Auditory processing disorder (APD) is characterized by deficits in the auditory modality that are not due to a global processing problem or to deficiencies in the peripheral auditory system. Diagnosis of APD is time-consuming and could benefit from an objective test. Temporal processing ability is often impaired in cases of APD, which includes deficits on gap detection tasks. Previous attempts to correlate gap detection thresholds to electrophysiological responses have used the P1-N1-P2 response, mismatch negativity (MMN), and 40 Hz auditory steady-state response (ASSR), but these attempts have not been successful, especially using between-channel gap detection tasks. The current study used a modulation gap detection task and recorded the above responses to supra- and subthreshold gaps and stimuli with no gap. A significant P2 response and a later positive peak distinguished perception of a suprathreshold gap. Improvements over previous studies, the relation to auditory training, and limitations and directions for future research are discussed.

No description available.

Hearing in noise is facilitated by the auditory system’s ability to separate sound into small auditory segments. Separation of sound is achieved using an auditory mechanism called temporal resolution that codes for small silent gaps in an acoustic stimulus. This thesis proposes a new method for measuring temporal resolution and applied it to a small pilot group of individuals with tinnitus. Previous studies have postulated that tinnitus can “fill” in silent gaps thereby making gap detection more difficult. This was shown in studies using the gap prepulse inhibition acoustic startle where the amplitude of a startle response indicates the subject’s ability to detect a small silent gap. However studies using behavioural gap detection do not show significant differences in people with reported tinnitus. Thus the behavioural evidence does not appear to support the hypothesis that tinnitus can “fill” in silent gaps. In this thesis a new method was proposed for measuring neural gap detection: the mismatch negativity response (MMN). The mismatch negativity responses were compared to behavioural measures of gap detection in thirty-five normal hearing adults: five with reported tinnitus and thirty without tinnitus. They underwent recordings to gapped stimuli ranging from 2- to 40-ms gap durations. The stimuli were either a broadband or narrowband noise presented in the absence or presence of a filler noise. Results of these experiments found the broadband and narrowband noises elicited MMNs to silent gaps. The amplitude of the MMN increased with larger gap durations. When filled, the amplitude of the entire waveform was proportionally reduced for all gap durations. However, for the tinnitus group the filler reduced the largest gap durations elicited MMNs amplitudes disproportionately more than for the smaller gap durations. The high and low filler noise reduced the amplitude of the 40-ms gap MMNs. This was not reflective in the behavioural performance of gap detection as there were no significant group differences. These studies show that neural gap detection can be measured using mismatch negativities. Reduced behavioural gap detection performance is reflected by a smaller amplitude of the MMN for suprathrehold gaps. This was shown in both normal hearing participants with elevated behavioural gap detection thresholds and participants with tinnitus. Therefore, electrophysiological recordings to gaps may provide further information on the underlying mechanisms involved in impaired gap detection that may not be captured by behavioural measures alone.

No description available.

Objectives: The hypothesis that a natural auditory psychophysical discontinuity contributes to a perceptual category boundary between voiced and voiceless English stop consonants was examined. Design: The relationships between voice onset time (VOT) phonetic boundary and gap-detection thresholds for conditions in which the sounds delimiting the gap were acoustically identical or different were examined in 18 native young adult English speakers. It was specifically hypothesized that between-channel gap-detection thresholds, in contrast to within-channel gap thresholds, would be better predictors of categorical VOT values for listeners. The stimuli used in the between-channel gap-detection task were designed such that dissimilar leading and trailing markers of the gap approximated a stop burst and a following vowel, both in terms of temporal and spectral relationships, while being devoid of phonetic identity. The stimuli used to examine the VOT measure were synthesized bilabial stop syllables in a continuum ranging from /ba/ to /pa/. Results: Statistically significant larger gap thresholds were found for the between-channel conditions than for the within-channel condition (p < 0.05). The center frequency of the trailing marker affected the between-channel gap thresholds with the thresholds improving as the center frequency increased (p < 0.05). Statistically significant positive correlations and predictive linear relations were found between VOT phonetic boundaries and between-channel gap thresholds (p < 0.05) but not within-channel gap thresholds (p > 0.05). Conclusions: A relationship between the phonetic boundary of voiced–voiceless speech sounds and the auditory temporal resolution task of detecting gaps placed within dissimilar markers, regardless of the center frequency of the trailing marker noise burst, was demonstrated. Detection of gaps between different nonspeech acoustic markers and categorical perception of VOT seems to share the same underlying perceptual timing mechanisms in native English speakers.

No description available.

No description available.

Excerpt: It is often the case that veterans who experience hyperacusis have hearing loss and tinnitus; what sets the patient with PTSD apart is an increased likelihood that will rate sound tolerance problems as more severe than tinnitus and hearing loss.

The ability to resolve rapid intensity and frequency fluctuations in sound is important for understanding speech, especially in real-world environments that include background noise and reverberation. Older listeners often complain of difficulties understanding speech in such real-world environments. One factor thought to influence speech understanding in noisy and reverberant environments is temporal resolution, the ability to follow rapid acoustic changes over time. Temporal resolution is thought to help listeners resolve rapid acoustic changes in speech as well as use small glimpses of speech available in the dips or gaps in the background sounds. Temporal resolution is an ability that is known to deteriorate with age and hearing loss, negatively affecting the ability to understand speech in noisy real-world environments. Measures of temporal resolution, including temporal masking, gap detection, and speech in interrupted noise, use a silent gap as the cue of interest. Temporal masking and speech in interrupted noise tasks measure how well a listener resolves a stimulus before, after, or between sounds (i.e., within a silent gap), while gap detection tasks measure how well the listener resolves the timing of a silent gap itself. A listener needs to resolve information within the gap and the timing of the gap when listening to speech in background sounds. This study examined the role of aging and hearing loss on three measures of temporal resolution: temporal masking, gap detection, and speech understanding in interrupted noise. For all three measures, participants were young listeners with normal hearing (n = 8, mean age = 25.4 years) and older listeners with hearing loss (n = 9, mean age = 72.1 years). Results showed significant differences between listener groups for all three temporal measures. Specifically, older listeners with hearing loss had higher temporal masked thresholds, larger gap detection thresholds, and required a higher signal-to-noise ratio for speech understanding in interrupted noise. Relations between temporal tasks were observed. Temporal masked thresholds and gap detection thresholds accounted for a significant amount of the variance in speech-in-noise scores. Findings suggest that deficits in temporal resolution abilities may contribute to the speech-in-noise difficulties reported by older listeners.

No description available.