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Biomedical subjects

V J Samar

Publications and source records attributed to V J Samar.

At least 19 recordsLinked to original sources
PubMed2000

College teachers' perceptions of English language characteristics that identify English language learning disabled deaf students.

Deaf individuals typically experience English language difficulties at all levels of linguistic knowledge. Hearing individuals with English language learning disabilities (LD) can exhibit the same kinds of English language difficulties as deaf individuals. Although the existence of deaf individuals who also have LD has long been recognized, no definite criteria for identifying them exist, partly because of the confounding effects of deafness and LD on English language development. Despite the confound, previous surveys suggest that teachers believe atypical English-language behavior is a potential diagnostic marker for LD in deaf individuals. In the present study, a survey solicited the intuitions of experienced teachers and tutors of English to deaf college students regarding the degree of difficulty deaf students with and without LD might be expected to have in dealing with 30 specific English language phenomena. Spelling knowledge and a variety of English discourse, lexical syntactic, and morphological phenomena emerged as candidates for further study as potential markers of LD in the deaf population.

Adolescent↗
PubMed1999

Wavelet analysis of neuroelectric waveforms: a conceptual tutorial.

This paper presents a nontechnical, conceptually oriented introduction to wavelet analysis and its application to neuroelectric waveforms such as the EEG and event related potentials (ERP). Wavelet analysis refers to a growing class of signal processing techniques and transforms that use wavelets and wavelet packets to decompose and manipulate time-varying, nonstationary signals. Neuroelectric waveforms fall into this category of signals because they typically have frequency content that varies as a function of time and recording site. Wavelet techniques can optimize the analysis of such signals by providing excellent joint time-frequency resolution. The ability of wavelet analysis to accurately resolve neuroelectric waveforms into specific time and frequency components leads to several analysis applications. Some of these applications are time-varying filtering for denoising single trial ERPs, EEG spike and spindle detection, ERP component separation and measurement, hearing-threshold estimation via auditory brainstem evoked response measurements, isolation of specific EEG and ERP rhythms, scale-specific topographic analysis, and dense-sensor array data compression. The present tutorial describes the basic concepts of wavelet analysis that underlie these and other applications. In addition, the application of a recently developed method of custom designing Meyer wavelets to match the waveshapes of particular neuroelectric waveforms is illustrated. Matched wavelets are physiologically sensible pattern analyzers for EEG and ERP waveforms and their superior performance is illustrated with real data examples.

Brain↗
PubMed1999

Time-frequency analysis of single-sweep event-related potentials by means of fast wavelet transform.

A time-frequency decomposition was applied to the event-related potentials (ERPs) elicited in an auditory oddball condition to assess differences in cognitive information processing. Analysis in the time domain has revealed that cognitive processes are reflected by various ERP components such as N1, P2, N2, P300, and late positive complex. However, the heterogeneous nature of these components has been strongly emphasized due to simultaneously occurring processes. The wavelet transform (WT), which decomposes the signal onto the time-frequency plane, allows the time-dependent and frequency-related information in ERPs to be captured and precisely measured. A four-octave quadratic B-spline wavelet transform was applied to single-sweep ERPs recorded in an auditory oddball paradigm. Frequency components in delta, theta, and alpha ranges reflected specific aspects of cognitive information processing. Furthermore, the temporal position of these components was related to specific cognitive processes.

Adolescent↗
PubMed1998

Round-off error, blind faith, and the powers that be: a caution on numerical error in coefficients for polynomial curves fit to psychophysical data.

Graphing and statistics software often permits users to fit polynomial curves, like a parabola or sigmoid, to scatter plots of psychophysical data points. These programs typically calculate the curve using double- or extended-precision numerical algorithms and display the resulting curve overlaid graphically on the scatter plot, but they may simultaneously display the equation that generates that curve with numerical coefficients that have been rounded off to only a few decimal places. If this equation is used for experimental or clinical applications, the round-off error, especially on coefficients for the higher powers, can produce anomalous findings due to systematic and extreme distortions of the fitted curve, even artifactually reversing the algebraic sign of the true slope of the fitted curve at particular data points. Care must be exercised in setting round-off criteria for coefficients of polynomial terms in curve-fit equations to avoid nonsensical measurement and prediction.

Computer Graphics↗
PubMed1996

Deaf adults' attitudes toward career choices for deaf and hearing people in India.

This study investigated the expressed attitudes of deaf people in India toward career choices for deaf and hearing people. Deaf adults from Pune, India rated the suitability of 12 professions for deaf and hearing people and gave written comments on the suitability of any other professions they could list. The results, in general, were consistent with those of other studies in the United States, England, Italy, South Africa, and India with hearing teachers and parents of deaf children, which indicated that the hearing status of imagined deaf and hearing advisees selectively influenced attitudes toward the suitability of certain professions. Some differences in profession preferences also emerged indicating that the deaf respondents' criteria for career choice appeared to be primarily based on the use of hearing, speech, and visual skills required for a particular career. There was some suggestion that culturally specific factors played a role in shaping attitudes. These findings underscore the importance of understanding the attitudes of deaf people.

Adolescent↗
PubMed1995

Artifactually induced VEP classification of form and color attributes: a refutation of "Neuroelectric concepts: form-color classification" by William J. Hudspeth (1993)

An algebraic analysis of the procedures used in "Neuroelectric Concepts: Form-Color Classification," Brain and Cognition, 21, 226-246 (1993) by William J. Hudspeth reveals that the article's results are artifactual, having been produced by the introduction of strong linear dependencies during data transformation. The same pattern of principal results is shown to obtain by applying Hudspeth's procedures both to arbitrarily selected EP input data having no connection to form or color discrimination, and to waveforms composed of sequences of random numbers.

Artifacts↗
PubMed1995

Multiresolution analysis of event-related potentials by wavelet decomposition.

Wavelet analysis is presented as a new tool for analyzing event-related potentials (ERPs). The wavelet transform expands ERPs into a time-scale representation, which allows the analyst to zoom in on the small scale, fine structure details of an ERP or zoom out to examine the large scale, global waveshape. The time-scale representation is closely related to the more familiar time-frequency representation used in spectrograms of time-varying signals. However, time-scale representations have special properties that make them attractive for many ERP applications. In particular, time-scale representations permit theoretically unlimited time resolution for the detection of short-lived peaks and permit a flexible choice of wavelet basis functions for analyzing different types of ERPs. Generally, time-scale representations offer a formal basis for designing new, specialized filters for various ERP applications. Among recently explored applications of wavelet analysis to ERPs are (a) the precise identification of the time of occurrence of overlapping peaks in the auditory brainstem evoked response; (b) the extraction of single-trial ERPs from background EEG noise; (c) the decomposition of averaged ERP waveforms into orthogonal detail functions that isolate the waveform's experimental behavior in distinct, orthogonal frequency bands; and (d) the use of wavelet transform coefficients to concisely extract important information from ERPs that predicts human signal detection performance. In this tutorial we present an intuitive introduction to wavelets and the wavelet transform, concentrating on the multiresolution approach to wavelet analysis of ERP data. We then illustrate this approach with real data. Finally, we offer some speculations on future applications of wavelet analysis to ERP data.

Brain↗
PubMed1994

A moral justification for gay and lesbian civil rights legislation.

This essay explores, in two parts, the problems of justifying civil rights legislation for gays, lesbians, and bisexuals. Part I shows that discrimination against gays and lesbians at least in respect to employment, housing, and public accommodations is an evil unsupported by ethical traditions in utilitarianism, rights theory, and communitarianism. It also shows that two theories, Kantian theory and natural law theory, which do support such discrimination on the claim that homoerotic behavior is universally or objectively immoral only do so because of a failure to make precise the concept of "natural" which underlies those theories. Part II argues that anti-discrimination legislation is both an appropriate and effective means to promote the idea that discrimination against lesbians and gays in respect to most employment, housing, and public accommodations is sufficiently injurious to both individuals and society that it should not be tolerated. The section also explains how such legislation might succeed practically in eliminating discrimination in these areas.

Bisexuality↗
PubMed1992

Spectral study of deviant resonance in the speech of women who are deaf.

In a previous radiographic study of 4 deaf women, some aberrant features in vocal tract configuration were identified for vowels produced with excessive pharyngeal resonance. These features included neutralization of tongue position, elevation of the hyoid, and a retraction of the tongue, associated with a deflection of the epiglottis in the lower pharynx. The vowels, produced simultaneously with X-ray exposure, were analyzed spectrographically to study acoustic correlates of the vocal tract deformation. Comparisons of the formants for vowels /i/ /u/ and /a/ produced by the deaf women with mean formant values for these vowels produced by normal-hearing women revealed no consistent pattern of second-formant deviation. Formant structure evaluated on isovowel lines disclosed consistent neutralization of vowels, with F2 values clustering in the 1500-2100 Hz frequency range, which is attributed to the observed restricted horizontal movements of the tongue within the oral and pharyngeal cavities. If such restrictions affect the production of all vowels, a lower F2 might be assumed for the front vowels, which normally have a high F2; a higher F2 frequency would be anticipated for back vowels, which normally have a low F2. The limited sample studied supports this assumption.

Adult↗
PubMed1990

Spoken and written English errors of postsecondary students with severe hearing impairment.

This investigation compared the spoken and written English errors of 20 hearing-impaired postsecondary students with intelligible speech and poor English language. Error categories used to assess the language samples were function, content, and structure. Spoken and written performances were distinguished only by a greater number of function word errors in writing samples. A trend toward greater complexity in writing was also found. Implications for instruction are discussed.

Adult↗
PubMed1990

Acoustic dimensions of hearing-impaired speakers' intelligibility: segmental and suprasegmental characteristics.

Regression and principal components analyses were employed to study the relationship between 28 segmental and suprasegmental acoustic parameters of speech production and measures of speech intelligibility for 40 severely to profoundly hearing-impaired persons in an effort to extend the findings of Metz, Samar, Schiavetti, Sitler, and Whitehead (1985). The principal components analysis derived six factors that accounted for 59% of the variance in the original 28 parameters. Consistent with the findings of Metz et al., a subsequent regression analysis using these six factors as predictor variables revealed two factors with strong predictive relationships to speech intelligibility. One factor primarily reflected segmental production processes related to the temporal and spatial differentiation of phonemes, whereas the other primarily reflected suprasegmental production processes associated with contrastive stress. However, the predictive capability of the present factor structure was somewhat reduced relative to the findings of Metz et al. (1985). Data presented indicate that the populations sampled in the two studies may have differed on one or more dimensions of subject characteristics. Considered collectively, the present findings and the findings of Metz et al. support the tractability of employing selected acoustic variables for the estimation of speech intelligibility.

Adult↗
PubMed1989

Articulatory dimensions of hearing-impaired speakers' intelligibility: evidence from a time-related aerodynamic, acoustic, and electroglottographic study.

Regression and principal components analyses were employed to study the relationship between 30 aerodynamic speech parameters and the speech intelligibility of 40 severely to profoundly hearing-impaired speakers. Regression analysis on the original 30 aerodynamic variables revealed that speech intelligibility was predicted by a cognate-pair voice onset-time difference measure and a measure of the stability of the volume-velocity rise time. Principal components analysis of the 30 independent variables derived seven factors that accounted for 84.3% of the variance in the original 30 parameters. Subsequent regression analysis using the seven factors as predictor variables revealed four factors with independent relationships to speech intelligibility. These included a factor that reflected cognate-pair voice onset-time distinctions, a factor that reflected cognate-pair peak volume-velocity distinctions, and two other factors, which reflected production stability of temporal distinctions between cognate pair members.

Adult↗
PubMed1989

A cognitive/experiential approach to aural rehabilitation.

This paper describes an experiential speechreading course that was designed to provide hearing-impaired students with real-life communication experiences. The course, intended to function as a supplement to traditional speechreading courses, was evaluated with a self-evaluation questionnaire completed by students who took the course and by a matched control group. Results indicate that the course was effective in increasing student self-perceptions of communication success in real-life situations.

Attitude↗
PubMed1988

Criterion validity of speech intelligibility rating-scale procedures for the hearing-impaired population.

The criterion validity and reliability of two popular rating-scale procedures for the assessment of the contextual speech intelligibility of hearing-impaired individuals (The NTID Scales) were studied under clinically typical conditions of test administration and evaluation. The criterion measure was a write-down procedure based on subjects' readings of sentence lists chosen from The CID Everyday Sentence lists. Although the results revealed generally high overall validity and reliability coefficients for the two scales, a close examination of the distribution of estimation error over the full range of rating-scale values revealed gross violations of measurement prediction within the clinically most frequent midrange of speech intelligibility. The results indicate that the rating-scale procedure significantly compromises clinical and research classification of an individual's speech intelligibility and that write-down procedures may provide a viable and significantly more accurate alternative for speech intelligibility assessment.

Adult↗
PubMed1986

The syntactic priming effect: evoked response evidence for a prelexical locus.

Twenty subjects made lexical decisions in a syntactic priming paradigm. Target stimuli (nouns, verbs, abiguous noun--verb words, and nonsense words) were immediately preceded on each trial by a function word syntactic prime, creating appropriate or inappropriate syntactic contexts for the real word targets. Evoked responses to the targets were recorded from left and right frontal, temporal, and temporoparietal sites. Principal components analysis revealed a component peaking at 140 msec which discriminated words in appropriate contexts from words in inappropriate contexts, independent of lexical syntactic class, with maximal discrimination at temporoparietal sites. Evidence for the identification of the syntactic class of target items was not observed in the evoked response until 80 msec after this syntactic priming effect occurred. These results suggest a prelexical locus for the syntactic priming effect. The implications of these results for current conceptions of the modularity of the mental lexicon are discussed.

Brain Mapping↗
PubMed1986

Changes in aerodynamic characteristics of stutterers' fluent speech associated with therapy.

Stuttering frequency and four aerodynamic measures of articulatory events within perceptually fluent voiced and voiceless intervocalic intervals were obtained from 15 stutterers prior to and at the termination of a concentrated program of stuttering therapy. Three of the four aerodynamic variables showed group changes over the course of therapy concomitant with improvements in fluency. Additional correlational analyses suggested that one of the aerodynamic variables was specifically related to stuttering frequency. It is argued that both fluency enhancing and ancillary components of therapy operate to influence the intervocalic interval.

Adult↗