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B Rakerd

Publications and source records attributed to B Rakerd.

12 recordsLinked to original sources
PubMed1992

The I' potential of the brain-stem auditory-evoked potential.

We have consistently recorded a positive wave which precedes wave I, and is called I', within the human brain-stem auditory-evoked potential. It is postulated that I' represents initial neural activity of the auditory nerve, which presumably has as its origin auditory nerve dendrites. Thus, I' may represent a summed far-field dendritic potential from currents of excitatory postsynaptic potentials. We report latency and amplitude values of I'.

Acoustic Stimulation↗
PubMed1992

Structural alterations of an ambiguous musical figure: the scale illusion revisited.

The scale illusion (Deutsch, 1975) shows the importance of frequency range in the perceptual organization of a sequence of notes. This paper includes three experiments on the scale illusion. Experiments 1 and 2 demonstrated that if the structure of the pattern of notes used in the original scale illusion study is altered slightly, by adding or subtracting a pair of notes from the ends of the sequence, there is a significant decrease in the rate of frequency-based responses, suggesting a weaker illusion. Experiment 3 investigated two features of the note patterns that may have led to this change. Specifically, it asked whether the decrease in the strength of the illusion is due to (1) the nature of the notes at the extremes of the frequency range and/or (2) the nature of the notes at the crossing point of the two scales. While both sources were found to affect the strength of the scale illusion, the former had a greater influence.

Adult↗
PubMed1989

Localization of sound in rooms. IV: The Franssen effect.

The Franssen effect is an illusion that causes human listeners to make large errors in localizing a sound source. This paper describes steps taken to convert the illusion into an experiment in order to study the localization precedence effect as it operates in rooms. The results of the experiment suggest that there are two components to the illusion: The first is the inability of listeners to localize a sine tone in a room in the absence of an onset; the second is the obscuring of modulation cues by the irregular transient response of a room. Experiments show that the Franssen effect fails completely in an anechoic environment, as expected if the effect depends upon the implausibility of steady-state cues in a room. The Franssen effect also fails when the spectrum of the sound is dense.

Auditory Perception↗
PubMed1989

A microcomputer-based system for auditory evoked potentials.

We have been using a microprocessor/microcomputer-based system which affords flexibility in the recording of neuroaudiologic and neurophysiologic data. To date, we have used it to record auditory sensory and neural events. Data such as spontaneous oto-acoustic emissions, evoked oto-acoustic emissions, compound action potentials, and auditory brain-stem responses can be recorded, displayed and analysed. The system hardware is configured from commercially available and 'off-the-shelf' components. The software which directs stimulus generation, data recording, data display and analysis is all written in compiled BASIC or C. A hard-disk organizational scheme has also been developed to permit ease in categorizing, storing, and using in-house or commercially available systems, utility and applications software.

Computer Systems↗
PubMed1988

Retention of masculine sexual behavior following castration in male B6D2F1 mice.

The reduction of masculine sexual behavior following castration varies widely among genotypes. In contrast to the loss of sexual behavior by castrated males of other strains, males of the B6D2F1 genotype retain the ejaculatory reflex for many weeks after castration. The present study examined this retention phenomenon. Masculine sexual behaviors were measured before and after castration or sham operation in male C57BL/6J, DBA/2J, and B6D2F1 mice. Castrated C57BL/6J and DBA/2J males showed a rapid decline in copulatory behavior. In contrast, 30% of the B6D2F1 males continued to ejaculate 25 weeks after castration. Regardless of whether or not sexual behaviors were retained, levels of plasma testosterone and hypothalamic nuclear estrogen receptors were reduced by castration. These results suggest that the intra- and inter-strain differences in the retention of sexual behavior following castration are not due to differences in levels of steroid hormones. Further, some B6D2F1 males retain the ability to copulate in the absence of gonadal hormone levels required for the maintenance of sexual behavior in other genotypes.

Animals↗
PubMed1987

Domain-final lengthening and foot-level shortening in spoken English.

The literature describes two kinds of durational influence on the syllables of an utterance. They are a lengthening of syllables before many syntactic boundaries ('domain-final lengthening') and a shortening of stressed syllables followed by unstressed syllables ('foot-level shortening'). In the present study we examined the relationship between these two timing phenomena. In particular, we examined the possibility that syntactic boundaries at which lengthening occurs delimit the domains over which foot-level shortening is realized. To test this hypothesis, we varied the syllabic structure of metrical feet spanning word boundaries that either coincided with a noun-phrase (NP)/verb-phrase (VP) boundary or did not. Comparison of stressed syllable durations in these conditions failed to confirm the hypothesis. Instead, unstressed syllables shortened stressed syllables by the same duration across an NP/VP boundary as within a phrase. Our findings suggest that the two effects are independent. The finding that foot-level shortening spans finally-lengthened syntactic boundaries is discussed in relation to theories of the shortening effect.

Humans↗
PubMed1986

Localization of sound in rooms, III: Onset and duration effects.

The steady-state sound field of a sine tone does not provide useful localization information in a room. Nevertheless, listeners can localize a sine tone in a room if it has an onset transient which allows the precedence effect to operate. In the present study, we made a quantitative assessment of onsets and the precedence effect by systematically varying onset duration from 0 s (impulsive), where the precedence effect is maximal, to 5 s, where there is no precedence effect at all. We also assessed listeners' sensitivity to the steady-state sound field under impulsive conditions by varying the total duration of tone pulses. Our experiments were conducted in a room with a single acoustical reflection having various directions and delays, and in an anechoic room. The results for tones of various frequencies (500 and 2000 Hz) and sound-pressure levels (65 and 40 dBA) indicate the following: Localization in rooms is facilitated by onsets even if the onsets are as long as 100 ms. The facilitation depends upon the peak intensity of the tone, as well as the onset duration, suggesting that onset rate is critical for the precedence effect; our results are most consistent with rate expressed as an increase in sound pressure per unit time. The facilitation also depends upon the reflection delay time for a room; gradual onsets take on much more importance for the precedence effect in rooms with long delays. As onsets begin to lose their effectiveness listeners become increasingly "misdirected" by invalid cues in the steady-state sound field. The pattern of misdirection suggests a perceptual averaging of cues over an interval more than an order of magnitude longer than previous estimates of the summation window for the precedence effect. The pattern of misdirection varies with the frequency of a tone, due to frequency-dependent interference effects in a room, but it is independent of signal level. Localization of an impulsive sine tone in rooms is very insensitive to the pulse duration; this suggests that binaural inhibition models of the precedence effect must be supplemented by an evaluative component that we term the "plausibility hypothesis."

Acoustic Stimulation↗
PubMed1985

A microcomputer-based system for recording and analyzing behavioral data regarding the sexual activity of male rodents.

A microcomputer (TRS-80 Model 4P) based system has been developed to aid in the collection and analysis of behavioral data regarding sexual activity in male rodents. Its capabilities include the recording of events, the online calculation of frequency and latency measures, the monitoring of temporal intervals as demanded by experimental protocols, and the prompting of experimenter activities at prescribed times.

Animals↗
PubMed1985

Linguistic and acoustic correlates of the perceptual structure found in an individual differences scaling study of vowels.

Subjects judged the similarities among a set of American English vowels (See Text) presented in isolation or in a/dVd/ consonantal frame. Individual differences scaling was employed to analyze these similarities data for each of the conditions separately and for the two conditions combined. In all cases, perceptual dimensions corresponding to the advancement, height, and tenseness vowel features were recovered. Given the determinacy of individual differences scaling, this finding is taken to provide strong evidence for the perceptual significance of those features. The perceptual dimensions are considered in relation to various acoustic parameters of the stimuli employed in this study. They are also considered in relation to perceptual dimensions that have been observed in other vowel scaling studies.

Humans↗
PubMed1985

Localization of sound in rooms, II: The effects of a single reflecting surface.

Auditory localization was studied in a room bounded by a single acoustically reflective surface. The position of that surface was varied so as to stimulate a floor, a ceiling, and left and right side walls. The surface was eliminated in one condition so that we could examine localization in free field for purposes of comparison. Using a source identification method we assessed the influences of these various room configurations on the localization of both slow-onset and impulsive sine tones of low frequency (500 Hz). We also measured the steady-state interaural-time-difference (ITD) and interaural-intensity-difference (IID) cues available to subjects in the different room configurations and compared these data with the perceptual judgments. Our results indicate the following: (1) A sound must include transients if the precedence effect is to operate as an aid to its localization in rooms. (2) Even if transients are present the precedence effect does not eliminate all influences of room reflections. (3) Due to the interference of reflections large interaural intensity differences may occur in a room and these have a considerable influence on localization; this is true even at low frequencies for which IID cues do not exist in a free field. (4) Listeners appear to have certain expectations about the reliability and plausibility of various directional cues and perceptually weight the cues accordingly; we suggest that this may explain, in part, the large variation in time-intensity trading ratios reported in the literature and also the differing reports regarding the importance of onsets for localization. (5) In this study we find that onset cues are of some importance to localization even in free field.

Acoustic Stimulation↗