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PubMed1989

Effects of auditory masking on lingual vibrotactile magnitude-estimation scaling responses of young children.

Studies of lingual vibrotactile magnitude-estimation scaling have focused primarily on the responses of normal young adults. Little is known about the scaling responses of young children to suprathreshold vibratory stimulation because of the complexities of the experimental procedure. Binaural auditory masking is one aspect of the procedure that has recently been studied in adults. The purpose of this study was to investigate the effects of binaural auditory masking on lingual vibrotactile magnitude-estimation responses of young children. Four children whose mean age was 4.6 yr. completed magnitude-estimation scaling tasks for eight lingual vibrotactile suprathreshold intensity levels (6, 10, 16, 20, 26, 30, 36, 40 dB SL) under masking and no masking conditions. Results suggest possible effects of auditory masking on the lingual vibrotactile magnitude-estimation scaling responses of these young children that have not been found for such responses of adults.

Auditory Perception↗
PubMedDate not supplied

Influence of test tone duration on auditory masking patterns.

Temporal integration functions of tone bursts masked by critical band noises become shallower with increasing test tone frequency. This holds for tone bursts in the centre as well as at the slopes of the masking pattern of critical band maskers. When shortening the tone bursts, the horizontal masking pattern of uniform masking noise changes into a pattern with decreasing slope for increasing frequency. The shape of the masking pattern of critical band maskers remains rather independent of test tone duration.

Acoustic Stimulation↗
PubMed1982

Location-specific components of the gross cochlear action potential: an assessment of the validity of the high-pass masking technique by cochlear nerve fibre recording in the cat.

The auditory high-pass masking technique has been used in attempts to define the origin, along the cochlear partition, of the gross cochlear action potential (CAP) and the gross brain stem potential. Theoretically, the high-pass masking paradigm should be frequency and location specific at the cochlear level, and some indirect evidence does point to this specificity. However, this hypothesis has not yet been directly substantiated. In the present experiment, click-evoked cochlear nerve activity was recorded simultaneously from the round window and from single fibres of the cochlear nerve, with and without high-pass maskers spaced in octaves from 0.5 to 16 kHz, at three intensities, in the anaesthetized cat. The "derived' CAPs were computed and compared with the mapping of single cochlear fibre responses under the same conditions. With one main exception, the conclusions drawn on the origin of the frequency components of the "derived' potentials were found to be valid in the normal cat. The exception concerned fibres with characteristic frequencies below 1-2 kHz, where the substantial spread towards the high frequencies of their frequency threshold curves, and the effects of lateral suppression or of other "remote masking' phenomena rendered the high-pass masking less location specific. From these results and certain assumptions, we would predict the high-pass masking technique to be valid in electrophysiological investigations in normal humans for frequencies down to 0.5-1 kHz.

Animals↗
PubMed1985

Extra-high-frequency noise remotely masks and alters temporal integration at lower frequencies.

A quasi-free-field technique was used to assess the effects of extra-high-frequency-band masking on detection threshold of middle and high (1-7 kHz) frequencies. At an SPL of 60 dB, the 10- to 20-kHz masker produced a slight amount of masking. Increasing the masking level by another 5 dB produced a disproportionate increase of the detection thresholds. This increase was greatest in response to 4- and 5-kHz stimuli, and was detected with both constant and pulsed tones. Decreasing the bandwidth of the masker reduced the magnitude of the effect, but not the frequency-specific pattern of the remote masking. Extra-high-frequency masking also increased the amount of temporal integration at middle and high frequencies. The data are discussed in reference to peripheral and central neural changes associated with sensorineural hearing loss.

Adult↗
PubMed1989

Evoked-response forward-masking functions in chinchillas with noise-induced permanent hearing loss.

Evoked-response forward-masking functions were measured by chronic electrodes in the inferior colliculus of the chinchilla before and after exposure to an intense tone that produced a permanent hearing loss. Before exposure, the forward-masking time constants ranged from 50 to 90 ms. After exposure, the forward-masking time constants increased significantly in the region of hearing loss, but not in regions where hearing was normal. The effect of the hearing loss on the time course of forward masking was most pronounced once the hearing loss exceeded 20-25 dB. These physiological changes in the evoked-response forward-masking functions appear to parallel those observed psychophysically in human listeners.

Animals↗
PubMedDate not supplied

Frequency-specific brainstem responses to bone-conducted tone pulses masked by notched noise.

As in the case of auditory brainstem responses (ABRs) to air-conducted stimuli, recording of frequency-specific ABRs to bone-conducted stimuli needs adequate masking of those parts of the basilar membrane that are not to contribute to the ABR. The present study shows that tone-pulse stimulation with notched noise-masking can be realized via a bone vibrator after its frequency response has been flattened. The latency-intensity curves for 4, 2, 1, and 0.5 kHz run approximately parallel, indicating the ABR to be indeed frequency-specific. As adequate air-conducted masking of the nontest ear can produce cross-masking, the use of an insert earphone is proposed. Because of its higher interaural attenuation, a higher masking level can be applied to the nontest ear.

Bone Conduction↗
PubMed1985

Electrophysiological correlates of visual masking.

The phenomenon of paracontrast documented by means of psychophysical techniques has not been readily demonstrable using electrophysiological responses as an index of masking. We have analyzed averaged cortical potentials during presentation of visual stimuli that produce psychophysical masking. Differences in the masking profiles obtained from the two experimental conditions are apparent. However, both electrophysiological and psychophysical data do indicate an interaction between responses to an annulus and a disc which varies with the time interval between the stimuli. Both sets of data also reflect differences in masking between right and left eyes. We conclude that the cortical potentials evoked by temporally disparate stimuli do interact, but that the masking profile is not identical to the profile obtained by psychophysical methods.

Adult↗
PubMed1981

Critical masking bands for sensorineural tinnitus.

The level of noise required to mask tinnitus was measured in 12 subjects with sensorineural tinnitus; the noise was centred on the estimated pitch of the tinnitus, and the overall level required to just mask the tinnitus was measured for masker bandwidths of 2.5, 10, 20, 30 and 50% of the noise centre-frequency. For four of the tinnitus subjects, masking functions were similar to those observed in normal-hearing subjects with a "simulated" tinnitus (15-dB Sensation Level, 4-kHz pure tone). The other eight tinnitus subjects, however, required masking levels that were either independent of masker bandwidth or showed anomalous changes in masker level as bandwidth was increased. These results suggest that certain masker bandwidths can be more efficient than others for the masking of tinnitus, and that masker characteristics deserve close attention in the design and fitting of tinnitus-masker instruments.

Acoustics↗
PubMed1992

High-frequency audiometry. Masking of air- and bone-conduction signals.

Interaural attenuation has been investigated for both air-conduction and bone-conduction signals in the frequency ranges 0.25-18 and 0.25-16 kHz respectively. Ear canal occlusion is recommended when using the Koss HV/1A earphone for BC masking, as acoustic transmission occurs through the headset in the high-frequency range. Minimum masking levels for 1/3-octave filtered white noise were established for bone-conduction signals in the frequency range 8-16 kHz. Central masking of bone-conduction signals proved to be of the same order of magnitude in the conventional- and high-frequency ranges, while the cross-masking level was approximately 10-15 dB lower above 6 kHz. Recommendations are made for a masking procedure in the high frequency range.

Acoustic Stimulation↗
PubMed1995

Effect of contralateral white noise masking on the mismatch negativity.

Mismatch negativity (MMN), an auditive event-related potential (ERP) component, evoked by deviant stimuli in a homogeneous stream of standard stimuli was studied in a unilateral stimulation and contralateral white noise masking condition. Eleven subjects (Ss) with normal hearing (aged 20-35 years) were examined using sine tone stimuli (70 dB HL, interstimulus interval 300 ms, duration 40 ms with 5 ms rise and fall times). Three blocks of standard (std)/deviant (dev) series of stimuli were used: std 500/dev 600 Hz, std 2000/dev 1900 Hz, and std 2000/dev 1600 Hz. The first block was repeated for another group of 11 Ss with normal hearing (aged 17-27 years). The MMN was analysed from the difference curves recorded at Fz, Cz and Pz. The stimuli were delivered unilaterally, either with or without 50 dB effective masking level white noise to the contralateral ear. The MMN amplitude attenuated significantly when contralateral masking was used. In addition, there was interaction between noise masking and the stimulated ear. The MMN latencies were not affected by white noise masking.

Adult↗
PubMed1982

Normal variation in the masking effectiveness of the narrow band noises of one audiometer.

The minimum effective masking levels (MEMLs) of the narrow band masking noises (audiometric frequencies 0.25-4 kHz) of one audiometer were determined for a sample of 40 normal individuals. The variation in MEML was rather wide but it decreased with increasing frequency. After consideration of the plateau procedure for masking, it is recommended that the starting level of masking should be: Threshold of masking+mean MEML+10 dB. This should be sufficient to prevent finding false plateaux and hence obviate the possibility of obtaining a threshold for the test ear which in fact relates to the non-test ear.

Adult↗
PubMed2003

Priming of mental operations by masked stimuli.

Motor responses can be affected by visual stimuli that have been made invisible by masking. Can masked visual stimuli also affect nonmotor operations that are necessary to perform the task? Here, I report priming effects of masked stimuli on operations that were cued by masking stimuli. Cues informed participants about operations that had to be executed with a forthcoming target stimulus. In five experiments, cues indicated (1) the required response, (2) part of the motor response, (3) the stimulus modality of the target stimulus, or (4) the task to be performed on a multidimensional stimulus. Motor and nonmotor priming effects followed comparable time courses, which differed from those of prime recognition. Experiment 5 demonstrated nonmotor priming without prime awareness. Results suggest that motor and nonmotor operations are similarly affected by masked stimuli.

Adult↗
PubMed2004

Mask-dependent attentional cuing effects in visual signal detection: the psychometric function for contrast.

A spatial-cuing paradigm was used to test the hypothesis of Carrasco, Penpeci-Talgar, and Eckstein (2000) that the mask-dependent cuing effects found in visual signal detection by Smith (2000a) were caused by submaximal activation of the transient-orienting system. Mask-dependent cuing was found with a range of stimulus contrasts with pure peripheral cues and with the mixed central-peripheral cues of Smith (2000a), contrary to the predictions of the submaximal activation hypothesis. The use of a pedestal detection task to control spatial uncertainty showed that the cuing effect was due to signal enhancement. A model of mask-dependent cuing is described, which assumes that attention affects the rate of information accumulation from the display and that masks limit the visual persistence of the stimulus. The model correctly predicts differential mask dependencies in sensitivity for detection and discrimination and the associated patterns of response times.

Adolescent↗
PubMed2002

The masked onset priming effect in naming: computation of phonology or speech planning?

We investigated factors that modulate the presence of the masked onset priming effect in three naming experiments. In Experiment 1, we showed that the masked onset priming effect is found with regular words, but not with exception words, replicating the finding reported by Forster and Davis (1991). In Experiment 2, we used the conditional naming task in which words are mixed with nonwords and participants are instructed to name the item only if it is a word. The masked onset priming effect was eliminated in this experiment, but the regularity effect remained. In Experiment 3, regular and irregular words were mixed randomly, rather than in separate blocks as in Experiment 1. This reduced the size of the regularity effect, and the masked onset priming effect was again absent. We argue that these results, taken as a whole, are better interpreted within the view that the masked onset priming effect has its origin in the preparation of a speech response, rather than within the original dual-route interpretation proposed by Forster and Davis.

Electronic Data Processing↗
PubMed2000

Recent models and findings in visual backward masking: a comparison, review, and update.

Visual backward masking not only is an empirically rich and theoretically interesting phenomenon but also has found increasing application as a powerful methodological tool in studies of visual information processing and as a useful instrument for investigating visual function in a variety of specific subject populations. Since the dual-channel, sustained-transient approach to visual masking was introduced about two decades ago, several new models of backward masking and metacontrast have been proposed as alternative approaches to visual masking. In this article, we outline, review, and evaluate three such approaches: an extension of the dual-channel approach as realized in the neural network model of retino-cortical dynamics (Ogmen, 1993), the perceptual retouch theory (Bachmann, 1984, 1994), and the boundary contour system (Francis, 1997; Grossberg & Mingolla, 1985b). Recent psychophysical and electrophysiological findings relevant to backward masking are reviewed and, whenever possible, are related to the aforementioned models. Besides noting the positive aspects of these models, we also list their problems and suggest changes that may improve them and experiments that can empirically test them.

Animals↗
PubMed2005

Human frequency-following responses to binaural masking level difference stimuli.

Binaural masking level difference is the behavioral threshold difference between a diotic condition (SoNo) and a dichotic condition with a 180 degrees interaural phase delay of either the signal (SpiNo) or the masker (SoNpi). Threshold disparity is partially related to coincidence-detecting units in the medial superior olive that are sensitive to low-frequency binaural stimuli with interaural phase differences. Previous surface evoked potential studies report significant latency and amplitude differences to SpiNo stimuli with respect to SoNo stimuli in the P1-N1 auditory event related potential, but no study has reported physiologic masking level differences in a brain stem evoked potential. The human frequency-following response (FFR) represents activity from low-frequency, phase locking neural units in the upper brainstem. Unmasked FFRs to 500 Hz tone bursts and masked FFRs using a 1.5 kHz low-pass masker were recorded from nine normal-hearing adult subjects. Significant reduction in FFR amplitude occurred in the SoNo condition, re the So condition, with masker intensities near the psychoacoustic SoNo masking level. Significant FFR amplitude recovery was observed for both the SoNpi and SpiNo conditions. These results support the role of phase-locked neural activity in brainstem mechanisms involved in perceptual masking release.

Adolescent↗
PubMed1990

[The influence of face masks and a nasal nozzle on nasal airflow].

In an attempt to detect the influence of various kinds of face masks and a nasal nozzle on nasal airflow, we made measurements of nasal resistance by a head-out body plethysmograph with or without the masks on the face or the nozzle to the nostril of the normal adult subjects. The mean values of nasal resistance with the masks differed from the mean values without the masks significantly. No significant difference between values with and without the nozzle was found. The coefficient variations of 40 consecutive measurements of nasal resistance with the masks or the nozzle had wider ranges than those without the apparatuses. But the variation due to the nozzle was the minimum in the apparatuses.

Adult↗
PubMedDate not supplied

Mechanical airway obstruction from the laryngeal mask airway cuff.

BACKGROUND: The laryngeal mask airway (LMA) classic has been found useful in airway management of both routine and emergency unexpected failed intubations. We report a case of mechanical airway obstruction from anterior in folding of the laryngeal mask airway classical cuff. METHOD: The anaesthetic record of a 55-year-old 70 kg female patient fora left sided total hip replacement that had a failed spinal and was augmented with the laryngeal mask airway. RESULT: Near complete airway obstruction developed after the size 4 laryngeal mask airway classic was inserted and the cuff inflated with 30 ml of air. The reduced reservoir volume and the desaturation that ensued as detected by the portable handheld pulse oximeter alerted the anesthesiologist and called for a check which was not corrected by any head and neck manoeuvre. On withdrawal of the laryngeal mask airway, the cuff was noted to have folded unto the fresh gas aperture thereby obstructing ventilation and oxygenation of the patient. CONCLUSION: Monitoring the monitors and quick reassessment of laryngeal cuff placement guaranties the evasion of anaesethetic catastrophes.

Airway Obstruction↗