Dennis T. Ries

Safety and clinical performance of acoustic reflex tests.

OBJECTIVE Safety and effectiveness of acoustic reflex tests are important issues because these tests are widely applied to screen for retrocochlear pathology. Previous studies have reported moderately high sensitivity and specificity for detection of acoustic neuroma. However, there have been reports of possible iatrogenic hearing loss resulting from acoustic reflex threshold (ART) and decay (ARD) tests. This study assessed safety and clinical performance of ART tests for detection of acoustic neuroma. DESIGN We report a case in which ARD testing resulted in a significant bilateral permanent threshold shift. This case was the impetus for us to investigate the clinical utility of ART and ARD tests. We analyzed sensitivity and specificity of ART, as well as asymmetry in pure-tone thresholds (PTT) for detection of acoustic neuroma in 56 tumor and 108 non-tumor ears. RESULTS AND CONCLUSIONS Sensitivity and specificity were higher for PTT asymmetry than for ART. Ipsilateral ART at 1000 Hz had poor sensitivity and specificity for detection of acoustic neuroma, and involves some potential risk to residual hearing for presentation levels higher than 115 dB SPL. Approximately half of the acoustic neuroma group had ipsilateral ARTs that would require administration of ARD tests at levels exceeding 115 dB SPL. Therefore, we conclude that PTT asymmetry is a more effective test for detection of acoustic neuroma, and involves no risk to residual hearing. Future studies of contralateral reflex threshold and ARD in combination with PTT asymmetry are recommended.

Basilar membrane nonlinearity and loudness

Loudness matching functions for tones for persons with one shifted-threshold ear (hearing loss and noise-shifted thresholds) and one ear within normal limits were used to derive the presumed basilar membrane (BM) input-output (I/O) function in a normal ear. The comparison was made by assuming that the BM I/O function for the ear with the cochlear threshold shift has a slope of one (a linearized cochlea). The function for the normal ear was derived from the loudness matching function based on this assumption. Comparisons were made for archival basilar membrane data [M. A. Ruggero, N. C. Rich, A. Recio, S. S. Narayan, and L. Robles, J. Acoust. Soc. Am. 101, 2151-2163 (1997)] for chinchilla and archival loudness matches for long-duration tones for persons with various degrees of cochlear hearing loss [F. Miskolczy-Fodor, J. Acoust Soc. Am. 32, 486-492 (1960)]. Comparisons were made also between BM I/O functions and ones derived from loudness matches for persons with unilateral hearing loss simulated by broadband noise. The results show a close resemblance between the basilar membrane I/O function and the function derived from loudness matches for long-duration tones, even though the comparison was between human and chinchilla data. As the degree of threshold shift increases from 40 to 80 dB, the derived BM I/O functions become shallower, with slopes for losses of 60 dB or more falling in the range of values reported for physiological data. Additional measures with short-duration tones in noise show that the slope of the loudness function and the slope of the derived basilar membrane I/O function are associated with the behavioral threshold for the tone. The results for long-duration tones suggest a correspondence between BM displacement and loudness perception in cases of recruitment, but the relation between the degree of loss and the amount of BM compression and the relation between signal duration and compression suggests that other factors, such as the neural population response, may play a role.

Masker laterality and cueing in forward-masked intensity discrimination

Forward-masked intensity discrimination was measured as a function of level in experiments designed to reveal insights into the mechanism(s) underlying the midlevel elevation of the Weber fraction. The standard and maskers were 1.0-kHz tones that were separated by 100 ms. Performance was measured for listeners with normal hearing using an adaptive procedure. In experiment 1, intensity discrimination was measured in the presence of an ipsilateral masker (80 dB SPL), a contralateral masker (93 dB SPL), and a binaural (dichotic) masker produced by combining the ipsilateral and contralateral maskers. Listeners perceived only the contralateral masker in the binaural-masker condition. The contralateral masker produced a small midlevel elevation of the Weber fraction. The ipsilateral masker and the binaural masker produced a large, midlevel elevation of the Weber fraction. Experiment 2 found that a two-tone masker resulted in a reduction (improvement) in the Weber fraction for some conditions, but the midlevel elevation remained for all subjects in this cue-tone condition. Experiment 3 demonstrated that cross talk could not account for all of the masking observed with contralateral maskers. Taken together, the results suggest that a single complex mechanism or multiple mechanisms may be responsible for the masking seen in these experiments. On the basis of the cueing results, it is concluded that a portion of the masking is due to cognitive factors; however, a sensory mechanism cannot be ruled out for the remaining portion, based on the results of these experiments. Finally, a small but significant amount of masking due to contralateral maskers places the mechanism for this outcome central to the cochlear nucleus.

Effects of recurrent tonal information on auditory working memory for pitch

This study ascertained the influence of repeating pitch information within an intervening tonal sequence upon the extent of interference for a pitch standard held within auditory working memory as measured by the difference limen for frequency (DLF). Standard and comparison tones were presented to subjects and same/different responses were obtained using a touch screen monitor and the DLF was measured using single interval adjustment matrix (SIAM) procedure [Kaernbach, C., 1990. A single-interval adjustment-matrix (SIAM) procedure for unbiased adaptive testing. J. Acoust. Soc. Am. 88, 2645-2655]. Estimates of the DLF were obtained in a control condition with a silent inter-comparison interval and three conditions containing intervening tones within the temporal gap between the standard and comparison stimuli. The presence of intervening stimuli produced a significant increase in the DLF when the intervening tonal sequence contained tones with pitches that differed from that of the standard (Int condition) as well as when the sequence contained a tone with a pitch identical to that of the comparison (RptCmp condition). Further, the DLFs obtained for RptCmp condition were significantly higher than those measured in the Int condition. The DLFs measured in the condition where the pitch of an intervening tone was identical to the standard were significantly lower than those for the Int and RptCmp condition, but did not differ from the DLFs for the control condition. These results indicate that either a release from or an increase in interference in auditory working memory for pitch can occur dependent upon the frequency relationships between of the standard, comparison, and intervening tones.

Effect of interaural level and phase cues on intervening interference in auditory working memory for loudness

The focus of this study was to gauge the influence of intervening interference on an intensity standard held within auditory working memory through measurement of the just noticeable difference (JND) for intensity. Additionally, the use of interaural phase differences and interaural level differences as spatial cues were employed to identify whether these indicators provided a means for release from interference. A series of tones, both with and without spatial cues, were presented to subjects and responses were obtained using the method of constant stimuli. The JND for intensity was measured in a control condition with a silent inter-comparison interval and three conditions containing intervening tones within the temporal gap between the standard and comparison stimuli. The presence of intervening interference produced a significant increase in the intensity difference needed for discrimination. Further, the provision of spatial cues did not result in a significant release from this interference. These results indicate that a release from interference is not obtained when listeners are required to rely entirely on information used for spatial location (i.e., overall intensity differences and interaural phase/intensity differences) without unique information identifying the sound source to aid in retention of relevant information within auditory working memory.

The effects of intervening interference on working memory for sound location as a function of inter-comparison interval.

This study examined the effects of inter-comparison interval duration and intervening interference on auditory working memory (AWM) for auditory location. Interaural phase differences were used to produce localization cues for tonal stimuli and the difference limen for interaural phase difference (DL-IPD) specified as the equivalent angle of incidence between two sound sources was measured in five different conditions. These conditions consisted of three different inter-comparison intervals [300 ms (short), 5000 ms (medium), and 15,000 ms (long)], the medium and long of which were presented both in the presence and absence of intervening tones. The presence of intervening stimuli within the medium and long inter-comparison intervals produced a significant increase in the DL-IPD compared to the medium and long inter-comparison intervals condition without intervening tones. The result obtained in the condition with a short inter-comparison interval was roughly equivalent to that obtained for the medium inter-comparison interval without intervening tones. These results suggest that the ability to retain information about the location of a sound within AWM decays slowly; however, the presence of intervening sounds readily disrupts the retention process. Overall, the results suggest that the temporal decay of information within AWM regarding the location of a sound from a listeners environment is so gradual that it can be maintained in trace memory for tens of seconds in the absence of intervening acoustic signals. Conversely, the presence of intervening sounds within the retention interval may facilitate the use of context memory, even for shorter retention intervals, resulting in a less detailed, but relevant representation of the location that is resistant to further degradation.

Intensity discrimination of ramped and damped tones

Intensity discrimination of 1.0‐kHz tones that had exponentially ramped or damped envelopes was measured as a function of duration and level. Standard levels ranged from near threshold to 90 dB SPL and durations ranged from 10 to 200 ms. Just‐noticeable differences for some subjects were smaller for damped tones than for ramped tones for the same duration and level. For these conditions, damped tones showed more temporal integration than ramped tones. This result is somewhat surprising given that the subjective duration of ramped tones increased by a factor of 100 for stimuli ranging from 10 to 200 ms, whereas the subjective duration of damped tones increased by a much smaller factor of 28 over the same range of durations. Possible physiological and cognitive explanations for these differences will be discussed. [Work supported by NIH‐NIDCD R29 DC01542.]

Retention of gap length in normal-hearing listeners.

Listener retention of silent, gap-length duration was studied. Just noticeable differences (JNDs) for gap length within standard and comparison stimuli were obtained for intervals with and without intervening noise bursts, including a condition with gapped intervening bursts. Outcomes indicate that gap duration itself can be determinant. Also, JNDs were similar whether intervening stimuli were present or absent, differing from results reported for pitch, loudness, and timbre retention. The latter suggests additional/alternative cortical resources might be employed for retention of auditory–temporal information.

The effects of intervening interference on working memory for sound location.

Inter‐aural phase differences were used to study working memory for perceived auditory position quantified as a change in the difference limen (DL) in equivalent auditory angle across 300‐, 5000‐, and 15 000‐ms retention intervals. Data were obtained for the medium and long intervals both in the presence and absence of intervening tones. Intervening stimuli within the medium and long inter‐comparison intervals produced a significant increase in the DLs compared those obtained in the corresponding quiet conditions. The DL for the 300‐ms interval was roughly equivalent to that obtained for the medium interval without intervening tones while that obtained for 15 000‐ms interval was significantly greater than that obtained for either of the shorter intervals. The results suggest that the temporal decay of information within AWM of a listerner regarding the location of a sound within their environment is so gradual that it can be maintained in trace memory for tens of seconds in the absence of intervening acou...

Relationships among musical training and pitch matching in children and adults

This experiment attempted to determine if individuals with extensive musical training’s pitch perception and memory were more resistant to degradation (e.g., time and interference) than that of individuals with limited musical training. It is known that musical training influences cortical sound processing through learning-based processes, but also at the preattentive level within the brainstem. Pitch memory abilities were investigated in 66 participants with no known hearing, attention, or cognitive impairment. Participants were placed into subgroups based on age (young children, older children, and adults) and their self-reported musical training experience. Two experiments measuring auditory perception and memory skills for pitch were collected, the pitch pattern span (PPS; Weaver, DiGiovanni, & Ries, 2015) and a pitch matching retention task based on Ross, Olsen, and Gore’s procedure (2003). We found that individuals with greater musical training exhibited enhanced pitch perception and memory processe...