Waveform moment analysis: An ASYST program for topographical analyses of nonnegative bounded waveforms

The moments of a nonnegative bounded waveform (e.g., bounded probability density functions or responses that can be expressed as bounded probability density functions) provide the basis for characterizing the waveform. Traditionally, only the lower-order moments (k ≤ 4) have been utilized in deriving topographical indices of these waveforms. Recent advances in waveform moment analysis, however, have made it possible to derive comprehensive and interpretable indices of complex nonnegative bounded waveforms by utilizing both lower-order and higher-order moments. Waveform moment analysis is reviewed briefly, and a flexible and efficient computer program is presented for conducting waveform moment analyses.     

Pitch strength and Stevens’s power law

Recent studies have suggested that the saliency or the strength of pitch of complex sounds can be accounted for on the basis of the temporal properties in the stimulus waveform as measured by the height of the first peak in the waveform autocorrelation function. We used a scaling procedure to measure the pitch strength from 15 listeners for four different pitches of complex sounds in which the height of the first peak in the autocorrelation function systematically varied. Pitch strength judgments were evaluated in terms of a modification of Stevens’s power law in which temporal information was used from both the waveform fine structure and the envelope. Best fits of this modified power law to the judged pitch strengths indicate that the exponent in Stevens’s power law is greater than 1. The results suggest that pitch strength is primarily determined by the waveform fine structure, but the stimulus envelope can also contribute to the pitch strength.     

Pitch strength and Stevens's power law

Recent studies have suggested that the saliency or the strength of pitch of complex sounds can be accounted for on the basis of the temporal properties in the stimulus waveform as measured by the height of the first peak in the waveform autocorrelation function. We used a scaling procedure to measure the pitch strength from 15 listeners for four different pitches of complex sounds in which the height of the first peak in the autocorrelation function systematically varied. Pitch strength judgments were evaluated in terms of a modification of Stevens's power law in which temporal information was used from both the waveform fine structure and the envelope. Best fits of this modified power law to the judged pitch strengths indicate that the exponent in Stevens's power law is greater than 1. The results suggest that pitch strength is primarily determined by the waveform fine structure, but the stimulus envelope can also contribute to the pitch strength.     

Correlations,contrasts, and components: Fourier analysis in a more familiar terminology

The Fourier transform partitions the energy in a waveform into the sum of the energies of simpler components. This process is the same as the partitioning of variance into linear contrasts and is a way of measuring the correlation between the waveform and each member of a family of prototype model waveforms. Such a partitioning will often, but not always, result in a meaningful decomposition of the original waveform.     

The Neurotherapy of Anxiety Disorders

Only five studies of patients met criteria for this review. Four of the five had a good clinical outcome. The only one without efficacy reported no enhancement of the target waveform. Of the other four, two reported some enhancement, whereas two gave no details about changes in the target waveform. There were 10 studies of nonpatients with generalized anxiety, of which eight had a good outcome. The decrease of anxiety in these eight studies was correlated with enhancement of the target waveform in five. Three of the eight had no increase of alpha, showing placebo plays a part in neurotherapy. There were nine studies of nonpatients with phobic anxiety, of which six had enhancement of the target waveform accompanied by good outcome. The remaining three studies had poor outcome in spite of enhancement of the target waveform.     

Maturation of the long-latency auditory ERP: step function changes at start and end of adolescence

The auditory event-related potential (ERP) is obtained by averaging electrical impulses recorded from the scalp in response to repeated stimuli. Previous work has shown large differences between children, adolescents and adults in the late auditory ERP, raising the possibility that analysis of waveform shape might be useful as an index of brain maturity. We reanalysed auditory ERPs from samples previously described by Albrecht, von Suchodoletz and Uwer (2000) and Uwer, Albrecht and von Suchodoletz (2002), using the intraclass correlation (ICC) as a global measure of similarity of an individual's waveform to a grand average comparison waveform for each age band. Three developmental periods were clearly distinguished: 5 to 12 years, 13 to 16 years, and adulthood. However, within each of these periods, there was no evidence of any developmental progression with age.     

Minimal conditions for the perception of rotary motion

Abstract.— The necessity of simultaneous length and direction changes for the perception of rotary motion in depth was studied using patterns of one to four segments of a horizontal line. The patterns changed in length only, according to one of four waveforms: A sinusoidal waveform, with both the left and right half of the pattern changing at the same rate (simulating a parallel projection of rotary motion); a sinusoidal waveform, with asymmetric left-right changes (simulating a polar projection of rotary motion); a linear waveform, the same for both the left and right halves (a simple expansion and contraction); and a linear waveform on which the asymmetries of a polar projection were superimposed. Most reports described rotary motion in depth. Both the linearity and the right-left symmetry of the waveforms affected the proportion of rotary motion responses, with the proportions greater for the sinusoidal waveforms and for the asymmetrical waveforms.     

Parallel Factor Analysis of gait waveform data: A multimode extension of Principal Component Analysis

Gait data are typically collected in multivariate form, so some multivariate analysis is often used to understand interrelationships between observed data. Principal Component Analysis (PCA), a data reduction technique for correlated multivariate data, has been widely applied by gait analysts to investigate patterns of association in gait waveform data (e.g., interrelationships between joint angle waveforms from different subjects and/or joints). Despite its widespread use in gait analysis, PCA is for two-mode data, whereas gait data are often collected in higher-mode form. In this paper, we present the benefits of analyzing gait data via Parallel Factor Analysis (Parafac), which is a component analysis model designed for three- or higher-mode data. Using three-mode joint angle waveform data (subjects×time×joints), we demonstrate Parafac's ability to (a) determine interpretable components revealing the primary interrelationships between lower-limb joints in healthy gait and (b) identify interpretable components revealing the fundamental differences between normal and perturbed subjects' gait patterns across multiple joints. Our results offer evidence of the complex interconnections that exist between lower-limb joints and limb segments in both normal and abnormal gaits, confirming the need for the simultaneous analysis of multi-joint gait waveform data (especially when studying perturbed gait patterns).     

The effects of temporal waveform upon temporal darkness enhancement

Temporal darkness enhancement refers to the finding that decremental flashes of 50–140 msec appear darker than longer flash decrements. The present experiment determined the effects of temporal waveform upon darkness enhancement by obtaining darkness judgments for flashes that had abrupt onset/abrupt offset, abrupt onset/gradual offset, gradual onset/abrupt offset, and gradual onset/gradual offset. Temporal darkness enhancement was found only for flashes that had abrupt onsets regardless of offset waveform. These results are discussed in terms of the role of transients in the coding of perceived darkness.     

EMG waveform duration: A validation method for the surface electromyogram

The electromyogram (EMG) recorded with surface electrodes was examined using a triggered oscilloscope technique. When all but the high-amplitude waveforms in a given segment of activity were excluded from analysis, it was found that the duration of the remaining waveforms was specific to the muscle that produced them. That is, waveforms of a given duration were recorded whenever conventional indices-observable contraction, joint movement. needle recordings-showed activity in a specific muscle. This led to the suggestion that waveform duration might be used to validate the surface EMG. The suggestion. which is limited by the need to control posture and electrode placement, both of which may influence waveform duration, was illustrated in application to psychological research.     

Online feedback and the regulation of degrees of freedom in motor control

We tested the hypothesis that the degree to which online feedback is used to control movement influences the regulation of degrees of freedom in a task. Ten participants performed an isometric force production task with their two index fingers with the goal of matching the total force to a target waveform. The role of online feedback was manipulated by changing three factors - the tracking mode, the profile of the target waveform, and the visual gain. The results showed that the coupling between the finger forces was lower in conditions where participants used online feedback to correct their movements compared to conditions where more feedforward strategies were used. The availability of online feedback is dependent on the nature of the task and this contributes to task-dependent changes in the regulation of the degrees of freedom.     

A cricket-song simulator using the 68705 single-chip microcomputer

A cricket-song simulator is described. The device uses a waveform generator to produce a song carrier frequency that is modulated by the 68705 microcomputer. Sixteen different songs can be stored in memory.     

Atypical long-latency auditory event-related potentials in a subset of children with specific language impairment

It has been proposed that specific language impairment (SLI) is the consequence of low-level abnormalities in auditory perception. However, studies of long-latency auditory ERPs in children with SLI have generated inconsistent findings. A possible reason for this inconsistency is the heterogeneity of SLI. The intraclass correlation (ICC) has been proposed as a useful statistic for evaluating heterogeneity because it allows one to compare an individual's auditory ERP with the grand average waveform from a typically developing reference group. We used this method to reanalyse auditory ERPs from a sample previously described by Uwer, Albrecht and von Suchodoletz (2002). In a subset of children with receptive SLI, there was less correspondence (i.e. lower ICC) with the normative waveform (based on the control grand average) than for typically developing children. This poorer correspondence was seen in responses to both tone and speech stimuli for the period 100-228 ms post stimulus onset. The effect was lateralized and seen at right- but not left-sided electrodes.     

ERP evidence of early cross-modal links between auditory selective attention and visuo-spatial memory

Previous dual-task research pairing complex visual tasks involving non-spatial cognitive processes during dichotic listening have shown effects on the late component (Ndl) of the negative difference selective attention waveform but no effects on the early (Nde) response suggesting that the Ndl, but not the Nde, is affected by non-spatial processing in a dual-task. Thus to further explore the nature of this dissociation and whether the Nd waveform is affected by spatial processing; fourteen adult participants performed auditory dichotic listening in conjunction with visuo-spatial memory in a cross-modal dual-task paradigm. The results showed that the visuo-spatial memory task decreased both the Nde and Ndl waveforms, and also attenuated P300 and increased its latency. This pattern of results suggests that: (1) the Nde reflects a memory trace that is shared with vision when the information is spatial in nature, and (2) P300 latency appears to be influenced by the discriminability of stimuli underlying the Nde and Ndl memory trace.     

A pseudorandom noise generator for use in auditory research

A noise generator that is capable of delivering long-duration samples of reproducible noise is described. The noise is generated as a pseudorandom telegraph waveform but may be filtered so that its amplitude distribution is approximately Gaussian. The design and construction of the generator are detailed and a few possible applications are given.     

Octave generalization and the identification of distorted melodies

Four familiar melodies were distorted in such a way that certain harmonic information was maintained. These melodies and their nondistorted versions were randomly presented to three groups of musically untrained subjects. There were, thus, undistorted melodies which were equal in all ways except the frequencies of the constituent tones, three conditions in which only the octave was maintained, and three other harmonic control conditions in which only the perfect fifth, fourth, and major third were maintained. The melodic sequences were presented to each group using a different tonal waveform for each group: sine wave, rectangular wave, and sawtooth wave. An analysis of variance revealed that the octave distortions were significantly more recognizable than the control conditions. Furthermore, waveform significantly influenced identification of melodies. It was proposed that octave generalization was a major factor in the identification of the distorted octave sequences.     

User perceptions and evaluations of short vibrotactile feedback

The objective of the present study was to provide a better understanding of the factors that influence discrimination and subjective assessment of vibrotactile feedbacks during active interaction with a touchscreen. Twenty-four participants were presented with 162 pairs of vibrotactile signals that varied in frequency (60 Hz, 130 Hz, 200 Hz), waveform (sine, square and triangle), and duration (around 123 ms for short and 163 ms for long). Participants had to complete three successive tasks: a dissimilarity task, a preference judgement task, and a resemblance (to push-buttons) judgement task. For the discrimination task, a MultiDimensional Scale analysis revealed: (1) a predominant role of frequency, (2) a role of duration for a given frequency, and (3) no role of waveform. An analysis of variance performed on the preference and resemblance data also point out the main role of the signal frequency. Finally, a correlation was found between preference and resemblance data, indicating that the participants tend to prefer signals judged to be similar to familiar tactile sensations.     

A multidimensional scaling analysis of 16 complex sounds

The INDSCAL multidimensional scaling model was used to investigate the distinctive features involved in the perception of 16 complex nonspeech sounds. The signals differed along four physical dimensions: fundamental frequency, waveform, formant frequency, and number of formants. Scaling results indicated that subjects’ similarity ratings could be accounted for by three psychological or perceptual dimensions. A statistically reliable correspondence was observed between these perceptual dimensions and the physical characteristics of fundamental frequency, waveform, and a combination of the two formant parameters. These results were further explored with Johnson’s (1967) hierarchical clustering analysis. Large differences in featural saliency occurred in the group data with fundamental accounting for more variability than the remaining dimensions. Further analysis of individual subject data revealed large individual differences in featural saliency. These differences were related to past musical experience of the subject and to earlier findings using similar signals. It was concluded that (1) the INDSCAL model provides a useful method for the analysis of auditory perception in the nonspeech mode, and (2) featural saliency in such sounds is likely to be determined by an unspecified attentional mechanism.