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S D Dalebout

Publications and source records attributed to S D Dalebout.

8 recordsLinked to original sources
PubMed2001

Reliability of the mismatch negativity in the responses of individual listeners.

The mismatch negativity (MMN) was recorded from 12 normal adults during four biweekly sessions. Responses were elicited by a synthetically generated speech contrast (/dalpha/-/galpha/) that all listeners discriminated with at least 90 percent accuracy. Standard and deviant waveforms were replicable across sessions for all listeners; however, replicability of the derived difference waveforms was poor. Of greater importance, the MMN identification rate was too low (29%) to allow reliability to be evaluated. The implications that these findings may have on clinical applicability are discussed.

Adult↗
PubMed2000

Identification of the mismatch negativity in the responses of individual listeners.

The mismatch negativity (MMN) was recorded from normal adults in three stimulus conditions: two contrast conditions and a control condition in which standard and deviant stimuli were identical. Averaged waveforms were analyzed by examiners blind to the evoking stimulus condition. Hit rates, a false alarm rate, and d' values were determined based on the number of MMNs identified in each condition. Hit rates were low and the false alarm rate was relatively high, resulting in unacceptably small d' values. The relationship between MMN findings and corresponding behavioral discrimination data for individual listeners was not systematic. Factors that may contribute to ambiguity and error in MMN data analysis are discussed.

Adult↗
PubMed1998

A tutorial on conducting meta-analyses of clinical outcome research.

Throughout the educational, medical, psychological, and social sciences, meta-analysis is the present-day, broadly accepted means for combining many quasi-experiments in a synthesis for the purpose of establishing the weight of scientific evidence bearing on a certain research question. Meta-analysis thereby is the preferred method for determining the preponderance of evidence in clinical-outcome research relating to questions of treatment efficacy and treatment effectiveness. Relatively few meta-analyses appear in the literature of the communication disorder sciences. The purpose of this tutorial is to enhance the familiarity and accessibility of this technology in the domains of audiology and speech-language pathology. The results of the accompanying example constitute a preliminary meta-analysis of patient-perceived treatment effectiveness. The substance of the tutorial, however, transcends disciplinary interests regarding types of communication disorder.

Communication Disorders↗
PubMed1997

Comparison of the intersubject and intrasubject variability of exogenous and endogenous auditory evoked potentials.

The variability, both between subjects (intersubject variability) and within subjects (intrasubject variability), of the P300 event-related potential was compared to that of early and middle latency components using coefficients of variation. For each of five waveform components, 12 amplitude measures (two trials on each of six measurement occasions) and 12 latency measures were obtained for each of eight subjects. P300 intersubject variability was comparable to that of the most stable early components (ABR waves III and V), both in terms of amplitude and latency. Intrasubject variability was considerably greater for P300 than for the early components; even so, multiple waveforms collected from the same subject tended to fit within an envelope bounded by +/- 1 standard deviation form the mean (averaged) response to oddball stimuli. The variability of MLR component Pa exceeded that of all other components.

Evoked Potentials, Auditory↗
PubMed1991

Determining latency and amplitude for multiple peaked P300 waveforms.

The P300 is characterized by a large positive peak occurring approximately 300 msec post stimulus onset. When a single peak is present, the P300 latency is easily identifiable. However, in cases where the P300 waveform is broadly or multiply peaked, ambiguity exists when attempting to determine the latency of the waveform. Amplitude, while less ambiguous, has also been variously measured as baseline to peak, or peak-to-peak, using either N200 or N300 as the trough. The present study was undertaken to evaluate a method for precisely and consistently determining the latency and amplitude characteristics of the P300 waveform. Three independent raters examined 40 records to determine P300 latency and amplitude according to prescribed criteria. Results indicated that the suggested techniques yield good inter-rater agreement on the latency and amplitude characteristics of the P300 waveform regardless of P300 morphology.

Adult↗
PubMed1991

Effect of speech distinctions and age differences on auditory event-related potentials.

P3 event-related potentials were recorded from 37 subjects in two age groups (19-25 and 61-75 years) listening to tones, stop + vowel (CV) monosyllables, and isolated vowels. P3 latencies were found to be significantly longer for older subjects in all stimulus conditions. CV latencies were also significantly longer than simple tone latencies with the increase being approximately 1.30 msec/year. Latencies to the vowel stimuli were somewhat more variable but also tended to be greater than the tone latencies. P3 amplitudes were greater for the tone stimuli than for the speech stimuli, but no significant age effects were found.

Acoustic Stimulation↗
PubMedDate not supplied

Mismatch negativity to acoustic differences not differentiated behaviorally.

Mismatch negativity (MMN) reportedly reflects the neurophysiologic detection of acoustic differences, rather than the phonemic categorization of speech sounds. The purpose of the present study was to determine if it is elicited by speech contrasts that are acoustically different but are not differentiated by listeners in behavioral tasks. Experimental stimuli were drawn from a synthetically generated continuum that varied in place of articulation from /da/ to /ga/. Contrasts used to elicit MMN were (a) the continuum endpoints, (b) the two-step contrast that straddled each listener's categorical boundary, and (c) a within-category contrast that was not behaviorally differentiated by any of the listeners. MMN responses were elicited by all three experimental contrasts. It appears that MMN may be an index of the neurophysiology underlying the ability or inability to discriminate the acoustic parameters necessary for speech perception, rather than a neurophysiologic correlate of behavioral speech discrimination ability. However, limitations involving identification of MMN in the responses of individual listeners confounded this interpretation.

Adult↗