Assessment of morbidity following insertion of fixed preoperative orthopedic appliance in infants with complete cleft lip and palate.

OBJECTIVE: To examine physiologic and behavioral indicators of pain within the first 24 hours following insertion of the fixed presurgical orthopedic appliance (FPOA) under general anesthesia in infants with unilateral and bilateral complete cleft lip and palate. METHODS: The study sample included 109 infants who had either a dentomaxillary appliance (DMA) or an elastomeric chain premaxillary retraction (ECPR) appliance. Vital signs and FLACC (Face, Legs, Activity, Cry, Consolability) scores were used to measure the outcomes. RESULTS: There was an initial postoperative increase in the median heart rate. Heart rate returned to the median baseline level by 8 hours. The median systolic blood pressure increased postoperatively and remained elevated throughout the time of evaluation. The median respiratory rate remained below that at baseline throughout the study period. The highest mean change in FLACC measurements was observed approximately 2 hours postoperatively. By 3 hours postoperatively, the scores decreased. CONCLUSIONS: Although there was a large individual variability, the FLACC scores became reduced after 3 hours following surgical insertion of the DMA and the ECPR appliance.

Multichannel speech intelligibility and talker recognition using monaural, binaural, and three-dimensional auditory presentation.

In a 3D auditory display, sounds are presented over headphones in a way that they seem to originate from virtual sources in a space around the listener. This paper describes a study on the possible merits of such a display for bandlimited speech with respect to intelligibility and talker recognition against a background of competing voices. Different conditions were investigated: speech material (words/sentences), presentation mode (monaural/binaural/3D), number of competing talkers (1-4), and virtual position of the talkers (in 45 degrees-steps around the front horizontal plane). Average results for 12 listeners show an increase of speech intelligibility for 3D presentation for two or more competing talkers compared to conventional binaural presentation. The ability to recognize a talker is slightly better and the time required for recognition is significantly shorter for 3D presentation in the presence of two or three competing talkers. Although absolute localization of a talker is rather poor, spatial separation appears to have a significant effect on communication. For either speech intelligibility, talker recognition, or localization, no difference is found between the use of an individualized 3D auditory display and a general display.

Fidelity of three-dimensional-sound reproduction using a virtual auditory display.

The fidelity of reproducing free-field sounds using a virtual auditory display was investigated in two experiments. In the first experiment, listeners directly compared stimuli from an actual loudspeaker in the free field with those from small headphones placed in front of the ears. Headphone stimuli were filtered using head-related transfer functions (HRTFs), recorded while listeners were wearing the headphones, in order to reproduce the pressure signatures of the free-field sounds at the eardrum. Discriminability was investigated for six sound-source positions using broadband noise as a stimulus. The results show that the acoustic percepts of real and virtual sounds were identical. In the second experiment, discrimination between virtual sounds generated with measured and interpolated HRTFs was investigated. Interpolation was performed using HRTFs measured for loudspeaker positions with different spatial resolutions. Broadband noise bursts with flat and scrambled spectra were used as stimuli. The results indicate that, for a spatial resolution of about 6 degrees, the interpolation does not introduce audible cues. For resolutions of 20 degrees or more, the interpolation introduces audible cues related to timbre and position. For intermediate resolutions (10 degrees - 15 degrees) the data suggest that only timbre cues were used.

Auditory distance perception in rooms.

The perceived distance of a sound source in a room has been shown to depend on the ratio of the energies of direct and reflected sound. Although this relationship was verified in later studies, the research has never led to a quantitative model. The advent of techniques for the generation of virtual sound sources has made it possible to study distance perception using controlled, deterministic stimuli. Here we present two experiments that make use of such stimuli and we show that a simple model, based on a modified direct-to-reverberant energy ratio, can accurately predict the results and also provide an explanation for the 'auditory horizon' in distance perception. The modification of the ratio consists of the use of an integration time of 6 milliseconds in the calculation of the energy of the direct sound. This time constant seems to be important in spatial hearing-the precedence effect is also based on a similar integration window.

Application of a three-dimensional auditory display in a flight task.

The effectiveness of a three-dimensional (3D) auditory display in conveying directional information was investigated in a flight simulation experiment. While flying a simulated fighter aircraft, participants followed a target aircraft that suddenly disappeared and reemerged at an unknown position. The task was to locate and trail the target as quickly as possible. In all conditions the participants viewed a computer-generated outside image, on which they could spot the target only when it was at short range, and a three-dimensional (3D) tactical display indicating the target position at all distances within a limited field of view. Additional displays were a bird's-eye-view radar display, which also indicated whether the target was above or below the own plane, and a 3D auditory display, which generated a warning sound from the relative direction of the target. The auditory display used individualized head-related transfer functions to create a virtual sound source and a head-tracking device to decouple the position of the source from head movements. Results show that the radar and auditory displays caused about the same significant reduction in search time in comparison with the tactical display only. A further reduction was found when the two additional displays were presented simultaneously.

A model for context effects in speech recognition.

A model is presented that quantifies the effect of context on speech recognition. In this model, a speech stimulus is considered as a concatenation of a number of equivalent elements (e.g., phonemes constituting a word). The model employs probabilities that individual elements are recognized and chances that missed elements are guessed using contextual information. Predictions are given of the probability that the entire stimulus, or part of it, is reproduced correctly. The model can be applied to both speech recognition and visual recognition of printed text. It has been verified with data obtained with syllables of the consonant-vowel-consonant (CVC) type presented near the reception threshold in quiet and in noise, with the results of an experiment using orthographic presentation of incomplete CVC syllables and with results of word counts in a CVC lexicon. A remarkable outcome of the analysis is that the cues which occur only in spoken language (e.g., coarticulatory cues) seem to have a much greater influence on recognition performance when the stimuli are presented near the threshold in noise than when they are presented near the absolute threshold. Demonstrations are given of further predictions provided by the model: word recognition as a function of signal-to-noise ratio, closed-set word recognition, recognition of interrupted speech, and sentence recognition.

Effect of multiple speechlike maskers on binaural speech recognition in normal and impaired hearing.

Speech-reception thresholds (SRT) were measured for 17 normal-hearing and 17 hearing-impaired listeners in conditions simulating free-field situations with between one and six interfering talkers. The stimuli, speech and noise with identical long-term average spectra, were recorded with a KEMAR manikin in an anechoic room and presented to the subjects through headphones. The noise was modulated using the envelope fluctuations of the speech. Several conditions were simulated with the speaker always in front of the listener and the maskers either also in front, or positioned in a symmetrical or asymmetrical configuration around the listener. Results show that the hearing impaired have significantly poorer performance than the normal hearing in all conditions. The mean SRT differences between the groups range from 4.2-10 dB. It appears that the modulations in the masker act as an important cue for the normal-hearing listeners, who experience up to 5-dB release from masking, while being hardly beneficial for the hearing impaired listeners. The gain occurring when maskers are moved from the frontal position to positions around the listener varies from 1.5 to 8 dB for the normal hearing, and from 1 to 6.5 dB for the hearing impaired. It depends strongly on the number of maskers and their positions, but less on hearing impairment. The difference between the SRTs for binaural and best-ear listening (the "cocktail party effect") is approximately 3 dB in all conditions for both the normal-hearing and the hearing-impaired listeners.

A clinical test for the assessment of binaural speech perception in noise.

The present paper describes a clinical test for the assessment of speech perception in noise. The test was designed to separate the effects of several relevant monaural and binaural cues. Results show that the performance of individual hearing-impaired listeners deviates significantly from normal for at least 2 of the following aspects: (1) perception of speech in steady-state noise; (2) relative binaural advantage due to directional cues; (3) relative advantage due to masker fluctuations. In contrast, both the hearing loss for reverberated speech and the relative binaural advantage due to interaural signal decorrelation, caused by reverberation, were essentially normal for almost all hearing impaired.

Binaural speech intelligibility in noise for hearing-impaired listeners.

The effect of head-induced interaural time delay (ITD) and interaural level differences (ILD) on binaural speech intelligibility in noise was studied for listeners with symmetrical and asymmetrical sensorineural hearing losses. The material, recorded with a KEMAR manikin in an anechoic room, consisted of speech, presented from the front (0 degree), and noise, presented at azimuths of 0 degree, 30 degrees, and 90 degrees. Derived noise signals, containing either only ITD or only ILD, were generated using a computer. For both groups of subjects, speech-reception thresholds (SRT) for sentences in noise were determined as a function of: (1) noise azimuth, (2) binaural cue, and (3) an interaural difference in overall presentation level, simulating the effect of a monaural hearing acid. Comparison of the mean results with corresponding data obtained previously from normal-hearing listeners shows that the hearing impaired have a 2.5 dB higher SRT in noise when both speech and noise are presented from the front, and 2.6-5.1 dB less binaural gain when the noise azimuth is changed from 0 degree to 90 degrees. The gain due to ILD varies among the hearing-impaired listeners between 0 dB and normal values of 7 dB or more. It depends on the high-frequency hearing loss at the side presented with the most favorable signal-to-noise (S/N) ratio. The gain due to ITD is nearly normal for the symmetrically impaired (4.2 dB, compared with 4.7 dB for the normal hearing), but only 2.5 dB in the case of asymmetrical impairment. When ITD is introduced in noise already containing ILD, the resulting gain is 2-2.5 dB for all groups. The only marked effect of the interaural difference in overall presentation level is a reduction of the gain due to ILD when the level at the ear with the better S/N ratio is decreased. This implies that an optimal monaural hearing aid (with a moderate gain) will hardly interfere with unmasking through ITD, while it may increase the gain due to ILD by preventing or diminishing threshold effects.

[Causes and results of reoperations following stapedectomy]. / Oorzaken en resultaten van heroperaties na stapedectomie.

The records of 145 patients who underwent revision stapedectomy were analysed to determine the causes of failure of the previous operation, the hearing results and the postoperative complaints. Displacement of the prosthesis was the most common cause of failure (49%). Other surgical findings, sometimes in combination, were a short prosthesis (35%), middle ear adhesions (23%), otosclerotic regrowth (14%) and eroded incus (10%). No specific cause of failure was identified in 6% of the revisions. Thirty-eight per cent of revision operations resulted in a hearing gain to a level less than 10 dB conduction loss and 61% to less than 20 dB. Slight sensorineural hearing loss after revision surgery occurred in 5%. 'Dead ears' were encountered in 2% as against 0.6% in the primary cases. Tinnitus was the most common complaint (21%) at the 3 week postoperative follow-up, declining to 7% four months postoperatively.

The effect of head-induced interaural time and level differences on speech intelligibility in noise.

A study was made of the effect of interaural time delay (ITD) and acoustic headshadow on binaural speech intelligibility in noise. A free-field condition was simulated by presenting recordings, made with a KEMAR manikin in an anechoic room, through earphones. Recordings were made of speech, reproduced in front of the manikin, and of noise, emanating from seven angles in the azimuthal plane, ranging from 0 degree (frontal) to 180 degrees in steps of 30 degrees. From this noise, two signals were derived, one containing only ITD, the other containing only interaural level differences (ILD) due to headshadow. Using this material, speech reception thresholds (SRT) for sentences in noise were determined for a group of normal-hearing subjects. Results show that (1) for noise azimuths between 30 degrees and 150 degrees, the gain due to ITD lies between 3.9 and 5.1 dB, while the gain due to ILD ranges from 3.5 to 7.8 dB, and (2) ILD decreases the effectiveness of binaural unmasking due to ITD (on the average, the threshold shift drops from 4.6 to 2.6 dB). In a second experiment, also conducted with normal-hearing subjects, similar stimuli were used, but now presented monaurally or with an overall 20-dB attenuation in one channel, in order to simulate hearing loss. In addition, SRTs were determined for noise with fixed ITDs, for comparison with the results obtained with head-induced (frequency dependent) ITDs.(ABSTRACT TRUNCATED AT 250 WORDS)

Cooperation between cytotoxic and helper T lymphocytes in protection against lethal Sendai virus infection. Protection by T cells is MHC-restricted and MHC-regulated; a model for MHC-disease associations.

The in vivo importance of class I MHC regulation of the Tc response to a natural pathogenic agent of high virulence was studied on the basis of our previous demonstration of a major difference in the capacity to generate a Sendai virus-specific Tc response between C57BL/6 (B6, H-2b) mice and H-2Kb mutant B6.C-H-2bm1 (bm 1) mice. These two mouse strains differ from each other only in three amino acids in the crucial H-2Kb restriction element for this response. bm 1 mice, in contrast to B6 mice, are Tc nonresponders against this virus, but show Sendai-specific T cell proliferation, antibody production, and DTH reactions, as well as NK cell activity, equal to those of B6 mice. B6, Sendai Tc-deficient bm 1 and T cell-deficient B6 nu/nu mice differ from each other in susceptibility to lethal pneumonia induced by i.n. inoculation of virulent Sendai virus. The lethal dose (LD50) in B6 mice averaged 152 TCID50, in bm 1 mice, 14 TCID50 and in B6 nu/nu mice 0.5 TCID50. The importance of Tc was also shown by the complete protection of B6 nu/nu mice against infection with a lethal virus dose by i.v. injection of a Sendai virus-specific, IL-2-dependent and H-2Kb-restricted B6 Tc clone. In vivo protection by this Tc clone was H-2Kb-restricted. Apart from Tc, an important role for virus-specific Th cells is evident from the difference in susceptibility between bm 1 and B6 nu/nu mice. This conclusion was supported by the demonstration that the mean survival time of B6 nu/nu and bm 1 nu/nu mice could be significantly prolonged, in an I-Ab-restricted manner, by the injection of in vitro-propagated, Sendai-specific B6 or bm 1 Th clones after a lethal dose of Sendai virus, and by the demonstration that inoculation of these Th clones provided help to virus-specific Tc by means of IL-2 production. Strikingly, Th and Tc cooperate in anti-Sendai virus immunity, since permanent survival of lethally infected nu/nu mice was only achieved by inoculation of a mixture of Tc and Th clones or a mixture of a Tc clone and rIL-2. This study provides a unique model for the study of MHC-disease associations.

Covalent binding of BP-metabolites to DNA of cultured human hair follicle keratinocytes.

Primary cultures of human hair follicle keratinocytes were established by using a basement membrane-like growth substrate, the bovine eye lens capsule. A method was adapted for the isolation of 3H-benzo(a)pyrene (BP)-modified DNA from the cellular outgrowth of only one hair follicle (approximately 2 X 10(5) cells). In a routine procedure hair follicle keratinocytes were incubated with 0.5 microM 3H-BP for 24 h. The purified DNA was subjected to enzymic hydrolysis and the adducts were analyzed by Sephadex LH-20 column chromatography followed by HPLC. Only one major adduct, which represented 60-80% of the total radioactivity which can be confined to modified nucleosides in the LH-20 chromatograph, could be identified. This adduct co-chromatographed with the marker adducts resulting from the trans-addition of the N-2-amino group of guanine to the 10-position of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene. Co-incubation with 7,8-benzoflavone (0.3 microM), an inhibitor of cytochrome P-448, and with 1,1,1-trichloropropene-2,3-oxide (0.2 microM), an inhibitor of epoxide hydrolase, resulted in a marked inhibitory effect (15% of the control binding) and a large increase (300% of the control value) in BP-DNA binding respectively. Induction of aryl hydrocarbon hydroxylase activity in the cultures with 5,6-benzoflavone (10 microM) or benz(a)anthracene (10 microM) caused a decrease (75 and 46% of the control value respectively) in BP-DNA binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Phase relationship between bone and air conducted impulse signals in the human head.

Using the cancellation method we investigated the phase relationship as well as the amplitude ratio between impulse signals transmitted simultaneously via both bone and air conduction channels. The psychophysical findings indicated a phase difference corresponding to a time delay of about 0.9 ms by which the air input led the bone input in the case of frontal bone stimulation. Changing the polarity of the bone conduction signal a maximum in the loudness sensation was found just in the same phase difference. The psychophysical findings, predicted mathematically, were verified with brainstem evoked potentials elicited to similar signals. Preliminary results showed that the time lag observed relied on the location of the bone vibrator on the head and furthermore on the frequency used. This suggests different transmissions of vibratory energy reaching the inner ear along the skull.