeared more often. Similarity between the crossing tones thus promoted auditory bouncing, while dissimilarity between them facilitated the crossing percept. If the crossing percept dominated in gap-transfer stimuli, the gap transfer illusion took place in a typical manner, but the illusory transfer of the gap could occur even when the crossing percept was not dominant. When the shorter glide was as short as 500 ms, the crossing percept and the gap transfer illusion were robust. The mechanism of the illusion was examined in terms of factors that can influence the perceptual integration of auditory stimulus edges, i.e., onsets and offsets, of physically different sounds. Much like the perceptual construction of speech units, we suggest that the auditory system utilizes a rough time window of several hundreds of milliseconds to construct an initial skeleton percept of auditory events. The present data indicated the importance of the temporal proximity, rather than the frequency proximity, between sound edges in the illusory tone construction.

The common limitations in auditory temporal processing for Mandarin Chinese and Japanese.

The present investigation focused on how temporal degradation affected intelligibility in two types of languages, i.e., a tonal language (Mandarin Chinese) and a non-tonal language (Japanese). The temporal resolution of common daily-life sentences spoken by native speakers was systematically degraded with mosaicking (mosaicising), in which the power of original speech in each of regularly spaced time-frequency unit was averaged and temporal fine structure was removed. The results showed very similar patterns of variations in intelligibility for these two languages over a wide range of temporal resolution, implying that temporal degradation crucially affected speech cues other than tonal cues in degraded speech without temporal fine structure. Specifically, the intelligibility of both languages maintained a ceiling up to about the 40-ms segment duration, then the performance gradually declined with increasing segment duration, and reached a floor at about the 150-ms segment duration or longer. The same limitations for the ceiling performance up to 40 ms appeared for the other method of degradation, i.e., local time-reversal, implying that a common temporal processing mechanism was related to the limitations. The general tendency fitted to a dual time-window model of speech processing, in which a short (~ 20-30 ms) and a long (~ 200 ms) time-window run in parallel.

How Pause Duration Influences Impressions of English Speech: Comparison Between Native and Non-native Speakers.

The purpose of this study was to investigate how the subjective impression of English speech would change when pause duration at punctuation marks was varied. Two listening experiments were performed in which written English speech segments were rated on a variety of evaluation items by both native-English speakers and non-native speakers (native-Chinese speakers and native-Japanese speakers). The ratings were then subjected to factor analysis. In the first experiment, the pauses in three segments were made into the same durations, from 0.075 to 4.8 s. Participants rated the segments on 23 evaluation items on a rating scale from 1 to 10. A varimax rotation after PCA (principal component analysis) led to two factors that were related to speech style. These two factors could be interpreted as representing speech naturalness and speech rate. Speech segments with a pause duration of 0.6 s received the highest naturalness evaluation, while perceived speech rate decreased as the physical pause duration increased, without any changes in utterance segments. In the second experiment, a full-factorial design of pause durations (0.15, 0.3, 0.6, 1.2, and 2.4 s) within and between sentences, i.e., for commas and for periods, was implemented in two speech segments. The original speech segments and speech segments without any pauses were also included as control conditions. From ratings on 12 evaluation items, similar to Experiment 1, two factors representing speech naturalness and speech rate were obtained. The results showed again that the perceived speech rate decreased with an increase only in pause duration. As for speech naturalness, the highest evaluations occurred when pause durations were 0.6 s within sentences, and either 0.6 or 1.2 s between sentences. This recommends fixing all pause durations to 0.6 s as a practical way to train non-native speakers to make their spoken English appear more natural.

Identification of the active site and characterization of a novel sporulation-specific cysteine protease YabG from Bacillus subtilis.

In order to characterize the probable protease gene yabG found in the genomes of spore-forming bacteria, Bacillus subtilis yabG was expressed as a 35 kDa His-tagged protein (BsYabG) inEscherichia coli cells. During purification using Ni-affinity chromatography, the 35 kDa protein was degraded via several intermediates to form a 24 kDa protein. Furthermore, it was degraded after an extended incubation period. The effect of protease inhibitors, including certain chemical modification reagents, on the conversion of the 35 kDa protein to the 24 kDa protein was investigated. Reagents reacting with sulphhydryl groups exerted significant effects strongly suggesting that the yabG gene product is a cysteine protease with autolytic activity. Site-directed mutagenesis of the conserved Cys and His residues indicated that Cys218 and His172 are active site residues. No degradation was observed in the C218A/S and H172A mutants. In addition to the chemical modification reagents, benzamidine inhibitedGraphical Abstract the degradation of the 24 kDa protein. Determination of the N-terminal amino acid sequences of the intermediates revealed trypsin-like specificity for YabG protease. Based on the relative positions of His172 and Cys218 and their surrounding sequences, we propose the classification of YabG as a new family of clan CD in the MEROPS peptidase database.

Perceived Congruency in Audiovisual Stimuli Consisting of Gabor Patches and AM and FM Tones.

Experiments that focus on how humans perceive temporal, spatial or synaesthetic congruency in audiovisual sensory information have often employed stimuli consisting of a Gabor patch and an amplitude (AM) or frequency (FM)-modulated sound. Introducing similarity between the static and dynamic features of the Gabor patch and the (carrier) frequency or modulation frequency of the sound is often assumed to be effective enough to induce congruency. However, comparative empirical data on perceived congruency of various stimulus parameters are not readily available, and in particular with respect to sound modulation, it is still not clear which type (AM or FM) induces perceived congruency best in tandem with various patch parameters. In two experiments, we examined Gabor patches of various spatial frequencies with flickering (2, 3 and 4 flickers/s) or drifting (0.5, 1.0 and 1.5 degrees/s) gratings in combinations with AM or FM tones of 2-, 3- and 4-Hz modulation and 500-, 1000- and 2000-Hz carrier frequencies. Perceived congruency ratings were obtained by asking participants to rate stimulus (in)congruency from 1 (incongruent) to 7 (congruent). The data showed that varying the spatial frequency of the Gabor patch and the carrier frequency of the modulated tone had comparatively little impact on perceived congruency. Similar to previous findings, similarity between the temporal frequency of the Gabor patch and the modulated tone effectively promoted perceived congruency. Furthermore, direct comparisons convincingly showed that AM tones in combination with flickering Gabor patches received significantly higher audiovisual congruency ratings compared to FM tones.

Structure of aminopeptidase N from Escherichia coli complexed with the transition-state analogue aminophosphinic inhibitor PL250.

Aminopeptidase N (APN; EC 3.4.11.2) purified from Escherichia coli has been crystallized with the optically pure aminophosphinic inhibitor PL250, H(3)N(+)-CH(CH(3))-P(O)(OH)-CH(2)-CH(CH(2)Ph)-CONH-CH(CH(2)Ph)CO(2)(-), which mimics the transition state of the hydrolysis reaction. PL250 inhibits APN with a K(i) of 1.5-2.2 nM and its three-dimensional structure in complex with E. coli APN showed its interaction with the S(1), S'(1) and S'(2) subsites of the catalytic site. In this structure, the Zn ion was shown to be pentacoordinated by His297, His301 and Glu320 of APN and the two O atoms of the phosphinic moiety of PL250. One of these O atoms is also involved in a hydrogen bond to Tyr381, supporting the proposed role of this amino acid in the stabilization of the transition state of the enzymatic process. The strength of the phosphinic zinc binding and the occupancy of the S'(2) subsite account for the 100-fold increase in affinity of PL250 compared with the dipeptide-derived inhibitor bestatin (K(i) = 4.1 x 10(-6) M). Accordingly, the removal of the C-terminal phenylalanine of PL250 resulted in a large decrease in affinity (K(i) = 2.17 x 10(-7) M). Furthermore, it was observed that the C-terminal carboxyl group of the inhibitor makes no direct interactions with the amino acids of the APN active site. Interestingly, PL250 exhibits the same inhibitory potency for E. coli APN and for mammalian enzymes, suggesting that the structure of the complex could be used as a template for the rational design of various human APN inhibitors needed to study the role of this aminopeptidase in various pathologies.

Dipeptidyl aminopeptidase IV from Stenotrophomonas maltophilia exhibits activity against a substrate containing a 4-hydroxyproline residue.

The crystal structure of dipeptidyl aminopeptidase IV from Stenotrophomonas maltophilia was determined at 2.8-A resolution by the multiple isomorphous replacement method, using platinum and selenomethionine derivatives. The crystals belong to space group P4(3)2(1)2, with unit cell parameters a = b = 105.9 A and c = 161.9 A. Dipeptidyl aminopeptidase IV is a homodimer, and the subunit structure is composed of two domains, namely, N-terminal beta-propeller and C-terminal catalytic domains. At the active site, a hydrophobic pocket to accommodate a proline residue of the substrate is conserved as well as those of mammalian enzymes. Stenotrophomonas dipeptidyl aminopeptidase IV exhibited activity toward a substrate containing a 4-hydroxyproline residue at the second position from the N terminus. In the Stenotrophomonas enzyme, one of the residues composing the hydrophobic pocket at the active site is changed to Asn611 from the corresponding residue of Tyr631 in the porcine enzyme, which showed very low activity against the substrate containing 4-hydroxyproline. The N611Y mutant enzyme was generated by site-directed mutagenesis. The activity of this mutant enzyme toward a substrate containing 4-hydroxyproline decreased to 30.6% of that of the wild-type enzyme. Accordingly, it was considered that Asn611 would be one of the major factors involved in the recognition of substrates containing 4-hydroxyproline.

Ascaris suum cytochrome b5, an adult-specific secretory protein reducing oxygen-avid ferric hemoglobin.

The anaerobic parasitic nematode Ascaris suum has an oxygen-avid hemoglobin in the perienteric fluid, the biological function of which remains elusive. Here, we report that Ascaris cytochrome b5 is expressed specifically in the intestinal parasitic stage and is secreted into the perienteric fluid, thus co-localizing with Ascaris hemoglobin. We also found that cytochrome b5 reduces Ascaris non-functioning ferric methemoglobin more efficiently than mammalian methemoglobin. Furthermore, a computer graphics model of the electron transfer complex between Ascaris cytochrome b5 and Ascaris hemoglobin strongly suggested that these two proteins are physiological redox partners. Nitric oxide has been reported to react easily with oxygen captured in hemoglobin to form nitrate, but not toxic free radicals, which may result in production of methemoglobin for the cytochrome b5 to regenerate functional ferrous hemoglobin. Therefore, our findings suggest that Ascaris cytochrome b5 is a key redox partner of Ascaris hemoglobin, which acts as an antioxidant.

Frequency modulation facilitates (modal) auditory restoration of a gap.

In this study we further investigated processes of auditory restoration (AR) in recently described stimulus types: the so-called gap-transfer stimulus, the shared-gap stimulus and the pseudo-continuous stimulus. The stimuli typically consist of two crossing sounds of unequal duration. In the shared-gap and pseudo-continuous stimuli, the two crossing sounds share a gap (<45 ms) at their crossing point. In the gap-transfer stimulus, only the long sound contains a gap (100 ms), whereas the short sound is physically continuous. Earlier research has shown that in these stimuli the long sound is subject to AR, in spite of the gap it contains, whereas the gap is perceived in the short sound. Experiment 1 of the present study showed that AR of the stimuli's long sound was facilitated when its slope increased from 0 to 1 oct/s. Experiment 2 showed that the effect of slope on AR of the long sound also occurred when the slope relationship between the long and short sound was fixed. Implications for a tentative sound edge-binding explanation of AR as well as alternative explanations for the effect of slope on AR are discussed.

Frequency specificity of amplitude envelope patterns in noise-vocoded speech.

We examined the frequency specificity of amplitude envelope patterns in 4 frequency bands, which universally appeared through factor analyses applied to power fluctuations of critical-band filtered speech sounds in 8 different languages/dialects [Ueda and Nakajima (2017). Sci. Rep., 7 (42468)]. A series of 3 perceptual experiments with noise-vocoded speech of Japanese sentences was conducted. Nearly perfect (92-94%) mora recognition was achieved, without any extensive training, in a control condition in which 4-band noise-vocoded speech was employed (Experiments 1-3). Blending amplitude envelope patterns of the frequency bands, which resulted in reducing the number of amplitude envelope patterns while keeping the average spectral levels unchanged, revealed a clear deteriorating effect on intelligibility (Experiment 1). Exchanging amplitude envelope patterns brought generally detrimental effects on intelligibility, especially when involving the 2 lowest bands (≲1850 Hz; Experiment 2). Exchanging spectral levels averaged in time had a small but significant deteriorating effect on intelligibility in a few conditions (Experiment 3). Frequency specificity in low-frequency-band envelope patterns thus turned out to be conspicuous in speech perception.

Temporal Resolution Needed for Auditory Communication: Measurement With Mosaic Speech.

Temporal resolution needed for Japanese speech communication was measured. A new experimental paradigm that can reflect the spectro-temporal resolution necessary for healthy listeners to perceive speech is introduced. As a first step, we report listeners' intelligibility scores of Japanese speech with a systematically degraded temporal resolution, so-called "mosaic speech": speech mosaicized in the coordinates of time and frequency. The results of two experiments show that mosaic speech cut into short static segments was almost perfectly intelligible with a temporal resolution of 40 ms or finer. Intelligibility dropped for a temporal resolution of 80 ms, but was still around 50%-correct level. The data are in line with previous results showing that speech signals separated into short temporal segments of <100 ms can be remarkably robust in terms of linguistic-content perception against drastic manipulations in each segment, such as partial signal omission or temporal reversal. The human perceptual system thus can extract meaning from unexpectedly rough temporal information in speech. The process resembles that of the visual system stringing together static movie frames of ~40 ms into vivid motion.

D-3-hydroxybutyrate dehydrogenase from Pseudomonas fragi: molecular cloning of the enzyme gene and crystal structure of the enzyme.

The gene coding for d-3-hydroxybutyrate dehydrogenase (HBDH) was cloned from Pseudomonas fragi. The nucleotide sequence contained a 780 bp open reading frame encoding a 260 amino acid residue protein. The recombinant enzyme was efficiently expressed in Escherichia coli cells harboring pHBDH11 and was purified to homogeneity as judged by SDS-PAGE. The enzyme showed a strict stereospecificity to the D-enantiomer (3R-configuration) of 3-hydroxybutyrate as a substrate. Crystals of the ligand-free HBDH and of the enzyme-NAD+ complex were obtained using the hanging-drop, vapor-diffusion method. The crystal structure of the HBDH was solved by the multiwavelength anomalous diffraction method using the SeMet-substituted enzyme and was refined to 2.0 A resolution. The overall structure of P.fragi HBDH, including the catalytic tetrad of Asn114, Ser142, Tyr155, and Lys159, shows obvious relationships with other members of the short-chain dehydrogenase/reductase (SDR) family. A cacodylate anion was observed in both the ligand-free enzyme and the enzyme-NAD+ complex, and was located near the catalytic tetrad. It was shown that the cacodylate inhibited the NAD+-dependent D-3-hydroxybutyrate dehydrogenation competitively, with a Ki value of 5.6 mM. From the interactions between cacodylate and the enzyme, it is predicted that substrate specificity is achieved through the recognition of the 3-methyl and carboxyl groups of the substrate.