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Biomedical subjects

D C Teas

Publications and source records attributed to D C Teas.

At least 19 recordsLinked to original sources
PubMed1990

The effects of acoustic orientation cues on instrument flight performance in a flight simulator.

An initial version of an acoustic orientation instrument (AOI), in which airspeed was displayed as sound frequency, vertical velocity as amplitude modulation rate, and bank angle as right-left lateralization, was evaluated in a T-40 (Link GAT-3) motion-based simulator. In this study, 15 pilots and 3 non-pilots were taught to use the AOI and flew simulated flight profiles under conditions of neither visual nor auditory instrumentation (NO INPUT), AOI signals only (AOI), T-40 simulator instrumentation only (VISUAL), and T-40 simulator instrumentation with AOI signals (BOTH). Bank control under AOI conditions was significantly better than under the NO INPUT condition for all flying tasks. Bank control under VISUAL conditions was significantly better than under the AOI condition only during turning and when performing certain complex secondary tasks. The pilots' ability to use the AOI to control vertical velocity and airspeed was less apparent. However, during straight-and-level flight, turns, and descents the AOI provided the pilots with sufficient information to maintain controlled flight. Factors of potential importance in using sound to convey aircraft attitude and motion information are discussed.

Acoustic Stimulation↗
PubMed1985

Postnatal development of physiological responses in auditory nerve fibers.

The discharges of auditory nerve fibers in kittens 4-37 days of age were recorded from micropipette electrodes. Tuning curves, thresholds, and the degree of tuning (Q 10) are compared over this age range. The tuning curves for fibers during the first postnatal week are relatively flat, with thresholds above 100 dB SPL. The response areas of VIII-nerve fibers during this period are restricted to low-to-middle frequencies. With increasing age there is a reduction in threshold and an increase in the sharpness of tuning which is dependent on fiber CF. Response characteristics similar to adult VIII-nerve fibers were observed first for fibers with CFs near 5 kHz. For the response measures used here, VIII-nerve fibers in kittens are adultlike by the third to fourth postnatal week. The results are discussed in relation to the morphological development of the cochlea reported by other investigators.

Aging↗
PubMed1983

Relation between discharges in auditory nerve fibers and the whole-nerve response shown by forward masking: an empirical model for the AP.

Whole-nerve action potentials evoked by a standard click were recorded from a gross electrode on the RW and the discharges of auditory nerve fibers to the same standard click were recorded from micropipette electrodes in the auditory nerve. The effect of a preceding tone burst (2, 4, or 8 kHz) upon the responses was measured for forward-masker intensities from 20 to 80 dB SPL. All forward maskers reduced the discharges of auditory nerve fibers to the standard click with the greatest reduction occurring for fibers with characteristic frequencies (CFs) near the masker frequency. The 4- and 8-kHz forward maskers produced similar effects on N1, P1, and N2 of the RW response. However, the 2-kHz forward masker produced enhancement at P1 and N2 in the RW response to the standard click. An empirical summation model of estimated elemental waveforms at latencies dependent on CF produces synthesized AP response waveforms which are similar to the observed RW response. The model permits the exclusion of discharges from segments along the cochlear partition in a manner similar to the effect of a forward masker. Alterations in the synthesized waveforms due to the exclusion of segments are similar in direction to the alterations observed in the RW responses for forward masking.

Acoustics↗
PubMed1983

References to contemporary papers on acoustics.

In most of the following references, the author's name is followed by the title of the paper or book in boldface, the journal, the volume number in boldface, the issue number in parentheses, the page reference, and lastly, in parentheses, the year. Where reference is made to abstract journals that number their abstracts, the abstract number is given instead of a page reference. Abstracts in Annales des Tèlècommunications are in French and those for Referativnyi Zhurnal, Fizika (three series, E, I, Zh) are in Russian [where, e.g., Ref. Zh. Fiz. 7 E425 (1979) means: July issue, E, abstract no. 425, year 1979.] When possible, the abbreviations for the names of the journals follow those in Bibliographic Guide for Editors & Authors (1974). A number preceded by the letters AD, DE, PB, or N refers to the accession/report number of the Government Reports Announcements & Index. The numbers to the left of the sections and sub-sections in this volume correspond to those that appear in the Classification of Subjects preceding the index in the June 1983 issue of JASA. Compiled from various sources. For many of the journals referred to here, those interested will find their addresses in either the semi-annual Author Index of Physics Abstracts or the annual Physics Briefs: List of Abstracted Periodical and Serial Publications.

Acoustics↗
PubMed1982

Forward masking of auditory nerve and brainstem responses using high-pass noise maskers.

The effects of varying the low-frequency cutoff of a high-pass noise used as a forward masker for a broadband click (40 dB HL) are compared for wave V of the auditory brainstem response and N1 from the ear canal. Derived responses were also obtained using a waveform subtraction technique. N1 amplitude and wave V latency were most sensitive to the changes in the masker low-frequency cutoff. Results suggest that N1 is biased toward the high frequencies, most likely because of its requirements for high neural synchrony, and is not necessarily related to the maximum area of excitation. Wave V, on the other hand, seems to be less dependent upon highly synchronous events and is more closely related to activity in the mid-to-lower frequencies. Complex behavior of wave V was observed as a function of delta T which suggests that temporal as well as spatial factors can interact in their contributions to wave V.

Acoustic Stimulation↗
PubMed1982

An analysis of auditory brainstem responses in infants.

Acoustic brainstem responses (ABRs) were recorded from 148 infants from 4 to 60 weeks of age. 28 subjects returned to the laboratory 3 or more times for additional recordings. Filtered clicks of 1, 2, 4 and 8 kHz were presented at two intensities, 30 and 50 dB HL re the average threshold for a group of young adults. Responses to a broadband click, 50 dB nHL, were also recorded. The latencies of waves I, III and V were measured. Wave I latencies for the 8 kHz filtered click showed no change but those for lower frequencies decreased with age. The latency decreases with age were largest for wave V, and, among the filtered clicks, was largest for the responses to 1 kHz. Best-fitting curves were determined for latency vs. age for each filtered click and for the broadband click. Wave V--Wave I latency differences showed that the rostral conduction time for responses to the 8 kHz FC decreased with age and, for the 1 kHz filtered click (50 dB), remained constant. The early development of basal regions in the cochlea is viewed as insuring the delivery of a wide range of frequencies to rostral segments of the auditory system. The limiting feature of maturation is at rostral sites. The immature auditory system appears to be fully capable of transducing low frequency stimuli, but not high frequencies.

Acoustic Stimulation↗
PubMed1982

Forward masking of auditory nerve (N1) and brainstem (wave V) responses in humans.

Wave V of the auditory brainstem response and N1 from the ear canal were recorded from normal hearing adults using a forward masking paradigm. Response amplitudes and latencies to 40 dB HL probe clicks presented in quiet and as a function of the time delay (delta T) following short-duration wideband noise maskers were measured. The masking effects for wave V were different than for N1. The primary effects were decreases in N1 amplitude and increases in wave V latency, neither of which were recovered by delta T = 100 ms. The V-N1 latency interval increased for delta Ts below 50 ms. Wave V amplitude was fully recovered by delta T = 25 ms, even though N1 amplitude was significantly reduced. Recovery functions are also described for some variations in masker duration and masker level. Results are explainable in terms of peripheral and central processes or entirely peripheral processes. The differential effects of N1 and wave V suggest, at least for some stimulus conditions, that these two responses are to some degree independent of each other.

Adult↗
PubMed1979

A technique for separating endogenous from exogenous human cortical potentials.

In a temporal discrimination paradigm, if signal duration is the stimulus dimension to be discriminated, the moment of subject's decision can be manipulated by varying the duration of the target stimulus. As stimulus duration is lengthened, task-contingent potentials related to the decision process can be separated from those evoked by stimulus onset. Analysis of individual evoked responses indicates that 3 task-contingent components, occurring at 220, 300 and 340 msec are precisely time-locked to the moment of decision.

Acoustic Stimulation↗
PubMed1979

BSR (wave V) and N1 latencies in response to acoustic stimuli with different bandwidths.

Shortlatency averaged responses to 0.02--6 kHz broadband (BB) and 2 kHz narrow-band (NB) filtered clicks were recorded from the ear canal and the vertex of five adults with normal audiograms. Response latencies to the signals presented in quiet and with masking noise were compared. For constant spectrum level, the low-frequency limit of the masking noise was systematically increased to 6 kHz. The upperfrequency limit was always 8 kHz. For signals at 40 dB HL, the latencies of wave V and N1 decreased as the lower limit of the noise was raised and nearly equaled the latency for the signals presented in quiet. For signals at 70 dB HL, the latency in quiet was much less than that observed for all noise conditions, i.e., frequencies above 8 kHz would be required to interfere with the signal-dependent synchronous neural activity. Similar effects were measured for both wave V and N1, but the analysis of wave V and N1, but the analysis of wave V--N1 latency intervals suggested a possible signal dependency.

Acoustic Stimulation↗
PubMed1978

Acoustically dependent latency shifts of BSER (wave V) in man.

The latencies of wave V in Brain Stem Evoked Responses (BSER) elicited by a set of acoustic transients were measured. The stimuli were produced by delivering pulses to two filters, arranged in series. The filters were set so that the maximum acoustic energy in the transients, i.e., filtered clicks, occurred at 0.5, 1, 2, 4, or 8 kHz. The filtered clicks were presented via earphones at a rate of 30/s at 20, 40, or 60 dB HL to ten subjects with normal hearing. The latencies of wave V varied systematically with center frequency of the filtered clicks when they were each at the same HL. Stimuli presented at 40 dB HL produced the greatest opportunity for relating stimulus frequency to latency. The latencies for a smaller set of responses to stimuli presented at 10/s were the same as those for the principal data taken at 30/s. The changes in latency of wave V due to frequency are similar to those observed by other investigators in whole-nerve responses recorded in man.

Acoustic Stimulation↗
PubMed1977

Electrocochleographic changes in acoustic neuroma: some experimental findings.

Reversible experimental lesions were produced in the central end of the cochlear nerve at the IAM of guinea pigs by various procedures, including the instillation of KCl (0.1 or 0.01 M). As a result the usual diphasic AP waveforms seen in guinea pigs (when click stimuli are used) were transformed into monophasic, widened negative waves. This change, attributed to a neural block, was reversible, e.g. when the instilled KCl was dispersed by irrigation with normal saline. It is suggested that the widened monophasic negative AP's observed at ECochG in cases of acoustic neuroma or similar lesions, are produced in this way.

Action Potentials↗
PubMed1976

Single unit study of binaural interaction in the auditory cortex of the chinchilla.

The primary aim of this investigation was to systematically compare for various stimulus conditions the relative influences of contralateral and ipsilateral acoustic stimulation on cortical single units in an unanesthetized preparation and to study the effects upon single unit responses of the dominant stimulus cues for sound localization--interaural intensity difference (deltaI) and interaural time difference (deltat). Recordings were obtained from 133 units in chinchillas immobilized by gallamine triethiodide. All units were found to be influenced by input from both ears. Unit thresholds for contralateral stimulation were lower and more discharges were elicited than for ipsilateral stimulation over a range of intensities from unit threshold intensity to 80 dB sound-pressure level. A predominance of contralateral influence was also observed when the number of stimulus-evoked discharges was plotted as a function of the deltaI or deltat. For 62% of the deltaI functions maximal responsiveness occurred for binaural stimuli that were more intense at the contralateral ear. Similarly, of the 36 units that showed sensitivity to deltat parameters for tone stimuli, 22 (61%) were maximally responsive at the contralateral-leading deltat intervals. For click stimuli, maximal responsiveness for all 21 deltat-sensitive units also occured for contralateral-leading stimuli. Certain observations in the study question the generality of the hypothesis that a particular cell invariantly encodes a specific deltat, i.e., that cells have 'characteristic delays'. First, most units tested at more than two frequencies showed maximal responsiveness at different deltat intervals depending upon stimulus frequency. Second, the deltat intervals for maximal responsiveness for half of the units tested were greater than the maximal interaural delays the animal could encounter naturally. Third, deltat functions from the same unit for click and tone stimuli showed poor correspondence. These findings suggest that the encoding of interaural time and intensity might depend on an inter-hemispheric comparison of the activity of neural populations as originally proposed by von Bekesy.

Acoustic Stimulation↗