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D S Emmerich

Publications and source records attributed to D S Emmerich.

18 recordsLinked to original sources
PubMed1999

Synthetic stimuli attenuate the effect of attention on the dichotic right-ear advantage.

This study assessed attentional effects on the right-ear advantage (REA) for a dichoticlistening task that used synthetic-speech syllables. Presenting subjects with monaural tone cues at various intervals prior to dichotic pairs of natural-speech syllables, T. A. Mondor and M. P. Bryden 1991 (The influence of attention on the dichotic REA. Neuropsychologia, 29, 1179-1190) found a reduced REA with longer intervals. This suggested that tone cues at longer intervals helped overcome a right-ear attentional bias. Despite sufficient statistical power, in the present study no reduction in the REA was found with longer intervals between tones and synthetic-speech syllables. As synthetic-speech stimuli tend to fuse better into the percept of a single stimulus than do natural-speech stimuli, attentional effects on the REA may be reduced with dichotic stimuli that fuse.

Adult↗
PubMed1997

Response bias affects perceptual asymmetry scores and performance measures on a dichotic listening task.

A dichotic listening paradigm discussed by Sidtis and Bryden (Neuropsychologia, 1978, 16, 627-632) allows one to present non-verbal as well as verbal material. This paradigm also permits signal-detection analyses to separate response biases from discrimination abilities. The present study used Sidtis' (Neuropsychologia, 1981, 19, 103-112) Complex Tone Task as an example of the paradigm. Employing signal-detection analyses, we demonstrated that commonly used performance and asymmetry indices are confounded by response bias. Several indices based on signal-detection measures are suggested to replace current widely used measures. As pointed out by Bryden and Sprott (Neuropsychologia, 1981, 19, 571-581), currently the usefulness of a perceptual asymmetry score is mainly determined by mathematical and statistical properties rather than by a theoretical framework. Thus, the choice of a particular index based on signal-detection theory is arbitrary. The present results and those of Katsuki et al. (Journal of Speech and Hearing Research, 1984, 27, 444-448) suggest that the confounding effect of response bias may be present in a variety of experiments investigating lateral processing.

Adolescent↗
PubMed1993

Response latency, latency-based receiver-operating characteristics, and uncertainty about interaural phase in the detection of in-phase and out-of-phase tones presented in noise.

Subjects were given the task of detecting tonal signals presented in a continuous background of white noise which was always in phase at the ears (No). The signals were either in phase (So), or phase-reversed (S pi) at the ears. The analysis of response latencies (for similar levels of performance) indicated that there were consistent differences in the processing of the two types of signals. Latencies were longer, and somewhat more variable, for S pi than for So signals. It was also found that the theory of signal detectability can contribute to an understanding of what and how decisions are made. Latencies were treated as confidence ratings in order to determine latency-based receiver operating characteristics (LROCs) for the detection task. It was observed that the LROCs for the interaural condition No-So tend to leave the origin at a steeper angle than do those for the interaural condition No-S pi, presumably reflecting the different sensory and decision processes employed in the two conditions. When the two interaural conditions were intermixed within blocks of trials, performance was slightly impaired in comparison to the situation in which the interaural condition remained constant throughout blocks of trials.

Acoustic Stimulation↗
PubMed1990

Psychophysical measures of central auditory dysfunction in multiple sclerosis: neurophysiological and neuroanatomical correlates.

Central auditory function was assessed in 15 patients with multiple sclerosis (MS) to determine whether the demyelinating lesions resulted in disruption of temporal processing. Auditory evoked potential (AEP) recordings included all three latency regions: Auditory brain stem responses (ABRs), midlatency responses (MLRs), and long-latency responses (LLRs). Two psychophysical tasks thought to involve temporal processing were used: a monaural-processing task (gap-detection) and a binaural-processing task (masking level difference; MLD). Further, AEP abnormalities and psychophysical performance deficits were related to lesion location, based on magnetic resonance imaging (MRI) scans. Reduced MLDs were seen in six MS subjects. Abnormal MLDs were always accompanied by abnormal ABRs and MLRs, and compared to subjects with normal MLDs, the subjects with abnormal MLDs were more likely to have bilateral abnormalities in the AEPs. Further, MLR indices of abnormal binaural interaction appeared to be specifically related to the psychophysical measure of binaural processing. The MRI data of these patients indicated widespread involvement of the auditory pathway. MS subjects with abnormal MRI signals restricted to levels caudal to the lateral lemniscus did not have abnormal MLDs. Gap-detection thresholds were more resistant to the effects of the demyelinating lesions; only two subjects had abnormal gap-detection thresholds. These subjects had extensive AEP abnormalities (bilaterally, in all three latency regions). The gap-detection thresholds were most specifically related to abnormalities of the LLRs. In addition, the subjects with elevated gap-detection thresholds were the only ones with a prolonged interval between the ABRs and MLRs. Thus, efficient neural conduction between the upper brain stem and auditory cortex appears to be crucial for normal monaural temporal processing. The results indicate that demyelinating lesions can cause deficits in temporal processing in the central auditory pathway. However, auditory temporal processing is not a unitary phenomenon since abnormalities at different levels of the auditory system disrupt different types of temporal processing. Finally, abnormal psychophysical performance was not seen in all subjects with AEP and MRI evidence of involvement of the auditory pathway; rather, these psychophysical measures appeared to be sensitive to disruption only in specific portions of the auditory system.

Adolescent↗
PubMed1990

Monaural envelope correlation perception, revisited: effects of bandwidth, frequency separation, duration, and relative level of the noise bands.

This article presents the results of two experiments investigating performance on a monaural envelope correlation discrimination task. Subjects were asked to discriminate pairs of noise bands that had identical envelopes (referred to as correlated stimuli) from pairs of noise bands that had envelopes which were independent (uncorrelated stimuli). In the first experiment, a number of stimulus parameters were varied: the center frequency of the lower frequency noise band in a pair, f1; the frequency separation between component noise bands; the duration of the stimuli; and the bandwidth of the component noise bands. For a long stimulus duration (500 ms) and a relatively wide bandwidth (100 Hz), subjects could easily discriminate correlated from uncorrelated stimuli for a wide range of frequency separations between the component noise bands. This was true both when f1 was 350 Hz, and when f1 was 2500 Hz. In each case, narrowing the bandwidth to 25 Hz, or shortening the duration to 100 ms, or both, made the task more difficult, but not impossible. In the second experiment, the level of the higher frequency noise band in a pair was varied. Performance did not decrease monotonically as the level of this band was decreased below the level of the other band, and only showed marked impairment when the level of the higher frequency band was at least 60 dB below that of the lower frequency band. The pattern of results in these two experiments is different from that which is obtained when the same stimulus parameters are varied in experiments investigating comodulation masking release (CMR). This suggests that the mechanisms underlying CMR and those underlying the discrimination of envelope correlation are not identical.

Acoustic Stimulation↗
PubMed1989

Differences in the responses of heterozygous carriers of colorblindness and normal controls to briefly presented stimuli.

Two experiments were conducted in order to investigate the possible effects of X-inactivation (Lyon, 1961) on female carriers of colorblindness. The results of the first experiment, like those of Grützner et al. (1976), were consistent with the prediction of the Lyon (1961) hypothesis that the retinas of female carriers are composed of mosaic patches of colorblind and normal areas. In this first experiment, rows and columns of colored spots were presented tachistoscopically, and subjects were asked to identify the colors of the spots. In the second experiment, plates from the Ishihara test of colorblindness were presented tachistoscopically and subjects were asked to identify the number which was embedded in the pattern of colored dots. Both experiments support the Lyon hypothesis in that female carriers were found to have more difficulty in perceiving patterns of colored stimuli than did control subjects, and they suggest that the amount of time that a carrier has to scan colored stimuli plays an important role in her ability to accurately perceive them.

Color Perception↗
PubMed1989

An investigation of the facilitation of simple auditory reaction time by predictable background stimuli.

Two experiments explored a surprising result reported by Emmerich, Pitchford, and Becker (1976): Simple reaction time (RT) to an auditory stimulus can be facilitated by the presence of a tonal background (or masker). In the first experiment, simple RT to a tonal signal was investigated for a variety of background frequencies and loudness levels, and significant facilitation of RT was found for low levels of the background. In the second experiment, no evidence of facilitation was found when the background stimulus was a randomly varying narrow-band noise, although evidence for facilitation was again found with a constant tonal background.

Adult↗
PubMed1988

The relationship between auditory sensitivity and ear asymmetry on a dichotic listening task.

Using an adaptive forced-choice procedure, the average absolute sensitivity of the right ears of a group of right-handed males was found to be slightly greater than that of their left ears. There was no ear difference in performance on a monaural syllable-identification task using easily detectable stimuli, however. The magnitude of the ear difference in absolute sensitivity was significantly correlated with performance on a dichotic-listening task. In a second experiment, the adaptive forced-choice procedure was used to assess differences in absolute sensitivity in a group of left-handed males. The right ears of those left-handers showing a right-ear advantage on the dichotic-listening task were slightly more sensitive than their left ears. The left ears of those left-handers showing a dichotic left-ear advantage were slightly, but not significantly, more sensitive than their right ears. The correlation of the ear differences in absolute sensitivity with performance on the dichotic-listening task for the left-handers was not significantly different from zero. Results of both experiments are discussed in terms of their implications for the nature of hemispheric asymmetry of function, and the interpretation of dichotic and monaural asymmetries.

Adult↗
PubMed1987

Edge effects on frequency discrimination of tones presented in low- and high-pass noise backgrounds.

Previous research has indicated that frequency discrimination performance is poorer for tones presented near the sharp spectral edge of a low-pass noise than for tones presented near the edge of a high-pass noise, or for tones in the same low-pass noise with high-pass noise added [Emmerich et al., J. Acoust. Soc. Am. 80, 1668-1672 (1986)]. The present study extends these findings in order to investigate how the steepness of the spectral edges of low- and high-pass maskers influences the discriminability of tones presented near these edges. Frequency discrimination was measured in each of three high- and low-pass noise backgrounds (which differed in the steepness of their filter skirts). The following results were obtained: (1) In the low-pass noise background, frequency discrimination performance improved as the filter skirt became more gradual; (2) in the high-pass noise background, performance first improved and then became poorer as the filter skirt became shallower; and (3) performance in low-pass noise was poorer than that in high-pass noise for the two steepest slopes employed (96 and 72 dB/oct) but not for the shallower slope (36 dB/oct). Results are discussed in the context of lateral suppression and edge pitch effects, and of a trade-off between possible edge effects and masking.

Acoustic Stimulation↗
PubMed1986

Frequency discrimination of tones presented in filtered noise.

Previous research (Emmerich et al., 1983) in which tones were presented in the center of the notches in band-reject noise backgrounds suggests that information from frequency regions remote from the nominal signal frequency is useful in frequency discrimination. The present work extends the earlier findings by presenting tones on either side of a notch so that only one (or the other) tail of the excitation patterns of the tones would fall into the notch. In addition, tones were presented in high-pass noise, low-pass noise, and various combinations of the two. The results again indicate that remote information affects frequency discrimination, and they are also consistent with the hypothesis that the low-frequency tail of the excitation pattern is more useful for frequency discrimination than is the high-frequency tail.

Female↗
PubMed1984

Laterality effects in response to the offset of visual stimuli.

In a study of simple reaction time to visual stimuli it was found that the offset (or termination) of stimuli presented in the right visual field elicits significantly later responses than does the offset of stimuli presented in the left visual field. No such difference was observed for the responses to stimulus onset. A similar effect has been reported for responses to tonal stimuli. The results do not support the view that hemispheric asymmetries arise at higher stages of information processing than those which mediate simple reaction time.

Color Perception↗
PubMed1983

Frequency discrimination and signal detection in band-reject noise.

An experiment was conducted in order to compare the importance of information from frequency regions remote from the nominal signal frequencies for frequency discrimination and signal detection. In both tasks, signals were presented within the "notch" of band-reject noise, and different notch widths were employed. The results indicate that information is integrated over a wider range in frequency discrimination than in signal detection. Further, experiments in which a noise floor was present as well as band-reject noise, indicate that disrupting the information from regions remote from the nominal signal frequencies impairs frequency discrimination even in the absence of any significant impairment of signal detection performance.

Auditory Perception↗
PubMed1978

A duration effect in reaction time to the offset of brief auditory stimuli.

A previous study reported no difference in reaction time to the offset of brief bursts of noise as a function of stimulus duration. However, in that study a fixed foreperiod preceded stimulus onset, and the stimulus duration remained constant within blocks of trials. In the present study it was found that when foreperiods and durations are selected randomly from trial to trial, reaction time does vary significantly as a function of stimulus duration.

Acoustic Stimulation↗