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PubMed1992

The psychophysics of concurrent sound segregation.

To perceptually separate concurrent complex sounds, normally hearing listeners simultaneously combine information across a wide range of frequency components. Three psychoacoustical experiments are described which investigate different forms of this across-frequency processing. The first two experiments investigate the role of coherence of frequency modulation (FM) between widely separated frequency components of a complex sound. The first experiment bolsters existing evidence that, for harmonic sounds, listeners can discriminate coherent from incoherent FM, but only by detecting the mistuning that arises from incoherent FM. The second demonstrates that, for inharmonic sounds, coherence of FM has no effect on the phenomenon of modulation detection interference (see Moore & Shailer, this symposium) once within-channel cues (combination tones and beating) are masked by background noise. It is concluded that there is not an across-frequency mechanism specific to the detection of FM incoherence. The third experiment investigates the extent to which the detection of mistuning of one component of a harmonic complex is impaired by an interfering sound (the 'interferer') with a frequency spectrum similar to that of the mistuned component. When the interferer is gated on and off with the harmonic complex, it has only a small effect provided that its level is more than 3 dB below that of the target. However, when the interferer starts before and ends after the complex, thresholds are elevated more, and this elevation occurs even for low-level interferers. Explanations of this effect in terms of adaptation and of auditory streaming are discussed.

Acoustic Stimulation↗
PubMed2003

Informational masking: counteracting the effects of stimulus uncertainty by decreasing target-masker similarity.

Previous work has indicated that target-masker similarity, as well as stimulus uncertainty, influences the amount of informational masking that occurs in detection, discrimination, and recognition tasks. In each of five experiments reported in this paper, the detection threshold for a tonal target in random multitone maskers presented simultaneously with the target tone was measured for two conditions using the same set of five listeners. In one condition, the target was constructed to be "similar" (S) to the masker; in the other condition, it was constructed to be "dissimilar" (D) to the masker. The specific masker varied across experiments, but was constant for the two conditions. Target-masker similarity varied in dimensions such as duration, perceived location, direction of frequency glide, and spectro-temporal coherence. Group-mean results show large decreases in the amount of masking for the D condition relative to the S condition. In addition, individual differences (a hallmark of informational masking) are found to be much greater in the S condition than in the D condition. Furthermore, listener vulnerability to informational masking is found to be consistent to at least a moderate degree across experiments.

Acoustic Stimulation↗
PubMed2006

Temporal processing deficits in the pre-senescent auditory system.

This study tested the hypothesis that temporal processing deficits are evident in the pre-senescent (middle-aged) auditory system for listening tasks that involve brief stimuli, across-frequency-channel processing, and/or significant processing loads. A gap duration discrimination (GDD) task was employed that used either fixed-duration gap markers (experiment 1) or random-duration markers (experiment 2). Independent variables included standard gap duration (0, 35, and 250 ms), marker frequency (within- and across-frequency), and task complexity. A total of 18 young and 23 middle-aged listeners with normal hearing participated in the GDD experiments. Middle age was defined operationally as 40-55 years of age. The results indicated that middle-aged listeners performed more poorly than the young listeners in general, and that this deficit was sometimes, but not always, exacerbated by increases in task complexity. A third experiment employed a categorical perception task that measured the gap duration associated with a perceptual boundary. The results from 12 young and 12 middle-aged listeners with normal hearing indicated that the categorical boundary was associated with shorter gaps in the young listeners. The results of these experiments indicate that temporal processing deficits can be observed relatively early in the aging process, and are evident in middle age.

Adolescent↗
PubMed2006

Dead regions in the cochlea and enhancement of frequency discrimination: Effects of audiogram slope, unilateral versus bilateral loss, and hearing-aid use.

Following a restricted lesion of the cochlea, which produces a "dead region" (DR), animal experiments have revealed an increase in the cortical representation of frequencies just below the edge frequency (f(e)) of the DR. This may result in improved difference limens for frequency (DLFs) just below f(e). In previous studies to assess this, the value of f(e) was not determined precisely. We measured DLFs using human subjects with DRs for whom the values of f(e) had been determined precisely using psychophysical tuning curves. To prevent use of loudness cues, stimuli for the measurement of DLFs had a mean level falling along an equal-loudness contour and levels were roved over a 12-dB range. DLFs were measured for thirteen subjects with a DR in at least one ear. Almost all subjects with bilateral hearing loss exhibited enhanced DLFs near f(e), consistent with cortical reorganisation. This occurred for subjects whose audiograms had both steep and shallow slopes, regardless of hearing aid use, and for two subjects with low-frequency DRs. One subject with a high-frequency DR in one ear and good hearing in the other ear showed an enhanced DLF in her better ear.

Acoustic Stimulation↗
PubMed1993

N200 component of event-related potentials in depression.

Event-related potentials (ERPs) recorded during a two-tone discrimination (oddball) task were examined in 36 drug-free depressed patients and 36 control subjects. At remission, the ERPs of 12 of the depressed patients were reexamined. In the depressed patients, although a group difference was not detected in the peak latency and amplitude of N200 to rare stimuli, the mean amplitude for the N200 latency range in the difference waves was smaller than in the control subjects. Mismatch negativity (N2a), which was elicited by rare stimuli, was reduced in amplitude; but N2b may have been evoked to frequent stimuli more in the patients than in the control subjects. Depressed subjects may have a deviance in the fully automatic cerebral mismatch process that is assumed to be related to mismatch negativity and provoke the controlled mismatch detection process (presumed to be associated with N2b) even to nontarget frequent stimuli. These findings were observed during remission; however, there was a tendency for the N2b amplitude to decrease and recover toward the level of the control subjects.

Adolescent↗
PubMed2005

Event-related potentials in panic disorder and generalized anxiety disorder.

To evaluate the neurophysiological differences between panic disorder (PD) and generalized anxiety disorder (GAD), 52 patients with PD and 34 with GAD were investigated using event-related potentials (ERP). The ERP were recorded using a tone discrimination task, and peak latencies for N1, P2, N2, and P3 at a Pz electrode site were measured. In addition to analyzing the peak latencies of the ERP, the interpeak latencies (IPL; N1-P2, P2-N2, and N2-P3) were also analyzed. The same analysis was performed in 28 age-matched healthy volunteers (controls). When compared to those of the GAD and control groups, the mean latencies of P2, N2, and P3 were shorter in the PD patients. With regard to the IPL in the PD patients, the N1-P2 IPL was shorter than that in the other groups, and no individual with PD had a longer N1-P2 IPL than 1 SD above the mean of the controls. These findings suggest that certain attention-related processes in the cerebrum that affect ERP data are accelerated in PD patients. These findings demonstrate that it may be useful to neurophysiologically distinguish PD from GAD by measuring ERP peak latencies and IPL.

Adolescent↗
PubMed1991

Informational masking and auditory attention.

Informational masking is broadly defined as a degradation of auditory detection or discrimination of a signal embedded in a context of other similar sounds; it is not related to energetic masking caused by physical interactions between signal and masker. In this paper, we report a systematic release from informational masking of a target tone in a nine-tone rapid auditory sequence as the target is increasingly isolated in frequency or intensity from the remaining sequence components. Improved target-tone frequency difference limens as isolation increases are interpreted as a reflection of increasingly focused auditory attention. The change from diffuse to highly focused attention is gradual over the frequency and intensity ranges examined, with each 1-dB increment in target intensity relative to the remaining components producing performance improvements equivalent to those produced by a 2% increase in frequency isolation. The results are modeled as bands of attention in the frequency and intensity domains. For attention directed by frequency isolation, there is a strong correspondence with auditory filters predicted by the power spectrum model of masking. These data also support the existence of an attention band of intensity, with a bandwidth of about 5-7 dB at the moderate levels used in this experiment.

Adult↗
PubMed1989

Psychological intervention can partly alter P300-amplitude abnormalities in schizophrenics.

In the present study, we investigated whether psychological interventions can alter P300-abnormalities, specifically enhancing reduced P300-amplitudes, in schizophrenics. A three-tone discrimination task was employed for recording P300s, in which psychological intervention to facilitate target detection was performed through delivering a buzzer sound one second after each designated target tone that informed its occurrence. This procedure was done exclusively during the third and fourth sessions among the six sessions in total. When the data for all the patients were analyzed as a whole, no significant change was observed. However, when the patients were broken down into two groups based on the P300-amplitudes in the first and second sessions, significant effects of the intervention emerged. The group with smaller P300-amplitudes showed a significant increase in P300-amplitudes as well as improved performance levels during and after the intervention sessions. On the contrary, the group with larger P300-amplitudes displayed a significant decrease in P300-amplitudes in these sessions. Interestingly, the above results were consistent with the subjective difficulty changes experienced by the patients through the sessions. Overall, the above results indicate that psychological interventions can partly enhance reduced P300-amplitudes in schizophrenics.

Adult↗
PubMed2006

Frequency discrimination of complex tones by hearing-impaired subjects: Evidence for loss of ability to use temporal fine structure.

For normally hearing subjects, thresholds for discriminating the fundamental frequency (F0) of a complex tone, F0DLs, increase when the number of the lowest harmonic, N, is above eight. A previous study showed that F0DLs were affected by component phase for N above 7, and it was argued that the increase in F0DLs with increasing N reflects a loss of temporal fine structure information. Here, subjects with moderate hearing loss were tested in a similar experiment. F0DLs were measured for tones with three successive harmonics, added in cosine or alternating phase. The center frequency was 2000 Hz. N was varied by changing the mean F0. A background noise was used to mask combination tones. F0 was roved across trials and N was roved by +/-1, to reduce use of excitation pattern cues. F0DLs were smaller for cosine than for alternating phase for four out of six subjects, and this occurred once N exceeded 5. In contrast to the result for normally hearing subjects, F0DLs decreased with increasing N. Performance was much worse than obtained for normally hearing subjects at the same center frequency, suggesting that most of the hearing-impaired subjects had a poor ability to use temporal fine structure information.

Acoustic Stimulation↗
PubMed1998

The psychological refractory period: evidence for age differences in attentional time-sharing.

The authors report 2 psychological refractory period (PRP) experiments in which the stimulus onset asynchrony (SOA) between Task 1 and Task 2 was 150 ms, 250 ms, 600 ms, and 1,100 ms for both younger and older adults. H. Pashler's (1994a) response-selection bottleneck theory predicts that SOA manipulations should not affect Task 1 performance, but that reaction time (RT) for Task 2 should increase as the SOA between the 2 tasks decreases (i.e., the classical PRP effect). In Experiment 1 (Task 1 = tone discrimination, Task 2 = dot location), older adults showed a larger PRP effect than younger adults did, although Task 1 RT was affected by SOA, suggesting that participants were grouping their responses on some trials. That is, participants were holding their response for Task 1 until they had completed processing Task 2, and then they responded to both tasks almost simultaneously. However, a subset of participants (11 younger adults and 11 older adults) who showed no evidence of response grouping on Task 1 continued to show a larger PRP effect for older adults on Task 2. In Experiment 2 (Task 1 = dot location, Task 2 = simultaneous letter matching), older adults continued to show a larger PRP effect than younger adults for Task 2, and Task 1 performance was unaffected by SOA. Consequently, these experiments provide evidence that older adults (relative to younger adults) exhibit a decrement in time-sharing at the response-selection stage of processing. These results suggest that attentional time-sharing needs to be added to the list of topics examined in aging research on varieties of attention.

Adult↗
PubMed1991

Frequency discrimination as a function of signal frequency and level in normal-hearing and hearing-impaired listeners.

Frequency difference limens (DLFs) for pure tones were obtained over a wide range of frequencies and levels from 7 normal-hearing subjects and 16 ears of 12 listeners with sensorineural hearing losses. The normal data were fitted with a general prediction equation. Variability of the data around the DLFs estimated by the equation was quantified and used to evaluate the DLFs from the hearing-impaired listeners. The majority of DLFs from impaired listeners were poorer than one standard deviation above the estimates of the normal equation at all frequencies and sensation levels (SLs). The portion of the equation concerned with sensation level was fitted to each listener's data at each frequency. The slopes of these functions indicated that, on average, the rate of improvement of the DLF with sensation level was similar in the two groups of subjects. These results suggest that it would be reasonable to compare DLFs from normal-hearing and hearing-impaired listeners at equivalent sensation levels. The intercepts of the DLF-intensity functions represent asymptotic values obtained at high SLs. These asymptotic DLFs were abnormal in the majority of hearing-impaired subjects, with more than half the data in excess of two standard deviations above normal. However, among those subjects, the correlation between the DLF deficit and the amount of hearing loss at the test frequency was not strong (r = +.27).

Acoustics↗
PubMed1997

Detection of silent intervals between noises activating different perceptual channels: some properties of "central" auditory gap detection.

This article describes four experiments on gap detection by normal listeners, with the general goal being to examine the consequences of using noises in different perceptual channels to delimit a silent temporal gap to be detected. In experiment 1, subjects were presented with pairs of narrow-band noise sequences. The leading element in each pair had a center frequency of 2 kHz and the trailing element's center frequency was parametrically varied. Gap detection thresholds became increasingly poor, sometimes by up to an order of magnitude, as the spectral disparity was increased between the noise bursts that marked the gap. These data suggested that gap-detection performance is impoverished when the underlying perceptual timing operation requires a comparison of activity in different perceptual channels rather than a discontinuity detection within a given channel. In experiment 2, we assessed the effect of leading-element duration in within-channel and between-channel gap detection tasks. Gap detection thresholds rose when the duration of the leading element was less than about 30 ms, but only in the between-channel case. In experiment 3, the gap-detection stimulus was redesigned so that we could probe the perceptual mechanisms that might be involved in stop consonant discrimination. The leading element was a wideband noise burst, and the trailing element was a 300-ms bandpassed noise centered on 1.0 kHz. The independent variable was the duration of the leading element, and the dependent variable was the smallest detectable gap between the elements. When the leading element was short in duration (5-10 ms), gap thresholds were close to 30 ms, which is close to the voice onset time that parses some voiced from unvoiced stop consonants. In experiment 4, the generality of the leading-element duration effect in between-channel gap detection was examined. Spectrally identical noises defining the leading and trailing edges of the gap were presented to the same or to different ears. There was a leading-element duration effect only for the between channel case. The mean gap threshold was again close to 30 ms for short leading-element durations. Taken together, the data suggest that gap detection requiring a temporal correlation of activity in different perceptual channels is a fundamentally different task to the discontinuity detection used to execute gap detection performance in the traditional, within-channel paradigm.

Adult↗
PubMed1992

Spectral and temporal weights in spectral-shape discrimination.

The COSS analysis [B. G. Berg, J. Acoust. Soc. Am. 86, 1743-1746 (1989)] was used to estimate spectral and temporal weights of a three-component, amplitude-modulated stimulus in a spectral-shape discrimination task. In all experiments, the task of the observer was to detect an increment in the level of the center component. A spectral-temporal weight quantifies the relative influence of a spectral component on the decisions of an observer during a specified segment of the total stimulus duration. In the first two experiments, the signal was added to all three temporal segments of the center component. The ideal weights for each component should be the same across temporal segments. Spectral-temporal weights were obtained for four conditions with different stimulus durations. In general, the estimated weights for each component were not equal at different temporal segments. In the third experiment, the signal was added to only one of three segments of the center component. Ideally, weight patterns should have changed when the temporal position of the signal segment was altered. Two stimulus durations, 300 and 15 ms, were used. For the 300-ms condition, the signal was added to only the end segment, and for all three observers the weight patterns are different from that obtained in experiment 1 with the signal added to all segments. For the 15-ms conditions, altering the signal position changed the estimated weights for only one observer.

Adult↗
PubMed1994

Formant-frequency discrimination for isolated English vowels.

Thresholds for formant-frequency discrimination were obtained for ten synthetic English vowels patterned after a female talker. To estimate the resolution of the auditory system for these stimuli, thresholds were measured using well-trained subjects under minimal-stimulus-uncertainty procedures. Thresholds were estimated for both increments and decrements in formant frequency for the first and second formants. Reliable measurements of threshold were obtained for most formants tested, the exceptions occurring when a harmonic of the fundamental was aligned with the center frequency of the test formant. In these cases, unusually high thresholds were obtained from some subjects and asymmetrical thresholds were measured for increments versus decrements in formant frequency. Excluding those cases, thresholds for formant frequency, delta F, are best described as a piecewise-linear function of frequency which is constant at about 14 Hz in the F1 frequency region (< 800 Hz), and increases linearly in the F2 region. In the F2 region, the resolution for formant frequency is approximately 1.5%. The present thresholds are similar to previous estimates in the F1 region, but about a factor of three lower than those in the F2 region. Comparisons of these results to those for pure tones and for complex, nonspeech stimuli are discussed.

Adult↗
PubMedDate not supplied

Intensity and frequency discrimination monitored by evoked response audiometry: clinical application.

Delta 1 and delta f repetitive stimuli superimposed on continuous 0.5-, 1- and 4-kHz carrier tones were administered to 20 normally hearing persons, 8 adults with sensorineural hearing loss, 10 adults with conductive hearing loss and 22 children subjected to evoked response audiometry (ERA) for assessment of hearing acuity. The intensity modulation depth ranged from + 1 to 10 dB. In the subjects with normal hearing and in the adult patients, three carrier tone levels were used whenever possible: 20, 40, and 60 dB SL. The frequency modulation depth ranged from -1 to -10% of the carrier tone frequency. The same levels for the carrier tone were used: 20, 40, and 60 dB SL. With a carrier tone level of 20 dB SL, a clear-cut vertex response was noted in 80% of the tests carried out in the normal adults with 5-dB delta i stimuli and with delta f stimuli of -3 to -5% in magnitude; the same figures are valid for the patients with sensorineural and conductive hearing loss. The patients with sensorineural hearing loss showed a tendency to give vertex responses with lower delta i stimuli than subjects with normal hearing. However, this difference was not statistically significant. According to our results, the children tested can be roughly divided into two groups, the first including subjects with responses to delta i stimuli of +5 and +10 dB and delta f stimuli of -5% and -10%; the second group including subjects with no clear-cut responses to these stimuli.

Acoustic Stimulation↗
PubMed2004

Auditory lexical decision, categorical perception, and FM direction discrimination differentially engage left and right auditory cortex.

Recent neuroimaging and neuropsychological data suggest that speech perception is supported in bilaterally auditory areas. We evaluate this issue building on well-known behavioral effects. While undergoing positron emission tomography (PET), subjects performed standard auditory tasks: direction discrimination of frequency-modulated (FM) tones, categorical perception (CP) of consonant-vowel (CV) syllables, and word/non-word judgments (lexical decision, LD). Compared to rest, the three conditions led to bilateral activation of the auditory cortices. However, lateralization patterns differed as a function of stimulus type: the LD task generated stronger responses in the left, the FM task a stronger response in the right hemisphere. Contrasts between either words or syllables versus FM were associated with significantly greater activity bilaterally in superior temporal gyrus (STG) ventro-lateral to Heschl's gyrus. These activations extended into the superior temporal sulcus (STS) and the middle temporal gyrus (MTG) and were greater in the left. The same areas were more active in the LD than the CP task. In contrast, the FM task was associated with significantly greater activity in the right lateral-posterior STG and lateral MTG. The findings argue for a view in which speech perception is mediated bilaterally in the auditory cortices and that the well-documented lateralization is likely associated with processes subsequent to the auditory analysis of speech.

Acoustic Stimulation↗
PubMed1994

Altered attentional processing of background stimuli in Gilles de la Tourette syndrome: a study in auditory event-related potentials evoked in an oddball paradigm.

In 24 adults and 29 children both with Gilles de la Tourette syndrome and in 24 control adults and 17 control children we studied auditory event-related potentials (ERP's) evoked in 2 different oddball paradigms: a passive listening paradigm (PLP) in which subjects had only to attend tones (260 standards, 40 deviants), followed by an active discrimination paradigm (ADP) in which subjects had to press a microswitch in response to the deviant tones. In the adult Tourette patients the PLP disclosed between 200-300 msec at all derivations (Fz, Cz, Pz, C3, C4, P3, P4) a significantly more negative activity than in the controls. In the Tourette children such a result was only found at Fz. In the ADP the differences between both adult groups disappeared, but the curves of the control children became now significantly more positive than those of the Tourette ones except at C3 and P3. Between 200-300 msec the curves of all 4 groups were significantly less negative in the ADP than in the PLP. This decrease in negativity was significantly larger in the adult Tourette patients than in the adult controls, but in the children groups the reverse occurred. It is hypothesized that the differences in amplitude between patients and controls and between both paradigms are due to differences in amplitude of an endogenous negative component overlapping the exogenous N100-N200 standard curve. Based on this hypothesis the results could suggest that one of the problems in Tourette syndrome is an increased attention to non-relevant stimuli.

Adolescent↗
PubMed2006

Frequency discrimination of complex tones; assessing the role of component resolvability and temporal fine structure.

Thresholds for discriminating the fundamental frequency (FO) of a complex tone, FODLs, are small when low harmonics are present, but increase when the number of the lowest harmonic, N, is above eight. To assess whether the relatively small FODLs for N in the range 8-10 are based on (partly) resolved harmonics or on temporal fine structure information, FODLs were measured as a function of N for tones with three successive harmonics which were added either in cosine or alternating phase. The center frequency was 2000 Hz, and N was varied by changing the mean FO. A background noise was used to mask combination tones. The value of FO was roved across trials to force subjects to make within-trial comparisons. N was roved by +/- 1 for every stimulus, to prevent subjects from using excitation pattern cues. FODLs were not influenced by component phase for N= 6 or 7, but were smaller for cosine than for alternating phase once N exceeded 7, suggesting that temporal fine structure plays a role in this range. When the center frequency was increased to 5000 Hz, performance was much worse for low N, suggesting that phase locking is important for obtaining low FODLs with resolved harmonics.

Acoustic Stimulation↗