Biomedical subjects

R C Folsom

Publications and source records attributed to R C Folsom.

36 records · Page 2Linked to original sources

PubMed1995

The development of frequency resolution in humans as revealed by the auditory brain-stem response recorded with notched-noise masking.

Studies of tuning in infants have reported that auditory brain-stem response (ABR) tuning curves generated using low-frequency probes are adultlike by 3 months of age while high-frequency tuning curves remain immature [Folsom and Wynne, J. Acoust. Soc. Am. 81, 412-417 (1987)]. Behavioral studies have similarly reported adultlike low-frequency psychoacoustic tuning curves by 3 months with high-frequency tuning curves immature until approximately 6 months of age [L. Olsho, Infant Behav. Dev. 8, 371-384 (1985); Spetner and Olsho, Child Dev. 61, 632-652 (1990); Schneider et al., J. Exp. Psych.: Human Percept. Perform. 16, 642-652 (1990)]. Prior to this experiment, there have been no ABR studies of the development of frequency resolution for infants older than 3 months. In this study, notched-noise tuning functions were constructed from wave-V amplitude data for 3-month-old, 6-month-old, and adult subjects. Tone-pip stimuli at 1000, 4000, and 8000 Hz (50 dB nHL) were presented simultaneously with notched-noise masking centered at frequencies related to the tone-pip frequency (1/3-oct intervals above and below the probe frequency). By plotting wave-V amplitude across notched-noise center frequency, isointensity tuning functions were generated for the three subject groups at the three probe frequencies. Auditory filter width (Q) and slope (dB/oct) were measured from each notched-noise tuning function in order to qualify degree of tuning. Consistent with previous studies, results showed that 3-month-old infants do not have adultlike tuning for high-frequency stimulation (8000 Hz). In contrast, by 6 months of age, tuning-function width (Q) is adultlike for both high- and low-frequency probes. These results, combined with previously reported evidence that the human cochlea is fully tuned at birth [Abdala et al., submitted to Hear. Res. (1995); Bargones and Burns, J. Acoust. Soc. Am. 83, 1809-1816 (1988)], suggest that immaturities in the auditory-neural system contribute to the broad high-frequency tuning consistently observed in 3-month-old human infants.

Adolescent↗

PubMed1994

The relationship between auditory brainstem response latencies and behavioral thresholds in normal hearing infants and adults.

The relationship between behavioral thresholds and auditory brainstem response (ABR) latencies for 4 and 8 kHz tone pips were examined in normal-hearing 3-month-olds, 6-month-olds and adults. The latencies of waves I and V and the I-V interval of the ABR were analyzed. A linear latency-intensity function was also fit to each subject's latencies for each wave at several levels. The y-intercept of the latency-intensity function was used as a summary measure of latency to examine behavior-ABR correlations. The pattern of age-related change in behavioral threshold was not closely matched by age-related latency reduction for Wave I, Wave V or the I-V interval. However, 3-month-olds with higher behavioral thresholds had longer Wave V latencies and longer I-V intervals than 3-month-olds with lower behavioral thresholds. There was no significant difference in latency between 6-month-olds or adults with higher thresholds and 6-month-olds or adults with lower thresholds. There was also a significant correlation between the Wave V-Wave I latency-intensity intercept difference and behavioral threshold at both 4 and 8 kHz among 3-month-olds. The correlation was not significant among 6-month-olds or adults. These findings suggest that one of the factors responsible for immature behavioral thresholds at 3 months is related to transmission through the auditory brainstem. Because variability in hearing threshold among normal-hearing adults is low, it is not surprising that behavioral threshold is unrelated to ABR latency in this group. However, the lack of such a relationship among 6-month-olds implies that structures central to the auditory brainstem, either sensory or nonsensory, or both, must be responsible for immature behavioral thresholds after 6 months of age.

Acoustic Stimulation↗

PubMed1993

Amplitude-modulation following response (AMFR): effects of modulation rate, carrier frequency, age, and state.

Scalp responses to continuous amplitude-modulated (AM) tones were recorded from adults and 1-month-old infants. The amplitude-modulation following (or envelope) response (AMFR) was quantified using magnitude-squared coherence. This measurement indicates the strength of the frequency-following response relative to background neural noise. The optimal modulation rate for generating the AMFR was determined by studying the effects of stimulus modulation rate on the response. Stimulus AM rate was varied between 10 and 80 Hz for continuous tonal stimuli of 500 Hz, and between 20 and 80 Hz for continuous tonal stimuli of 2000 Hz. Optimal modulation rate was defined as the AM rate that provided the highest coherence estimate. Adult AMFR coherence increased between 10 and 40 Hz (20-40 Hz for 2000 Hz), and decreased between 40 and 80 Hz in both carrier frequency conditions. Infant AMFR coherence, in contrast, monotonically increased between 10 and 80 H (20-80 Hz for 2000 Hz). Thus, within the frequency range examined, 40 Hz is optimal for generating the AMFR in adults, whereas 80 Hz is optimal in infants. Adults were tested while awake and infants were tested during periods of sleep. Given the observed age difference in effective modulation rate, we examined modulation rate effects in a group of adults in both awake and sedated states. As in sleeping infants, 80 Hz was optimal for generating AMFRs in the sedated adults.

Acoustic Stimulation↗

PubMed1993

The relationship between auditory brainstem response and behavioral thresholds in normal hearing infants and adults.

The nature of age-related improvements in auditory sensitivity was explored by comparing behavioral and auditory brainstem response (ABR) thresholds in 3- and 6-month-old infants and in adults. Thresholds were estimated for tone pips at 1, 4, and 8 kHz, presented at a rate of 13.3/s. The time course of development of the two response measures was compared, and the correlation between thresholds for individual subjects was examined. Infant ABR threshold was adultlike at all frequencies, even among 3-month-olds. Infant behavioral thresholds were elevated relative to adult thresholds. Between 3 and 6 months, significant improvement occurred in the 8-kHz behavioral threshold, but no improvement occurred at other frequencies. This difference between ABR and behavioral measures in developmental time course suggests that peripheral sensitivity is not a major determinant of behavioral threshold elevation during infancy. The correlation between behavioral and ABR thresholds was significant at 4 kHz for 3-month-olds and at 8 kHz for adults. This suggests that variability in sensory function at these frequencies contributes to both behavioral and ABR thresholds, although other factors are likely to be involved as well.

Acoustic Stimulation↗

PubMed1992

Auditory responsiveness of premature infants utilizing visual reinforcement audiometry (VRA).

The purpose of this investigation was to study the relationship between visual reinforcement audiometry (VRA) performance and age (i.e., corrected and mental) with 60 premature infants. VRA performance was classified as unacceptable, marginal, or acceptable based on conditionability and number of responses obtained before habituation to the task. The results indicated that mental age and corrected age were significantly related to VRA performance. It was found that a corrected age of 8 mo and/or a mental age of 6 mo is typically required for acceptable performance using VRA. A lack of responsiveness to the VRA procedure at these ages would most likely be due to hearing loss as opposed to a general developmental delay. The data from this study would not support a large scale behavioral hearing screening program for premature infants below 8 mo corrected age or 6 mo mental age.

Acoustic Stimulation↗

PubMed1987

Auditory brain stem responses from human adults and infants: wave V tuning curves.

Decrement in ABR wave V amplitude was measured in the presence of simultaneous tonal maskers. Probe stimuli were 1.0, 4.0, and 8.0-kHz third-octave-filtered clicks. Adults and 3-month-old infants served as subjects. The resultant amplitude-decrement functions for each tonal masker were fit with regression lines. The sound pressure level (SPL) required to reduce wave V to 50% of the unmasked probe amplitude was plotted for each masker to develop tuning curves. The tuning curves were quantified by calculations of tip-to-tail difference, Q 10, and SPL at maximum masker frequency (MMF). Tuning curves for adult and infant subjects were similar for the 1.0-kHz probe. For the high-frequency probes (4.0 and 8.0 kHz), smaller tip-to-tail differences and lower Q 10 values were observed for the infant subjects. Ranges of MMF level were similar across adult and infant subjects. For the 8.0-kHz probe, tuning curves from infant subjects consistently showed maximum masker frequencies which were lower than the probe.

Acoustics↗

PubMed1987

Auditory brainstem responses in young adults with Down syndrome.

Auditory brainstem response (ABR) wave V detection levels, latency, and amplitude were studied in a group of 15 young adults with Down syndrome for whom behavioral measures of hearing sensitivity were also obtained. Comparisons were made to a group of nonretarded control subjects matched by age and sex. Auditory brainstem response detection levels were elevated, response amplitude was reduced, and latency-intensity functions were significantly steeper for the subjects with Down syndrome than for the control group. These findings were associated with a high frequency (8000 Hz) hearing loss prevalent in the otherwise normal-hearing experimental group.

Adolescent↗

PubMed1987

Neurodevelopmental outcome following persistent pulmonary hypertension of the neonate.

The neurodevelopmental status of 12 children with persistent pulmonary hypertension of the newborn (PPHN) was examined. All had neonatal documentation of PPHN by echocardiogram, and all were ventilated at least 72 hours. The mean age at follow-up was 20 months (range, 12-28). Five of the 12 subjects were normal at follow-up, three were felt to be suspect but not clearly abnormal, and four had neurodevelopmental abnormalities, including three with sensorineural hearing impairment (25 per cent incidence in this study). These findings represent a concerning frequency of neurodevelopmental dysfunction and support early routine hearing evaluation in this unique subgroup of neonatal intensive care unit survivors.

Follow-Up Studies↗

PubMed1987

Auditory brainstem responses from human adults and infants: influence of stimulus onset.

Auditory brainstem responses were recorded from adults and 3-month-old infants in response to gated noise bursts of variable rise/fall time. Stimuli were presented at 50 dB nHL for rise/fall times of 0, 1, 2.5, and 5 ms. Acoustic spectra of noise-burst stimuli were identical for all rise/fall conditions. Results show that increases in stimulus rise time were accompanied by increased latency and decreased amplitude of ABR wave V recorded from both adult and infant subjects. Constant differences between adult and infant data were observed across rise/fall conditions for both latency and amplitude values. Adult and infant subjects do not differentially process stimulus onset.

Acoustic Stimulation↗

PubMed1986

Auditory brain stem responses from human adults and infants: restriction of frequency contribution by notched-noise masking.

The frequency contribution to the click-evoked ABR wave V was examined in adults and 3-month-old infants through the use of notch-filtered broadband noise. Notch center frequencies were set at 1.0, 4.0, and 8.0 kHz. Responses were obtained at 20, 40, and 60 dBnHL during the simultaneous presentation of each notched-noise masker as well as in an unmasked condition. The ABR wave V was analyzed for absolute latency and amplitude, as well as latency and amplitude changes resulting from the introduction of masking. Analyses showed wave V latency and amplitude values to be similar for adults and infants within the 1.0-kHz notch. Differences between adult and infant groups were observed as the notch was shifted to the high frequencies. Further, latency and amplitude shifts resulting from the introduction of masking noise produced differential effects on infant responses when compared to adults.

Adult↗

PubMed1985

Auditory brain stem responses from human infants: pure-tone masking profiles for clicks and filtered clicks.

The effects of simultaneous pure-tone maskers on ABR wave V latency and amplitude were examined in three-month-old infants as a means of delineating the frequency specificity of these responses in the immature auditory system. Masking profiles at two intensities (60 and 40 dBn HL) were obtained for click, as well as 4000- and 1000-Hz filtered-click stimuli. Infant profiles, obtained by measuring both latency and amplitude shifts as a result of the discrete-frequency maskers, were compared to adult data obtained under an identical masking paradigm. Both latency and amplitude analyses showed masking profiles for infants which reveal greater low-frequency contribution to responses than found in adult profiles. Additionally, the infant profiles reveal clear differences in the degree of high-frequency spread of masking when comparisons are made to the adult data.

Auditory Perception↗

PubMed1984

A comparison of two conditioning procedures in the use of visual reinforcement audiometry (VRA).

This study compared the effects of two conditioning procedures in the use of visual reinforcement audiometry (VRA) with 1- and 2-year-old high-risk infants. One conditioning procedure used a relatively soft initial stimulus presentation level (30 dB HL) and only two conditioning trials prior to minimum-response-level (MRL) exploration. The other procedure used a 60-dB HL initial presentation level and five conditioning trials prior to MRL exploration. Results indicated no significant differences between conditioning procedures in regard to obtained MRLs, number of stimulus presentations required to establish MRL (discounting conditioning trials), and number of false-positive responses observed during control trials. Age was a significant factor only in regard to the number of stimulus presentations required to establish MRL. 2-year-olds required fewer presentations than 1-year-olds. Results are discussed in relation to the auditory stimulus used to obtain responses and in regard to individual clinical circumstances which may dictate the use of one procedure over the other.

Acoustic Stimulation↗

PubMed1984

Frequency specificity of human auditory brainstem responses as revealed by pure-tone masking profiles.

The frequency specificity of the auditory brainstem response (ABR) was examined by means of pure-tone masking profiles using click, 4000-Hz, and 1000-Hz filtered-click stimuli. Simultaneous pure-tone maskers were presented at one-half octave intervals around stimulus center frequency. Masking profiles at two intensities (60 and 40 dB SL) were obtained by measuring both latency and amplitude shifts in wave V as a result of the discrete-frequency maskers. Both latency and amplitude analyses showed masking profiles at 40 dB SL that were narrow and centered around stimulus frequency, whereas profiles at 60 dB SL showed high-frequency spread of the cochlear excitation area.

Acoustic Stimulation↗

PubMed1983

Auditory brain-stem responses in infants with Down's syndrome.

Auditory brain-stem responses to clicks were recorded from 38 infants with Down's syndrome at the ages of 3, 6, and 12 months in an attempt to delineate age-dependent and intensity-dependent latency changes in this population. Comparisons were made with 35 normally developing infants at the same age levels. Significant wave V latency differences were observed between groups for both age and intensity, with the group with Down's syndrome showing, in general, shorter absolute wave V latency values across age and steeper latency functions across intensity. The implications of this study are as follows: (1) latency-intensity curves for normally developing infants will not serve adequately as normative values for infants with Down's syndrome, particularly at the age of 12 months, and (2) cochlear function in infants with Down's syndrome may differ from normal infants by the age of 12 months.

Acoustic Stimulation↗

PubMedDate not supplied

Reinforced and nonreinforced head-turn responses of infants as a function of stimulus bandwidth.

The purpose of this study was to investigate auditory-stimulus effects on head-turn response behavior of infants under conditions where responses were either reinforced or not reinforced with a visual stimulus. The auditory stimuli contained different frequency bandwidths between 2000 and 4000 Hz. The stimulus with the widest bandwidth resulted in more responses than the other two stimuli in the no-reinforcement condition. When conditioning was established and all responses were visually reinforced, there was no difference in response behavior among stimulus groups for either suprathreshold or threshold stimulation. These findings have implications for clinical assessment using visual reinforcement audiometry. Results suggest that bandwidth characteristics of the auditory stimulus have no influence on response behavior of infants providing conditioning can be established and maintained through the use of visual reinforcement.

Audiometry↗

PubMedDate not supplied

Auditory brainstem responses in children with early recurrent middle ear disease.

Auditory brainstem responses were recorded from an experimental group of 15 children with early histories of recurrent middle ear disease for the purpose of examining the effects of reduced auditory input on auditory brainstem function. The responses from these children were analyzed in terms of absolute latencies, interwave latencies and latency shifts across sensation level. Comparisons were made to a control group of children with no history of middle ear disease. Results indicated significant differences between the groups. The experimental group demonstrated greater absolute latencies for waves III and V as well as greater interwave latencies. These findings support the interpretation of an association between early recurrent middle ear disease and brainstem function.

Auditory Pathways↗

PubMedDate not supplied

N1 action potentials in humans. Influence of simultaneous contralateral stimulation.

N1 action potentials, elicited by low-level, 4.0-kHz filtered clicks, were recorded from the ear canals of normal-hearing adults. Responses were recorded at two sensation levels in the presence and absence of a pure tone delivered to the contralateral ear. Waveforms were analysed for changes in amplitude and latency. A significant reduction in the amplitude of N1 was observed following the introduction of the contralateral tone at both FC levels. A concomitant change in latency was not observed. For all subjects, ipsilateral and contralateral signals were below the intensities which resulted in acoustic reflexes and crossover of contralateral signals. These data suggest that the N1 amplitude reduction observed in this study represents inhibitory activity of the efferent auditory pathway.

Acoustic Stimulation↗

PubMedDate not supplied

Brainstem wave V latencies to tone pip stimuli.

The present study was undertaken to examine the feasibility of using tone pip stimuli rather than conventional clicks in brainstem evoked response (BER) audiometry. Trains of 2000-Hz tone pips, 4000-HZ tone pips or clicks were presented at seven intensity levels to six normal young adults. Results demonstrated that BERs can be readily elicited by tone pips. This latter finding may be attributable to the differences in stimulus rise times. Tone pips appear to introduce greater frequency specificity to BER audiometry without a marked loss in the ability to elicit the response.

Acoustic Stimulation↗