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PubMed2005

[Distribution effects of orthographic similarity and priming by masked repetition].

This research centres on the effect that the orthographic neighbourhood has in the visual recognition of words. Specifically, we studied to what extent orthographic neighbourhood distribution, that is, the number of letter positions allowing formation of at least one neighbour (Pugh, Rexer, Peter, & Katz, 1994), influences the masked repetition priming effect. In a previous study (Mathey, Robert, & Zagar, 2004), interaction between neighbourhood distribution and orthographic priming was obtained in the lexical decision task. The Interactive Activation Model (IA; McClelland & Rumelhart, 1981) simulated this interaction. With the orthographic priming effect modified for distribution of the neighbourhood of target words, it was necessary to study whether the repetition priming effect also varied as a function of this indicator. Studying this interaction presents a major theoretical issue in specifying the activating and inhibiting processes presented in the IA model. Simulations were produced to obtain precise model predictions regarding the neighbourhood distribution effect in a repetitive priming situation for our experimental material. Target words all had two neighbours that were most frequent. These neighbours were isolated, that is, distributed over two letter positions (e.g.: TAUX/faux-toux), or associated, i.e., concentrated on one single position (e.g., SEAU/beau-peau). Targets were preceded by an identical priming (repetitive priming; e.g.: seau-SEAU) or by controlled priming (e.g., &&&&-SEAU). The simulation results obtained using the IA model show the facilitating effects of neighbourhood distribution and repetitive priming, but no interaction between these factors. The experimental results obtained in a lexical decision task confirm these predictions. Thus, the empirical data replicate the neighbourhood distribution's facilitating effect (Mathey & Zagar, 2000) as well as the facilitating effect of masked repetition (Forster & Davis, 1984). Finally, the most interesting result is that the facilitating effect of repetition is comparable for target words with associated neighbours and target words with isolated neighbours. An explanation of the combined effects of the orthographic neighbourhood and orthographic masked repetition priming, integrating data from literature as well as from the current study, is proposed within the framework of the IA model.

Humans↗
PubMed1990

The Brain laryngeal mask. An alternative to difficult intubation.

We report the case of a young man undergoing fixation of bilateral mandibular fractures, where the anaesthetist was unable to intubate. A Brain laryngeal mask was employed, thus enabling surgery to proceed. This relatively new device enabled the airway to be safeguarded whilst preserving reasonable surgical access for the attachment of Erich arch bars and a four hole osteosynthetic bone plate. The surgical and anaesthetic procedures are summarised. The laryngeal mask is described and its performance and limitations are discussed. We believe this to be the first report of mandibular fracture fixation performed with a Brain laryngeal mask in situ.

Adult↗
PubMed2002

A comparison of the effects of broadband masking noise on the auditory brainstem response in young and older adults.

We examined the effects of ipsilateral-direct, continuous, broadband noise on auditory brainstem response (ABR) wave I and V latencies and amplitudes in young adult versus older adult humans. It was hypothesized that age might influence the effects of masking noise on ABR peak latencies and/or amplitudes, given the frequent complaint of older persons' ability to process speech in background noise. Young adults had hearing thresholds of 20 dB HL or better for the octave frequencies from 250 to 8,000 Hz. A subset of older study participants had thresholds of 20 dB HL or better across frequency, but others had thresholds up to 45 dB HL. All data were collected and analyzed with a Nicolet Bravo. An electrode was placed on the tympanic membrane (as well as on high forehead and contralateral mastoid), and a click level of 115 dB pSPL was used to maximize wave I amplitude. Masker conditions included a no-noise control and noise levels ranging from 20 to 70 dB effective masking, in 10 dB steps. With increasing noise level, both age groups showed minimal changes in wave I latency, but substantial increases in wave V latency and I-V interval. Peak amplitudes decreased with increasing noise level. Mean amplitudes were smaller for the older group, most notably for wave I. Mean peak latencies were greater in the older group, but the I-V interval was similar across age groups, as was the change in peak latencies and I-V interval across noise level. ABR parameters for the older adults with hearing meeting the 20-dB HL criterion at all frequencies (older-better) were compared to those who didn't meet this criterion (older-worse). Mean wave I latency was greater and wave V latency and I-V interval were smaller for the older-worse group at all noise levels. Mean wave I and V amplitudes were similar for the older-better and older-worse groups. In participants with normal or near-normal hearing, ABR changes with increasing age included small latency increases and a substantial reduction in wave I amplitude. The effects of ipsilateral-direct masking noise on the click-evoked ABR are similar for young and older adults.

Adult↗
PubMed1975

Intelligibility characteristics of superior esophageal speech presented under various levels of masking noise.

Broad-band masking of speech was used to assess the effects that broad-band masking noise had upon the recognition of consonants and vowels produced by esophageal speakers. Procedures were developed to compare the articulation functions of superior esophageal speech with those of normal speech under comparable levels of masking noise. Within the range of speech-to-noise ratios studied, articulation functions for vowels were essentially the same for esophageal and normal talkers (4% per dB). With respect to consonants, the intelligibility scores for esophageal speech were 12 to 14% lower than for normal speech under adverse noise conditions. Gains in the consonant articulation functions were 2.5%/dB and 4%/dB for normal and esophageal talkers, respectively. For adverse noise conditions, the lowered consonant scores for esophageal speakers were the result of poorer than normal intelligibility for liquid-glides and nasal and, secondarily, for stop consonants. Additional differences between the intelligibility characteristics of esophageal and normal speech were found in work-position and voicing features.

Adult↗
PubMed1975

The measurement of critical masking bands.

The characteristics of the critical masking band, that spectral region of a wideband noise that is effective in masking a pure-tone signal, were inferred by measuring detectability (d) for tonal signals as a function of the cutoff frequency of a low-pass or high-pass noise masker. As the cutoff frequency of a low-pass noise was decreased from the wide-band (100-7000 Hz) condition toward the signal frequency, (500, 1000, or 4000 Hz) dectability maintained a constant minimum until a further reduction in cutoff frequency increased detectability, presumably due to a reduction in masker power within the critical band. As cutoff frequency was reduced further, detectability increased monotonically until detection reached 100%. This usually occurred when the cutoff frequency is 0.04 to 0.06 octaves below the signal frequency. The range of cutoff frequencies over which detectability changes occurred defines the critical masking band. These ranges correspond closely to well-known critical ratio data. The dependence of d on noise cutoff frequency did not differ at the two signal levels (15 and 25 dB SL) used in this experiment. The critical band appeared symmetrical about the signal frequency for most subjects and most experimental conditions, although some subjects displayed a marked asymmetry in the high frequency direction for some conditions.

Acoustic Stimulation↗
PubMed1977

Effects of auditory masking on lip movements during speech.

This study describes the effects of unpredictably presented masking noise on selected parameters of lip movement during speech. Four normal subjects produced a simple speech utterance while vertical displacements of the upper and lower lips were transduced and recorded. During selected productions a masking noise was presented dichotically at one of two distinct phases of lip movement. Analysis of the resulting data revealed the following for all subjects: (1) significant changes in the duration, displacement, and velocity of lip movement caused by masking and (2) significant reductions in the velocity of lip movement occurring approximately 50 msec after the onset of the masker. Possible explanations of these and certain speaker-dependent effects are discussed.

Acoustic Stimulation↗
PubMed1981

Masking of noise bursts by an adjacent vowel for hearing-impaired listeners.

Some masking effects of synthetic vowels on adjacent noise bursts are reported for hearing-impaired listeners. The 200-ms vowels were similar to [a] and [i]; the 50-ms noise bursts were in one of three frequency bands: .5 to 1.5, 1.5 to 4, or 4 to 6 kHz. With voiceless-stop-like temporal intervals between the stimuli, there was little backward or forward masking of the noise bursts by either vowel. Some forward masking occurred under proximate conditions of vowel and burst in time and frequency.

Auditory Threshold↗
PubMed1984

Masking-level difference in filtered-random and amplitude-modulated noise.

The masking characteristics of filtered-random noise and amplitude-modulated noise (40-dB pressure-spectrum level) were studied in a series of four experiments using a masking-level difference paradigm, that is, 500-Hz thresholds in S0N0 and SpiN0 binaural conditions. In Experiment 1 a filtered noise (200-800 Hz) and an amplitude-modulated noise (425-575 Hz) produced equal thresholds in S0N0; for SpiN0, however, the thresholds in amplitude-modulated noise were 1.6 dB lower than were the thresholds in filtered noise. In Experiment 2 S0N0 and SpiN0 thresholds were established in three filtered noise bandwidths (200-800 Hz, 335-685 Hz, and 410-600 Hz) and in the amplitude-modulated noise (425-575 Hz). When the bandwidths of the filtered-random and amplitude-modulated noises were similar, the SpiN0 thresholds were the same but the S0N0 thresholds were different. Experiments 3 and 4 indicated that with amplitude-modulated noise when the zero amplitude crossings of the tone and the noise coincided, the S0N0, SpiN0, and SmNm thresholds were 1.2-2.0 dB higher than were the thresholds when the zero crossings of the tone and noise did not coincide. The data indicate that the masking characteristics of filtered-random noise and amplitude-modulated noise are different. The findings are interpreted as an indication that perceptual phenomena depend on the temporal characteristics as well as the power spectrum of the signal and masker.

Adult↗
PubMed1986

Masked and filtered simulation of hearing loss: effects on consonant recognition.

Hearing threshold configuration of the impaired ear was simulated via two different methods in the normal ear of each of 6 subjects with unilateral sensorineural hearing loss. The two hearing loss simulation methods were frequency-specific attenuation (filtering), and masking by shaped masking noise. Identification responses to 20 consonant-vowel nonsense syllables were obtained from the normal ear of each subject in the two hearing loss simulation conditions, as well as from the impaired ear. Speech data were scored both for overall percent correct consonant recognition and for error patterns on a set of eight consonant features. The computed correlation between gross error difference scores and a similarity metric for feature error pattern was essentially zero, indicating that these may be relatively independent measures of speech recognition, and thus may reflect different aspects of subjects' behavior. For 3 subjects, both masking and filtering successfully simulated the effects of sensorineural hearing loss on consonant feature error patterns. For 1 subject, only filtering produced feature error patterns similar to those of the impaired ear. For the remaining subjects, neither simulation was successful.

Adult↗
PubMed1988

Binaural release from masking for a speech sound in infants, preschoolers, and adults.

Binaural masked thresholds for a speech sound [ba] were estimated under two interaural phase conditions (NoSo and NoS pi) in three age groups (infants, preschool children, and adults). A computer-based head-turn with visual reinforcement procedure was used to test the infants. Preschoolers were tested using a modified play audiometry task, and adults were tested conventionally with the same apparatus as used with the infants. Differences in masked threshold as a function of both age and interaural phase condition, and differences in the binaural masking level difference (BMLD) with age, were found when the masker intensity was the same for each group. However, testing of adults with maskers of reduced intensity to compensate for hearing threshold differences relative to the two younger groups (a possible confounding variable in the estimate of the BMLD) eliminated the difference in BMLD between adults and preschoolers. The difference between infants and adults remained statistically significant, suggesting a possible developmental change in binaural hearing early in life. The relevance of developmental change in binaural hearing with respect to both infant auditory processing and the methods we use to assess it are discussed.

Adult↗
PubMed1989

Adaptation and the masking of tinnitus.

The effect of adaptation on the masking of tinnitus was investigated. Six patients with tinnitus performed two 5-min tracking tasks, each replicated six times. The first task examined the masking of tinnitus by tracking the intensity of a pure tone required to mask the tinnitus. The second task examined adaptation of a suprathreshold tone by tracking the intensity of a pure tone required for constant loudness. For 3 patients, the change required for constant loudness did not differ from the change required for constant maskability. For 3 patients, however, these two changes were different. Possible implications of these results for determining the locus of tinnitus and for the use of tinnitus maskers are discussed.

Adaptation, Physiological↗
PubMed1992

Masking of tinnitus induced by sound.

Two experiments were performed in which 8 listeners used external sound to mask the tinnitus induced by a 95-dB SPL tone presented for 1 min. Wider bandwidth noises were more effective maskers than noises of critical bandwidth, which, in turn, were more effective than tonal maskers. Contralateral maskers were often effective, but less so than ipsilateral maskers. Tuning curves showed some degree of frequency specificity that was not related to the frequency of the tinnitus-inducing tone. There were consistent and pronounced differences between individual listeners. Overall, our results indicate both similarities and differences between the masking of induced tinnitus and the masking of pathological tinnitus.

Adult↗
PubMed2003

Dissociations among attention, perception, and awareness during object-substitution masking.

When a visual target object is surrounded by four dots that onset at the same time as the target but remain visible after the target terminates, the four dots dramatically impair target discrimination performance. This phenomenon is called object-substitution masking, reflecting the hypothesis that both the target and the four dots are identified, but the representation of the four dots replaces the representation of the target object before the target can be reported. The present study used the event-related potential technique to demonstrate that a target masked in this manner is identified by the visual system and triggers a shift of attention. However, by the time attention is shifted to the target, only the mask remains visible, leading to impaired behavioral detection performance. These findings support the object-substitution hypothesis and provide new evidence that perception, attention, and awareness can be dissociated.

Adolescent↗
PubMed1998

The intubating laryngeal mask. Use in failed and difficult intubation.

The use of the intubating laryngeal mask in three patients is described. In two patients for whom tracheal intubation using traditional techniques had failed, the intubating laryngeal mask was used to achieve successful tracheal intubation. The trachea of one of these patients was subsequently re-intubated for a second procedure using the same technique. A third patient with a cervical spine fracture whose trachea was electively intubated using the intubating laryngeal mask is also presented.

Aged↗
PubMed1999

A comparison of two airway aids for emergency use by unskilled personnel. The Combitube and laryngeal mask.

Many non-anaesthetists find airway control and intubation difficult. The laryngeal mask has been advocated for use by non-anaesthetists at cardiorespiratory arrests, whilst the Combitube is said to provide protection from aspiration. We wished to determine which device was easiest for unskilled staff to use. Staff not previously trained in airway support were briefly taught insertion of each device. Twenty-six ASA 1 or 2 adults, requiring muscle relaxation and tracheal intubation for surgery, were recruited to this randomised crossover study. Both devices were inserted in random order and the time to successful ventilation of the lungs recorded. Both devices were successfully placed in 24/26 patients. The median times to insertion were 40 s and 45 s for the laryngeal mask and Combitube, respectively, with two failures, both with the Combitube (p > 0.05); these were due to faulty operator technique. The Combitube may be a suitable alternative to the laryngeal mask for use in resuscitation by unskilled staff.

Adult↗
PubMed1999

Conditions for laryngeal mask insertion. A comparison of propofol versus sevoflurane with or without alfentanil.

One hundred unpremedicated ASA 1 or 2 patients scheduled for elective surgery were divided equally into four groups and recruited into this prospective, randomised parallel groups study. Induction was with propofol 2.5 mg.kg-1 or vital-capacity breath induction with sevoflurane (> 7% in the inspiratory gas) in 65% nitrous oxide and oxygen, or gaseous induction with sevoflurane plus alfentanil 5 micrograms.kg-1 or propofol 2.5 mg.kg-1 and alfentanil 5 micrograms.kg-1. The conditions for laryngeal mask insertion were assessed and graded on a three-point scale using six variables. The overall condition for laryngeal mask insertion was assessed as excellent, satisfactory or poor on the basis of total score in each group. Excellent or satisfactory conditions were observed in 25 (100%) patients in the sevoflurane-alfentanil group, 22 (88%) in the propofol-alfentanil group and 16 (64%) patients each in the propofol and sevoflurane groups (p < 0.001). A sevoflurane-alfentanil combination provides better conditions for laryngeal mask insertion when compared with sevoflurane alone, or a propofol-alfentanil combination.

Adolescent↗
PubMed1999

Intubating laryngeal mask and rapid sequence induction in patients with cervical spine injury.

The Intubating Laryngeal Mask (FastrachTM), a modified conventional laryngeal mask airway, and its prototype cuffed silicone tube, continue to be an appropriate intubating tool in combination with fibreoptic bronchoscopy in the emergency situation. This is an account of two patients with suspected cervical spine fracture admitted to our emergency room in a haemodynamically unstable condition and requiring a rapid sequence induction of anaesthesia, in whom we successfully applied this newly developed intubating device for the first time. Provided that there are no intubation difficulties, direct laryngoscopy is still the fastest method of securing an airway; however, this procedure leads to an extension of the cervical spine, which may be hazardous in the case of a cervical spine injury. Intubation by means of the Intubating Laryngeal Mask avoids dangerous hyperextension of the occipito-atlanto-axial complex, a fact that we were able to verify by lateral cervical spine fluoroscopy during intubation.

Adult↗
PubMed1999

A comparison of two silicone-reinforced tracheal tubes with different bevels for use with the intubating laryngeal mask.

Seventy consecutive patients were randomly allocated for intubation through the intubating laryngeal mask airway using a straight reinforced silicone tracheal tube with either a conventional or a modified bevel. The conventional bevel was firm, wedge-shaped and with a leading edge at the side. The modified bevel was soft, hemispherical and with a leading edge in the midline. The intubating laryngeal mask position was adjusted until optimal ventilation was obtained and intubation was attempted using the randomised device. If tactile resistance was felt, a predetermined sequence of adjusting manoeuvres were utilised before a subsequent attempt. The first-attempt successful intubation rate with the conventional bevel was 23/37 (62%) and with the modified bevel was 28/33 (85%). The second-attempt successful intubation rate for the conventional bevel was 12/37 (32%) and for the modified bevel was 4/33 (12%). Intubation failed after three attempts for one patient in each group. Fewer overall intubation attempts were required with the modified bevel (p = 0.033). We conclude that intubation success rates through the intubating laryngeal mask with a straight silicone-reinforced tube are higher with a soft, hemispherical bevel with a leading edge in the midline compared with the firm, wedge-shaped bevel with a leading edge at the side.

Adult↗