Biomedical subjects

C W Ponton

Publications and source records attributed to C W Ponton.

7 recordsLinked to original sources

PubMed1992

Frequency-specific maturation of the eighth nerve and brain-stem auditory pathway: evidence from derived auditory brain-stem responses (ABRs).

Previous studies of human auditory development using frequency-specific auditory brain-stem responses (ABRs) have reported that maturation for both peak and interpeak latencies occurs earlier for responses generated by low-frequency stimuli. In two of these studies, low-frequency ABRs presumed to originate from apical locations in the cochlea were likely dominated by activity from higher frequency regions closer to the base. In the present study, the high-pass noise-masking technique was used to generate derived ABRs that represent activity from isolated place specific regions along the basilar membrane. Analysis of auditory brain-stem maturation based on I-V interpeak latency differences with adult means revealed a frequency-specific pattern of development. Developmental changes occurred faster and mature function was attained earlier for ABRs from the mid-center-frequency (CF) derived conditions than from either the highest or lowest CF derived conditions. The differential maturation of mid-CF derived ABRs may reflect the delayed effects of the pattern of development that occurs in the cochlea.

Auditory Pathways↗

PubMed1992

Place-specific derived cochlear microphonics from human ears.

The high-pass noise masking technique was used to obtain derived frequency-specific cochlear microphonics (CM) from subtracted waveforms to rarefaction and condensation stimuli recorded with a tympanic membrane electrode. Two characteristics suggest that the response is place-specific CM: the derived response retains the same frequency as the stimulating toneburst and the response follows the stimulus polarity. For click stimulation, derived neural responses make the place-specific CM difficult to observe except in the 2-1 kHz derived band. In contrast, place-specific CM evoked by 0.5 and 1 kHz tonebursts can usually be detected in at least three derived bands. The amplitude of the response is largest in the derived band with center-frequency (CF) just above that of the toneburst. This discovery of a place-specific CM offers the possibility of assessing (outer) hair cell function in the apical part of the human cochlea.

Acoustic Stimulation↗

PubMed1991

Assessment of cisplatin-induced ototoxicity using derived-band ABRs.

Ototoxicity is an adverse side effect of numerous therapeutic agents (amino-glycoside antibiotics, blood chelating agents, diuretics and oncologic drugs) used in treatment of both adult and pediatric patients. Recently, there has been increasing interest in using the auditory brainstem response (ABR) to detect both short-term effects of ototoxicity in adults and long-term effects of drug administration on neonates and children. Since click ABRs have relatively poor frequency selectivity they best approximate the pure-tone hearing threshold in the 2000-4000 Hz frequency range. Hearing loss above or below that frequency range can be present without producing significant abnormalities in the ABR waveform parameters. Frequency-specific ABRs can be obtained using the derived response technique. The purpose of this study was to investigate early cisplatin ototoxicity using both the broadband click and derived ABR and to monitor progressive hearing loss with repeated drug trials in 18 patients studied over a 2-year period. ABRs were obtained serially prior to and following intravenous administration of cisplatin. Derived ABRs were found to be more sensitive than broadband click ABR in detecting early high-frequency hearing loss. For click ABRs, the cumulative dosage of cisplatin at age of ABR examination was correlated with hearing loss in only those patients under 3 years of age. No significant correlation was found between cumulative cisplatin dosage when tested and degree of hearing loss in those patients over 3 years of age.

Adolescent↗

PubMed1991

Maturation of the traveling-wave delay in the human cochlea.

The maturation of the traveling-wave delay in the human cochlea was investigated in 227 subjects ranging in age from 29 weeks conceptional age to 49 years by using frequency specific auditory brain-stem responses (ABRs). The derived response technique was applied to ABRs obtained with click stimuli (presented at a fixed level equal to 60-dB sensation level in normal hearing adults) in the presence of high-pass noise masking (slope 96 dB/oct) to obtain frequency specific responses from octave-wide bands. The estimate of traveling-wave delay was obtained by taking the difference between wave I latencies from adjacent derived bands. It was found that the traveling-wave delay between the octave band with center frequency (CF) of 11.3 kHz and that with CF of 5.7 kHz decreased (about 0.4 ms on average) in exponential fashion with age to reach adult values at 3-6 months of age. This decrease was in agreement with reported data in kitten auditory-nerve fibers. The traveling-wave delays between adjacent octave bands with successive lower CF did not change with age.

Adolescent↗

PubMed1991

Frequency dependent maturation of the cochlea and brainstem evoked potentials.

The anatomical development of the human cochlea starts in the middle basal turn and progresses both toward the base and the apex. Behavioral responses, in contrast, appear to emerge for lower frequencies first. Cochlear tuning may continue to change during early development and so effect electrophysiological and behavioral measures of maturation. The maturation of the cochlear traveling wave delay as well as the ABR I-V interval was investigated using the derived response technique which permits a frequency dependent analysis of this maturation. It was found that the traveling wave delay decreased significantly with age for the most basal part of the cochlea; however, it was not affected by age for more apical locations. The I-V delay difference with the adult values was found significantly shorter in the derived octave band with CF = 2.8 kHz than in all other bands for the preterm, term and infant groups. This suggests that the frequency dependent electrophysiological maturation of the brainstem parallels the anatomical development of the cochlea.

Acoustics↗

PubMed1987

Enhanced articulatory speed in ambidexters.

The possibility that incomplete speech lateralization might be related to reduced articulatory speed was investigated in two studies with normal, young adults. Contrary to expectations, speech was produced faster by ambidextrous subjects than by either strongly left- or strongly right-handed subjects under a number of conditions. However, there were no differences in speech lateralization between these groups when lateralization was measured using dichotic listening scores. In a second study, the superiority of ambidextrous subjects was found to extend to certain manual movement tasks as well.

Adult↗

PubMed1986

Programs to produce high quality dichotic tapes for central auditory testing.

Dichotic stimulation, the simultaneous presentation of two different acoustic signals to the right and left ears, respectively, is used routinely in the clinical assessment of speech lateralization as well as in other central auditory testing procedures in the clinic and laboratory. At present, most researchers and clinicians depend on a few commercial sources for dichotic tapes, because there are a limited number of facilities which are able to produce such tapes. Moreover, some of the commercial tapes currently offered for sale contain important stimulus errors. In the present paper, we describe a general set of programs for the PDP 11 series of computers, which permits sequences of dichotic stimuli to be generated and output with a high degree of precision. These programs therefore allow researchers to generate any desired sequence of dichotic stimulation, for recording and taping, for use in their research. The programs operate in two stages to generate the required dichotic sequences. In the first stage, the constrained random ordering of the stimuli is generated as specified by the user. In the second stage, after the preliminary stimulus preparation has been completed (for example, using a waveform editing package; cf., D.G. Jamieson and D. A. Naugler, Comput. Biomed. Res., 1985, 18, 480), an audio tape is generated with stimuli presented dichotically, with timing and sequencing precisely as specified.

Auditory Cortex↗