Biomedical subjects

Kelly L Tremblay

Publications and source records attributed to Kelly L Tremblay.

10 recordsLinked to original sources

PubMed2006

Neural representation of amplified speech sounds.

OBJECTIVE: To determine if (1) evoked potentials elicited by amplified speech sounds (/si/ and /[symbol: see text]/) can be recorded reliably in individuals, (2) amplification alters neural response patterns, and (3) different amplified speech sounds evoke different neural patterns. DESIGN: Cortical evoked potentials were recorded in sound field from seven normal-hearing young adults in response to naturally produced speech tokens /si/ and /[symbol: see text]/ from the Nonsense Syllable Test. With the use of a repeated-measures design, subjects were tested and then retested within an 8-day period in both aided and unaided conditions. RESULTS: (1) Speech-evoked cortical potentials can be recorded reliably in individuals in both aided and unaided conditions. (2) Hearing aids that provide a mild high-frequency gain only subtly enhance peak amplitudes relative to unaided cortical recordings. (3) If the consonant-vowel boundary is preserved by the hearing aid, it can also be detected neurally, resulting in different neural response patterns for /si/ and /[symbol: see text]/. CONCLUSIONS: Speech-evoked cortical potentials can be recorded reliably in individuals during hearing aid use. A better understanding of how amplification (and device settings) affects neural response patterns is still needed.

Acoustic Stimulation↗

PubMed2006

Acoustic change complexes recorded in adult cochlear implant listeners.

OBJECTIVES: The objectives of this study were to determine: 1) whether the acoustic change complex (ACC) could be reliably recorded in cochlear implant listeners and, 2) whether different speech sounds evoke distinct ACC patterns. DESIGN: Eight adults wearing the Nucleus-24 cochlear implant (CI) were tested using naturally produced speech tokens /si/ and /i/. Stimuli were tokens from the standardized UCLA version of the Nonsense Syllable Test. Using a repeated-measures design, participants were tested and retested within a 3-wk period. RESULTS: Intraclass correlation coefficients for grand mean and individual-response waveforms recorded from the syllables /si/ and /i/ ranged from 0.63 to 0.89 from test to retest. Also, ACC latencies signaling the onset of a vowel in /i/ were significantly earlier than those evoked by /si/. CONCLUSIONS: The ACC can be reliably recorded in individuals wearing CI. Furthermore, the naturally produced speech syllables /si/ and /i/ evoke distinct ACC patterns. Because of its good stability and the ease with which it can be recorded in individual CI listeners, the ACC can be evoked using complex signals (such as naturally produced speech syllables) when studying central auditory function in CI listeners.

Acoustic Stimulation↗

PubMed2006

New perspectives on assessing amplification effects.

Clinicians have long been aware of the range of performance variability with hearing aids. Despite improvements in technology, there remain many instances of well-selected and appropriately fitted hearing aids whereby the user reports minimal improvement in speech understanding. This review presents a multistage framework for understanding how a hearing aid affects performance. Six stages are considered: (1) acoustic content of the signal, (2) modification of the signal by the hearing aid, (3) interaction between sound at the output of the hearing aid and the listener's ear, (4) integrity of the auditory system, (5) coding of available acoustic cues by the listener's auditory system, and (6) correct identification of the speech sound. Within this framework, this review describes methodology and research on 2 new assessment techniques: acoustic analysis of speech measured at the output of the hearing aid and auditory evoked potentials recorded while the listener wears hearing aids. Acoustic analysis topics include the relationship between conventional probe microphone tests and probe microphone measurements using speech, appropriate procedures for such tests, and assessment of signal-processing effects on speech acoustics and recognition. Auditory evoked potential topics include an overview of physiologic measures of speech processing and the effect of hearing loss and hearing aids on cortical auditory evoked potential measurements in response to speech. Finally, the clinical utility of these procedures is discussed.

Acoustic Stimulation↗

PubMed2006

Effect of probe tube insertion depth on spectral measures of speech.

This study investigated how depth variations in the tip of the probe tube affected spectral measures of speech recorded in the external ear canal. Consonant-vowel nonsense syllables were recorded with a probe tube microphone system in 10 adult participants with normal middle ear function. Recordings were made with the probe tube tip placed 1 mm, 5 mm, and 10 mm beyond the medial tip of a custom earmold. The effect of probe depth was evaluated on spectral levels (one-third octave and one- twelfth octave band). Extending the probe tube 10 mm past the medial tip of the earmold gave the most accurate results, with relatively lower sound levels for either the 1-mm or 5-mm insertion depth. In general, the effect of insertion depth was minimal at frequencies below 3 to 4 kHz, although this varied with the specific phoneme and the width of the analysis bands. The authors found no significant difference between 1- and 5-mm insertion depths, suggesting that as long as the tip of the probe tube is sufficiently close to the tympanic membrane to capture the highest frequency of interest, it makes little difference if it is less than 5 mm beyond the earmold tip.

Acoustic Stimulation↗

PubMed2006

The neural representation of consonant-vowel transitions in adults who wear hearing AIDS.

Hearing aids help compensate for disorders of the ear by amplifying sound; however, their effectiveness also depends on the central auditory system's ability to represent and integrate spectral and temporal information delivered by the hearing aid. The authors report that the neural detection of time-varying acoustic cues contained in speech can be recorded in adult hearing aid users using the acoustic change complex (ACC). Seven adults (50-76 years) with mild to severe sensorineural hearing participated in the study. When presented with 2 identifiable consonant-vowel (CV) syllables ("shee" and "see"), the neural detection of CV transitions (as indicated by the presence of a P1-N1-P2 response) was different for each speech sound. More specifically, the latency of the evoked neural response coincided in time with the onset of the vowel, similar to the latency patterns the authors previously reported in normal-hearing listeners.

Aged↗

PubMed2004

Speech evoked cortical potentials: effects of age and stimulus presentation rate.

We examined the effects of stimulus complexity and stimulus presentation rate in ten younger and ten older normal-hearing adults. A 1 kHz tone burst as well as a speech syllable were used to elicit the N1 -P2 complex. Three different interstimulus intervals (ISI) were used (510, 910, and 1510 msec). When stimuli were presented at the medium presentation rate (910 msec ISI), N1 and P2 latencies were prolonged for older listeners in response to the speech stimulus but not the tone stimulus. These age effects were absent when stimuli were presented at a slower rate (1510 msec ISI). Results from this study suggest that rapidly occurring stimulus onsets, either within a stimulus or between stimuli, result in prolonged N1 and P2 responses in older adults. This is especially true when processing complex stimuli such as speech. One potential explanation for this age effect might be age-related refractory differences in younger and older auditory systems. Refractory issues might in turn affect synchronized neural activity underlying the perception of critical time-varying speech cues and may partially explain some of the difficulties older people experience understanding speech.

Acoustic Stimulation↗

PubMed2003

Effects of age and age-related hearing loss on the neural representation of speech cues.

OBJECTIVE: To examine the effects of aging and age-related hearing loss on the perception and neural representation of a time-varying speech cue. METHODS: P1, N1 and P2 cortical responses were recorded from younger and older normal-hearing adults, as well as older adults with age-related hearing loss. Synthetic speech tokens representing 10 ms increments along a /ba/-/pa/ voice-onset-time (VOT) continuum were used to evoke the responses. Each participant's ability to discriminate the speech tokens was also assessed. RESULTS: Compared with younger participants, older adults with and without hearing loss had more difficulty discriminating 10 ms VOT contrasts. In addition, both older groups elicited abnormal neural response patterns. There were no significant age-related findings for P1 latency; however, N1 latencies were prolonged for both older groups in response to stimuli with increased VOT durations. Also, P2 latencies were delayed for both older groups. The presence of age-related hearing loss resulted in a significant increase in N1 amplitude in response to voiceless stimuli. CONCLUSIONS: Aging and age-related hearing loss alter temporal response properties in the central auditory system. Because both older groups had difficulty discriminating these same speech stimuli, we conclude that some of the perceptual difficulties described by older adults might be due to age-related changes regulating excitatory and inhibitory processes. SIGNIFICANCE: Some of the speech understanding difficulties expressed by elderly adults may be related to impaired temporal precision in the aging auditory system. This might explain why older adults frequently complain that wearing a hearing aid makes speech louder, but does not necessarily improve their ability to understand speech.

Acoustic Stimulation↗

PubMed2003

Effects of decreased audibility produced by high-pass maskers in younger and older adults.

A recurring problem in aging research is separating the effects of age per se from the effects of high-frequency hearing loss. One approach is to present test stimuli in the presence of a high-pass masker to control confounding differences in high-frequency audibility across age groups. However, there is evidence that such maskers may affect older and younger listeners differently. In this study, pure-tone thresholds were measured for younger and older listeners in the presence of high-pass maskers. The age groups were carefully selected based on similar unmasked thresholds at each frequency. Thresholds were measured in quiet and in seven masker conditions. Both younger and older listeners showed increased threshold shift below the masker passband as the masker level increased. The degree of threshold shift was not greater for older versus younger listeners. Results suggest that high-pass maskers may be used to reduce high-frequency sensitivity differences between younger and older listeners without introducing differential masking effects.

Adult↗

PubMed2002

Aging alters the neural representation of speech cues.

Age-related deficits in speech understanding are well documented. Because speech is a complex signal, containing time-varying acoustic cues, it is frequently hypothesized that aging adversely affects the ability to process temporal cues. This study examined the neural representation and perception of voice-onset-time, a temporal cue that distinguishes voiced /b/ from voiceless /p/ sounds. We found that older adults had more difficulty than younger listeners discriminating voice-onset contrasts. In addition, these same speech stimuli evoked abnormal neural responses in older adults. That is, compared with younger listeners, N1 and P2 long-latency auditory evoked responses were prolonged for older adults. Collectively, these results suggest speech perception difficulties described by older adults may be related to age-related changes regulating excitatory and inhibitory processes.

Adult↗

PubMed2002

Auditory training induces asymmetrical changes in cortical neural activity.

Pre-attentive cortical evoked potentials reflect training-induced changes in neural activity associated with speech-sound training. Seven normal-hearing young adults were trained to identify two synthetic speech variants of the syllable /ba/. As subjects learned to correctly identify the two stimuli, changes in P1, N1, and P2 amplitudes were observed. Of particular interest is that P1, N1, and P2 components of the N1-P2 complex responded differently to listening training. That is, significant changes in P1 and N1 amplitude were recorded over the right but not the left hemisphere. In contrast, increases in P2 were observed bilaterally. These results indicate that training-related changes in neural activity are reflected in far-field aggregate neural responses and that distinct patterns of neural change, perhaps reflecting hemispheric specialization, likely represent different aspects of auditory function.

Acoustic Stimulation↗