Pitch related to spectral edges of broadband signals.

A complex tone often evokes a pitch sensation associated with its extreme spectral components, besides the holistic pitch associated with its fundamental frequency. We studied the edge pitch created at the upper spectral edge of complexes with a low-pass spectrum by asking subjects to adjust the frequency of a sinusoidal comparison tone to the perceived pitch. Measurements were performed for different values of the fundamental frequency and of the upper frequency of the complex as well as for three different phase relations of the harmonic components. For a wide range of these parameters the subjects could adjust the comparison tone with a high accuracy, measured as the standard deviation of repeated adjustments, to a frequency close to the nominal edge frequency. The detailed dependence of the matching accuracy on temporal parameters of the harmonic complexes suggests that the perception of the edge pitch in harmonic signals is related to the temporal resolution of the hearing system. This resolution depends primarily on the time constants of basilar-membrane filters and on additional limitations due to neuronal processes.     

Empirical mode decomposition of field potentials from macaque V4 in visual spatial attention

Empirical mode decomposition (EMD) has recently been introduced as a local and fully data-driven technique for the analysis of non-stationary time-series. It allows the frequency and amplitude of a time-series to be evaluated with excellent time resolution. In this article we consider the application of EMD to the analysis of neuronal activity in visual cortical area V4 of a macaque monkey performing a visual spatial attention task. We show that, by virtue of EMD, field potentials can be resolved into a sum of intrinsic components with different degrees of oscillatory content. Low-frequency components in single-trial recordings contribute to the average visual evoked potential (AVEP), whereas high-frequency components do not, but are identified as gamma-band (30–90 Hz) oscillations. The magnitude of time-varying gamma activity is shown to be enhanced when the monkey attends to a visual stimulus as compared to when it is not attending to the same stimulus. Comparison with Fourier analysis shows that EMD may offer better temporal and frequency resolution. These results support the idea that the magnitude of gamma activity reflects the modulation of V4 neurons by visual spatial attention. EMD, coupled with instantaneous frequency analysis, is demonstrated to be a useful technique for the analysis of neurobiological time-series.     

Basic auditory processes involved in the analysis of speech sounds

This paper reviews the basic aspects of auditory processing that play a role in the perception of speech. The frequency selectivity of the auditory system, as measured using masking experiments, is described and used to derive the internal representation of the spectrum (the excitation pattern) of speech sounds. The perception of timbre and distinctions in quality between vowels are related to both static and dynamic aspects of the spectra of sounds. The perception of pitch and its role in speech perception are described. Measures of the temporal resolution of the auditory system are described and a model of temporal resolution based on a sliding temporal integrator is outlined. The combined effects of frequency and temporal resolution can be modelled by calculation of the spectro-temporal excitation pattern, which gives good insight into the internal representation of speech sounds. For speech presented in quiet, the resolution of the auditory system in frequency and time usually markedly exceeds the resolution necessary for the identification or discrimination of speech sounds, which partly accounts for the robust nature of speech perception. However, for people with impaired hearing, speech perception is often much less robust.     

A New Test of Attention in Listening (TAIL) Predicts Auditory Performance

Attention modulates auditory perception, but there are currently no simple tests that specifically quantify this modulation. To fill the gap, we developed a new, easy-to-use test of attention in listening (TAIL) based on reaction time. On each trial, two clearly audible tones were presented sequentially, either at the same or different ears. The frequency of the tones was also either the same or different (by at least two critical bands). When the task required same/different frequency judgments, presentation at the same ear significantly speeded responses and reduced errors. A same/different ear (location) judgment was likewise facilitated by keeping tone frequency constant. Perception was thus influenced by involuntary orienting of attention along the task-irrelevant dimension. When information in the two stimulus dimensions were congruent (same-frequency same-ear, or different-frequency different-ear), response was faster and more accurate than when they were incongruent (same-frequency different-ear, or different-frequency same-ear), suggesting the involvement of executive control to resolve conflicts. In total, the TAIL yielded five independent outcome measures: (1) baseline reaction time, indicating information processing efficiency, (2) involuntary orienting of attention to frequency and (3) location, and (4) conflict resolution for frequency and (5) location. Processing efficiency and conflict resolution accounted for up to 45% of individual variances in the low- and high-threshold variants of three psychoacoustic tasks assessing temporal and spectral processing. Involuntary orientation of attention to the irrelevant dimension did not correlate with perceptual performance on these tasks. Given that TAIL measures are unlikely to be limited by perceptual sensitivity, we suggest that the correlations reflect modulation of perceptual performance by attention. The TAIL thus has the power to identify and separate contributions of different components of attention to auditory perception.     

Examination of the secondary structure of proteins by deconvolved FTIR spectra

Fourier transform ir (FTIR) spectra of 21 globular proteins have been obtained at 2 cm^?1 resolution from 1600 to 1700 cm^?1 in deuterium oxide solution. Fourier self-deconvolution was applied to all spectra, revealing that the amide I band of each protein except casein consists of six to nine components. The components are observed at 11 well-defined frequencies, although all proteins do not exhibit components at every characteristic frequency. The root mean square (RMS) deviation of 124 individual values from the 11 average characteristic frequencies is 1.9 cm^?1. The observed components are assigned to helical segments, extended beta-segments, unordered segments, and turns. Segments with similar structures do not necessarily exhibit band components with identical frequencies. For instance, the lower frequency beta-structure band can vary within a range of approximately 15 cm^?1. The relative areas of the individual components of the deconvolved spectra were determined by a Gauss–Newton, iterative curve-fitting procedure that assumed Gaussian band envelopes for the deconvolved components. The measured areas were used to estimate the percentage of helix and beta-structure for each of 21 globular proteins. The results are in good general agreement with values derived from x-ray data by Levitt and Greer. The RMS deviation between 22 values (alpha- and beta-content of 11 beta-rich proteins measured by both techniques) is 2.5 percentage points; the maximum absolute deviation is 4 percentage points.     

Heart energy signature spectrogram for cardiovascular diagnosis

A new method and application is proposed to characterize intensity and pitch of human heart sounds and murmurs. Using recorded heart sounds from the library of one of the authors, a visual map of heart sound energy was established. Both normal and abnormal heart sound recordings were studied. Representation is based on Wigner-Ville joint time-frequency transformations. The proposed methodology separates acoustic contributions of cardiac events simultaneously in pitch, time and energy. The resolution accuracy is superior to any other existing spectrogram method. The characteristic energy signature of the innocent heart murmur in a child with the S3 sound is presented. It allows clear detection of S1, S2 and S3 sounds, S2 split, systolic murmur, and intensity of these components. The original signal, heart sound power change with time, time-averaged frequency, energy density spectra and instantaneous variations of power and frequency/pitch with time, are presented. These data allow full quantitative characterization of heart sounds and murmurs. High accuracy in both time and pitch resolution is demonstrated. Resulting visual images have self-referencing quality, whereby individual features and their changes become immediately obvious.     

A comparison of deconvolution techniques for stress relaxation

Stress relaxation (or equivalently creep) allows a large range of the relaxation (retardation) spectrum of materials to be examined, particularly at lower frequencies. However, higher frequency components of the relaxation curves (typically of the order of Hertz) are attenuated due to the finite time taken to strain the specimen. This higher frequency information can be recovered by deconvolution of the stress and strain during the loading period. This paper examines the use of three separate deconvolution techniques: numerical (Fourier) deconvolution, semi-analytical deconvolution using a theoretical form of the strain, and deconvolution by a linear approximation method. Both theoretical data (where the exact form of the relaxation function is known) and experimental data were used to assess the accuracy and applicability of the deconvolution methods. All of the deconvolution techniques produced a consistent improvement in the higher frequency data up to the frequencies of the order of Hertz, with the linear approximation method showing better resolution in high-frequency analysis of the theoretical data. When the different deconvolution techniques were applied to experimental data, similar results were found for all three deconvolution techniques. Deconvolution of the stress and strain during loading is a simple and practical method for the recovery of higher frequency data from stress-relaxation experiments.     

Resonant modes and musical ratios in otoacoustic emissions

The ratios between frequency components of evoked otoacoustic emissions (OAE) were investigated for 100 ears. The signals were decomposed by means of an adaptive approximation method into basic waveforms coming from a very large and redundant dictionary of Gabor functions. The high time-frequency resolution of the method and the parametric representation of the waveforms allowed for an estimation of the frequency ratios of the basic components. A repetitive occurrence of the “fifths”, “fourths” and octaves connected with the Pythagorean temperament was found. The octaves containing “fifths” were identified. This kind of sequences in OAE tend to appear in the same form for tonal stimulations of different frequencies and for broadband stimuli. The significance of the results was confirmed by comparison to Monte Carlo simulations of the null hypothesis of random distribution of frequency modes. These findings support the resonance theory of hearing, which binds musical ratios with the geometrical spacing of outer hair cells in the cochlea.     

Spectral analysis of magnetic fields from domestic appliances and corresponding induced current densities in an anatomically based model of the human head

Magnetic fields emitted by electric appliances such as razors, hair dryers, and drills were measured in the frequency domain. Results show the presence of high-frequency components (up to 96 kHz for razors, up to 3.4 kHz for hair dryers, and up to 8.6 kHz for drills) in the harmonic content of the fields. The measured fields were used to calculate the induced current densities in an anatomically based model of the human head (resolution 1.31 cm) by using the impedance method. The harmonic field contribution to the current density was higher than that from the carrier frequency for all the tested appliances. © 1995 Wiley-Liss, Inc.     

A basic study on universal design of auditory signals in automobiles

In this paper, the impression of various kinds of auditory signals currently used in automobiles and a comprehensive evaluation were measured by a semantic differential method. The desirable acoustic characteristic was examined for each type of auditory signal. Sharp sounds with dominant high-frequency components were not suitable for auditory signals in automobiles. This trend is expedient for the aged whose auditory sensitivity in the high frequency region is lower. When intermittent sounds were used, a longer OFF time was suitable. Generally, "dull (not sharp)" and "calm" sounds were appropriate for auditory signals. Furthermore, the comparison between the frequency spectrum of interior noise in automobiles and that of suitable sounds for various auditory signals indicates that the suitable sounds are not easily masked. The suitable auditory signals for various purposes is a good solution from the viewpoint of universal design.     

Application of the Gabor Transform for Analysis of Electromyographic Signals of the Intestine in the Low-Frequency Region

The Gabor transform allows quantitative estimation of the non-stationarity of the electromyographic signal in the low-frequency region with the maxim permissible time–frequency resolution. The calculation of the parameters of the Gabor transform was conducted on different time and frequency intervals to estimate the slow-wave activity of the intestine. It was demonstrated that the efficient size of the 32-s time window, which provides the efficient resolution of the frequency spectrum at 0.01 Hz, is suitable for the accurate study of the change in the frequency of slow waves. The ability to construct the dependence of the change in the frequency of slow waves of electromyograms on time with the specified accuracy was demonstrated.     

基于频域反卷积滤波器的光声成像

采用探测器的脉冲响应在频域反卷积滤波光声信号以进一步提高光声成像的分辨率.由仿真和实验结果表明,频域反卷积滤波重建相对于时域反投影重建和滤波反投影重建具有更好的成像效果,明显地提高重建图像的分辨率,经仿真结果的计算,其重建图像的分辨率由2.58 mm提高到了0.16 mm.实验所用的光源为YAG激光器,波长为1064 ...     

Energy transfer processes in Gloeobacter violaceus PCC 7421 that possesses phycobilisomes with a unique morphology

We examined energy transfer dynamics in phycobilisomes (PBSs) of cyanobacteria in relation to the morphology and pigment compositions of PBSs. We used Gloeobacter violaceus PCC 7421 and measured time-resolved fluorescence spectra in three types of samples, i.e., intact cells, PBSs, and rod assemblies separated from cores. Fremyella diplosiphon, a cyanobacterial species well known for its complementary chromatic adaptation, was used for comparison after growing under red or green light. Spectral data were analyzed by the fluorescence decay-associated spectra with components common in lifetimes with a time resolution of 3 ps/channel and a spectral resolution of 2 nm/channel. This ensured a higher resolution of the energy transfer kinetics than those obtained by global analysis with fewer sampling intervals. We resolved four spectral components in phycoerythrin (PE), three in phycocyanin (PC), two in allophycocyanin, and two in photosystem II. The bundle-like PBSs of G. violaceus showed multiple energy transfer pathways; fast ( approximately 10 ps) and slow ( approximately 100 ps and approximately 500 ps) pathways were found in rods consisting of PE and PC. Energy transfer time from PE to PC was two times slower in G. violaceus than in F. diplosiphon grown under green light.     

Use of UV excitation in confocal laser scanning fluorescence microscopy

By making only minor modifications, we adapted a conventional confocal beam-scanning laser microscope for the recording of UV-excited fluorescence. The major, and most expensive, change is that we coupled an external UV argon ion laser, providing the wavelengths 334, 351 and 364 nm, to the microscope scanner. We also replaced some optical components to obtain improved transmission and reflection properties in the UV. Only easily obtainable and inexpensive off-the-shelf components were used. The most serious problem encountered was the chromatic aberration of the microscope objective when using both UV and visible wavelengths. This is of no consequence in conventional microscopy where good imaging properties are important only in the visible region. In confocal microscopy on the other hand, good imaging properties are necessary for both the exciting and fluorescent light. Rather than having new optics designed, we tried with simple means to reduce the effects of the chromatic aberration to a tolerable level. This was done by mechanical adjustments in the ray-path. In addition we also tested two mirror objectives, which are inherently free from chromatic aberrations. However, such objectives have rather limited numerical apertures and are not of the immersion type. Their value in biomedical applications is therefore limited.The objective most frequently used in our experiments was a 63/1.25 oil-immersion fluorite. Without any compensation this objective had a depth resolution in UV-excited confocal fluorescence that was an order of magnitude worse than when using visible-light excitation. The useful field of view was also very small due to lateral chromatic aberration. By simple means we managed to improve the depth resolution by a factor of 4.4, and at the same time increase the useful field of view substantially. Still, the depth resolution was worse than what is obtained using visible light excitation. We think this is due to the fact that after compensation the objective is working with an incorrect tube length.Using the modified instrument, we recorded specimens labelled with AMCA and Fluoro-Gold, obtaining 1.5 μm thick optical sections.     

New methods for rapid separation and detection of oligosaccharides from glycoproteins

Ion exchange chromatography at high pH with pulsed amperometric detection of the eluted glycans permitted resolution of the eight major components in the mixture of asparagine-linked glycans derived from the single glycosylation site of ovalbumin. The individual glycans were first partially separated according to size, and were characterized by fast atom bombardment-mass spectrometry and specific enzymatic degradation with beta-galactosidase and endoglycosidase H; subnanomolar quantities of all eight components could subsequently be unequivocally identified in the elution diagram. To ascertain that the chromatographic separation of the ovalbumin glycan mixture was not restricted to the asparagine-linked glycans, it was established that the corresponding mixture of reducing oligosaccharides (asparagine removed) or Asn-oligosaccharides blocked at the alpha-amino group with biotin gave very similar resolution of the eight glycans. In the absence of pure reference compounds, the quantification of the different glycans by the amperometric detection system was evaluated by comparing the electrochemical signal to the molecular ion peak intensity in the mass spectrometer. With one exception, the two methods were in good agreement, which suggests that the amperometric detection system yields a valid quantitative estimate for most of these chemically related compounds.     

Frequency resolution and spectral integration (critical band analysis) in single units of the cat primary auditory cortex

Frequency resolution and spectral filtering in the cat primary auditory cortex (AI) were mapped by extracellular recordings of tone responses in white noise of various bandwidths. Single-tone excitatory tuning curves, critical bandwidths, and critical ratios were determined as a function of neuronal characteristic frequency and tone level. Single-tone excitatory tuning curves are inadequate measures of frequency resolution and spectral filtering in the AI, because their shapes (in most neurons) deviated substantially from the shapes of “tuning curves for complex sound analysis”, the curves determined by the band limits of the critical bandwidths. Perceptual characteristics of spectral filtering (intensity independence and frequency dependence) were found in average critical bandwidths of neurons from the central and ventral AI. The highest frequency resolution (smallest critical bandwidths) reached by neurons in the central and ventral AI equaled the psychophysical frequency resolution. The dorsal AI is special, since most neurons there had response properties incompatible with psychophysical features of frequency resolution. Perceptual characteristics of critical ratios were not found in the average neuronal responses in any area of the AI. It seems that spectral integration in the way proposed to be the basis for the perception of tones in noise is not present at the level of the AI. Accepted: 21 July 1997     

Songbird frequency selectivity and temporal resolution vary with sex and season

Many species of songbirds exhibit dramatic seasonal variation in song output. Recent evidence suggests that seasonal changes in auditory processing are coincident with seasonal variation in vocal output. Here, we show, for the first time, that frequency selectivity and temporal resolution of the songbird auditory periphery change seasonally and in a sex-specific manner. Male and female house sparrows (Passer domesticus) did not differ in their frequency sensitivity during the non-breeding season, nor did they differ in their temporal resolution. By contrast, female house sparrows showed enhanced frequency selectivity during the breeding season, which was matched by a concomitant reduction of temporal resolution. However, males failed to show seasonal plasticity in either of these auditory properties. We discuss potential mechanisms generating these seasonal patterns and the implications of sex-specific seasonal changes in auditory processing for vocal communication.     

Methods for the identification of evoked response components in the frequency and combined time/frequency domains

Two prominent frequency components designated f1 and f2 have been identified in the visual evoked response to the transient presentation of sinusoidal luminance gratings in the range of 0.5–8 c/deg. The components occur at temporal frequencies below the alpha band, with the f1 frequency roughly half that of the f2 frequency. The f1 component is largest at low spatial frequencies with f2 becoming progressively dominant as spatial frequency is increased.The frequency and amplitude of f1 and f2 change substantially over the time course of the response. This has been studied by calculating the temporal frequency spectrum of the transient evoked potential over successive short-time epochs running through the response. Using this technique, the response is shown to consist of narrow- and frequency peaks or ‘formants’ emerging at different times after stimulus onset. These formants occur at frequencies other than those of the spontaneous EEG and undergo changes in frequency and amplitude over the time course of the response.Two spectrum analysis techniques were employed: the Discrete Fourier Transform and Linear Predictive Coding. Frequency components were successfully identified in single-trial responses using the LPC technique.     

The dynamic and regional characteristics of the high-resolution EEG structure in voluntary activity]

For revealing the dynamics of interrelations between EEG components having stable tuning to individually determined frequencies a dynamical high resolution EEG structure analysis was used. There were three successive experimental stages: rest, motor reproduction of time interval and tapping. Significant increase of EEG components intercorrelations for the right frontal area, minimal number of significant relationships between EEG and movement temporal characteristics, and the occurrence of hemispheric asymmetry in the number of EEG-movement correlations were observed for time reproduction task. This task specifics and the possibilities of used approach for precise functional states differentiation are discussed.