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Biomedical subjects

E S Luschei

Publications and source records attributed to E S Luschei.

At least 37 records · Page 2Linked to original sources
PubMed1995

Fundamental frequency and tracheal pressure during three types of vocalizations elicited from anesthetized dogs.

Electrical stimulation of the midbrain was used to elicit a variety of vocalizations from six anesthetized dogs. This study was conducted to investigate the ranges of and relationships between fundamental frequency of the vocalizations (F0) and tracheal pressure (Pt) produced during the vocalizations. The vocalizations were described according to type (growl, howl, and whine); F0 and Pt, as well as patterns of laryngeal muscle activity, were examined for each vocalization type. Natural-sounding growl and howl vocalizations were elicited from five dogs; three dogs also produced whines. With few exceptions, F0 was categorically different for the three vocalization types (low for growls, average for howls, very high for whines). Pt values overlapped for the three vocalization types, although, on average, howls were produced with greater Pt than growls. Patterns and degrees of laryngeal muscle activity varied across and within vocalization types, but general findings were consistent with the presumed function of most of the muscles. Laryngeal muscle activity may help explain some of the variability in the acoustic and aerodynamic data.

Anesthesia↗
PubMed1994

Interference between normal vibrato and artificial stimulation of laryngeal muscles at near-vibrato rates.

A stabilized tremor hypothesis for vocal vibrato is investigated. The stabilizer is assumed to be a mechanical oscillator that may contain reflex loops. Artificial stimulation of the cricothyroid muscle in one subject showed a well-defined resonance curve of this peripheral oscillator at approximately 5.0 Hz. Combined artificial stimulation with natural vibrato showed that the vibrato could be entrained by a peripheral stimulus, provided the two frequencies are separated by no more than approximately +/- 0.5 Hz. This suggests that vibrato frequencies are not "hard-wired" centrally, even though a collection of centrally generated tremors may serve as excitation to the peripheral oscillator.

Electric Stimulation↗
PubMed1994

Modulation of fundamental frequency by laryngeal muscles during vibrato.

The variations in voice fundamental frequency (F0) that occur during vibrato production may be produced, at least in part, by modulation of laryngeal muscle activity. We have quantified this relation by using a cross-correlation analysis of the changes in F0 during vibrato and the changes either in motor unit firing rate or in gross electromyographic activity from the cricothyroid (CT) and the thyroarytenoid (TA) muscles. Two trained amateur tenors provided the data. Correlations were generally quite strong (mean r for the CT was 0.72 for singer 1 and 0.50 for singer 2; mean r for the TA was 0.31 for singer 2), thus providing support for previous evidence that fundamental frequency modulation in vibrato involves active modulation of the laryngeal motoneuron pool, especially by the CT muscle. In addition, phase delays between muscle modulation and changes in fundamental frequency were substantial (averaging approximately 130 degrees for the CT and 140 degrees for the TA). This finding may help provide insight regarding the mechanisms responsible for the production of vibrato.

Electromyography↗
PubMed1994

Effect of subglottic pressure on fundamental frequency of the canine larynx with active muscle tensions.

The relation between subglottic pressure and the fundamental frequency of vocal fold vibration was studied by means of evoked phonation in an in vivo canine model. The evoked-phonation model involved electrical stimulation of the midbrain that resulted in consistent responses by respiratory and laryngeal musculature, accompanied by phonation. The dynamic stiffness properties of the vocal folds, especially the "cover," were investigated by delivering various amounts of air pressure to the larynx from an opening in the trachea. The fundamental frequency of vocal fold vibration increased linearly with subglottic pressure. The slopes ranged from 22.4 to 118.7 Hz per kilopascal in 7 animals. The results indicated that the dependence of fundamental frequency on subglottic pressure is a passive mechanical phenomenon.

Animals↗
PubMed1994

A preliminary study of the prognostic role of electromyography in laryngeal paralysis.

Confidence in the reliability of laryngeal electromyography to predict recovery is critical if this tool is to be used to select the type and timing of surgical intervention. The characteristics of electromyography of 14 patients with unilateral vocal fold paralysis were assessed to determine which factor or combination of factors would be most useful in determining prognosis. We examined the duration, amplitude, waveform morphology, root-mean-square, and time interval from onset to electromyography recording. The results supported the concept that electromyography recordings are valuable in determining prognosis if performed before 6 months and preferably within 6 weeks of onset of laryngeal paralysis. A positive prognosis for laryngeal recovery was indicated when the following electromyography features were present in the immobile vocal fold: (1) normal motor unit waveform morphology, (2) overall electromyography activity characterized by a root-mean-square value greater than 40 microV in any one task, and (3) no electrical silence during voluntary tasks. On the basis of this criteria our overall correct prognostic rate was 89%.

Electromyography↗
PubMed1993

Air pressure regulation during speech production.

Vocal tract pressures during speech tend to be maintained in the face of airway leaks that might be encountered by individuals with repaired palatal clefts. This study tested the hypothesis that such constant pressures can be explained as a consequence of constant pressure source characteristics of the respiratory system during speech production. This conceptualization differs from pressure regulation theories [e.g., D. Warren, Cleft Palate J. 23, 251-260 (1986)] which posit that active reflexive compensatory responses occur to regulate air pressure during speech. Four experiments were conducted to (a) confirm the distinction between constant flow versus constant pressure sources using a plastic vocal tract model, (b) compare air pressure and flow patterns associated with airway leaks in normal speakers to model data, (c) study the effects of gas density in the vocal tract model on air pressure and air flow patterns predicted by a nonreflexive constant pressure source hypothesis, and (d) compare air pressure and air flow patterns associated with airway leaks obtained from normal speakers using different gas densities to model data. Overall, observed flow and pressure patterns suggest the possible influence of constant pressure source characteristics of the respiratory system during speech on maintenance of intraoral air pressure.

Adult↗
PubMed1993

Bipolar hooked-wire electromyographic technique in the evaluation of pediatric vocal cord paralysis.

Laryngeal electromyography is a valuable test to assess vocal cord paralysis in adults. This technique can be applied and adapted to the pediatric patient. In the operating room under general anesthesia and endoscopic guidance, bipolar hooked-wire electrodes are passed percutaneously through the anterior neck skin into both thyroarytenoid muscles. Electromyographic signals are evaluated during light anesthesia and on awakening. A critical appraisal of this technique is presented, including an analysis of sources of electrical interference in the operating room.

Adolescent↗
PubMed1992

Validation of a modern miniature transducer for measurement of interlabial contact pressure during speech.

The response characteristics of the Entran Flatline pressure transducer (EPL-2001-10) and its potential for use in studies of speech production were investigated. Data from a model simulating bilabial closure and from 2 human subjects indicate that this transducer is an appropriate tool for measurement of interlabial pressure during production of bilabial consonants. That is, the onset of the pressure pulse corresponds to the initiation of lip contact between the upper and lower lips, and the return to baseline represents complete lip separation, thus eliminating the need to infer lip contact from records of lip movement. Transducer output is not influenced significantly by temperature fluctuations or changes in the configuration and stiffness of the lips. The frequency response and level of sensitivity are linear over the range of pressures produced during speech. The subjects in this study typically generated interlabial pressures of 1.0-3.0 kPa during production of [p] in a carrier phrase.

Body Temperature↗
PubMed1992

Tongue strength and endurance: relation to highly skilled movements.

Tongue strength and endurance (fatigue) were examined in subjects who have acquired high skill levels with their tongues (supranormal) and in subjects who use the tongue normally. The supranormal groups were trumpet players and high school debaters who were able to speak intelligibly at rates much faster than normal. Hand strength and fatigue were also assessed. Maximal strength was measured by recording how much pressure an individual could exert on an air-filled bulb. Endurance was measured by determining how long subjects could sustain 50% of their maximal pressure. Results showed that maximal strength of the tongue and hand did not differentiate the supranormal subjects from the normal subjects. Hand endurance did not differentiate the subjects either. However, the supranormal groups had significantly longer tongue endurance times than did the normal subjects.

Adult↗
PubMed1989

Electrical activity from the superior pharyngeal constrictor during reflexive and nonreflexive tasks.

The purpose of this investigation was to determine, in a quantitative manner, which, if any, nonswallowing tasks produce significant levels of activation in the superior pharyngeal constrictor muscle of normal human subjects. Bipolar hooked wire electrodes were inserted in the superior pharyngeal constrictor muscle of 15 healthy subjects. Electrode placement was controlled. Each subject performed two reflexive tasks, six voluntary tasks requiring phonation, and four nonspeech voluntary tasks. The electromyogram (EMG) was rectified and integrated. The resulting number was then transformed by taking its natural logarithm. An ANOVA was performed and a linear model was estimated. The magnitude of the EMG activity was related to the location of the electrodes. The largest values were recorded in the lateral-superior placement, followed by the lateral-inferior, medial-inferior and medial-superior. The superior pharyngeal contrictor was found to be a muscle activated primarily during reflexive activity. There was a general trend in the amplitude of EMG activity in relationship to task. Swallowing produced the greatest amount of activity and a gag produced about 60% of the activity produced by the swallow. Two tasks, production of the work /hok/ in which the phoneme /k/ was stressed, and a "modified Valsalva," which was actually a hard /k/ held for several seconds, produced the next greatest level of EMG.

Adult↗
PubMed1987

Central projections of the mesencephalic nucleus of the fifth nerve: an autoradiographic study.

Projections of cells of the mesencephalic nucleus of the fifth nerve (Mes V) to brainstem structures in the cat were studied by labelling Mes V cells with tritiated leucine. Before the leucine injections were made, however, large kainic acid lesions were produced in the vicinity of Mes V cells because these neurons are resistant to being killed or injured by this neurotoxin. Thus Mes V cells were selectively labelled by the leucine even though they are scattered among many other neurons. Leucine injections near Mes V cells located in the mesencephalon, which are primarily the somata of jaw muscle spindle afferent fibers, produced essentially the same pattern of terminal labelling as injections near a caudally located group of Mes V cells that includes the somata of many tooth mechanoreceptive afferents. Labelling was dense above the trigeminal motor nucleus in the nucleus supratrigeminalis and in the most medial portion of the principal trigeminal sensory nucleus. A scattering of labelled axons and diffuse label was seen along the length of the tract of Probst, which follows the medial border of the descending trigeminal sensory nucleus as far caudally as the dorsal motor nucleus of the vagus. Labelling within most of the trigeminal motor nucleus, which is known to receive direct synaptic input from Mes V cells, was very light. The only reasonably dense region of label was confined to a small dorsolateral portion of the motor nucleus. Although Mes V has generally been supposed to be involved with jaw control in a direct, reflexive manner, the extensive projections to nucleus supratrigeminalis and parts of the trigeminal sensory system draw attention to the potential proprioceptive sensory contribution of Mes V.

Animals↗
PubMed1987

Responses of neurons in nucleus supratrigeminalis to sinusoidal jaw movements in the cat.

Single neurons in the mesencephalic nucleus of the fifth nerve and in the rostral brain stem of barbiturate-anesthetized cats were studied in terms of their response to sinusoidal jaw movements at different frequencies and amplitudes. Units were quantitatively characterized by magnitude and phase of their firing rate modulation as a function of frequency, the linearity of their response at 5 Hz, and the variability of the interpsike intervals. Units were qualitatively characterized in terms of their response to gentle palpation of jaw muscles. Neurons were found in the nucleus supratrigeminalis that were selectively driven by jaw movement and that responded to gentle palpation to one or more ipsilateral jaw muscles. The magnitude of the sensitivity of these neurons as a function of frequency was not significantly different from cells of the mesencephalic nucleus of the fifth nerve. The phase of the sensitivity was, however, significantly more advanced than were those cells at all but the highest frequencies. The typical interspike interval variability of cells in nucleus supratrigeminalis was about 40% of the mean interval, whereas that variability of neurons of the mesencephalic nucleus of the fifth nerve was only about 10% of the mean interval. Supratrigeminal cells could relay jaw proprioceptive information to the cerebellum or thalamus.

Action Potentials↗
PubMed1983

Assessment of oral-motor reflexes in stutterers and normal speakers: preliminary observations.

Reflex responses of nine stutterers and nine normal speakers to low-level tactile and auditory stimuli were measured as changes in isometric molar biting force and masseter muscle activity. Tactile stimuli (mechanical displacement of the tissue) were applied to five intraoral and perioral sites. The acoustic stimulus was noise gated on for 12 msec. These low-level stimuli significantly modulated jaw-closing force and muscle activity in most of the subjects tested. In general, the initial effect of both auditory and tactile stimuli was suppression, although the initial response was excitation in some subjects with some forms of tactile stimulation. Within both groups of subjects, the amplitude and direction of reflex responses, particularly to mechanical stimuli, were highly variable between subjects, but these measures were stable within an individual over repeated tests.

Adult↗
PubMed1983

Effects of frequency-modulated auditory tones on the voice fundamental frequency in humans.

The sensitivity of audio-laryngeal reflex pathways to sinusoidal changes in the fundamental frequency of complex auditory tones (AF0) was assessed indirectly in three young adult human subjects. The subjects sustained phonation at constant voice fundamental frequency (VF0) and voice intensity while listening to a sawtooth tone whose AF0 varied over time in a sinusoidal fashion (rates = 5-13 Hz). The subjects phonated at a low voice intensity so that the intensity of the auditory tone (80-85 dB SL) completely masked their voice. Using computer signal averaging and Fourier analysis techniques it was found that the sinusoidally modulated AF0 induced similar modulations in the VF0 signal. The VF0 modulations were extremely small in amplitude and showed large phase shifts relative to the auditory input. These findings are discussed in relation to the role of auditory feedback in phonatory control.

Adult↗
PubMed1983

Jaw muscle afferent firing during an isotonic jaw-positioning task in the monkey.

The activity of jaw muscle receptors was studied by recording neurons in the mesencephalic nucleus of the trigeminal nerve in monkeys trained to control the position and movement of their mandible. Jaw position was measured by a weighted lever resting on the mandibular incisors. The force required to maintain the position of the lever was varied; in most cases it was either 25 or 360 g. Firing rates of neurons were related to stationary mandibular positions and to the velocity of movements during intervals when the movement velocity was constant. Of 49 neurons studied in detail, 21 fired at rates that were consistently and linearly related to static incisal openings. This static position sensitivity was typically about 5 spikes/mm of incisal opening. Most position-sensitive neurons fired at higher rates during opening movements and at lower rates during closing movements than would be accounted for by their position sensitivity. This sensitivity to the velocity of movement was not linear, however; slow closing movements sometimes did not produce a decrease in firing rate, and an actual increase during muscle shortening was seen in a few instances. The position sensitivity of eight neurons was evaluated during different loading conditions; in no case did it change substantially. Of the remaining 28 neurons, 26 fired at high rates during all opening movements and either stopped firing or fired at low, sporadic rates during closing movements. The static position sensitivity of these neurons was weak and variable both within and between neurons. The velocity sensitivity of these stretch-sensitive neurons was very nonlinear. Except for a range of slow movements (+/- 5 mm/s), the firing rate was maximal (200 spikes/s or higher) for most opening movements and zero for most closing movements. Maximal firing rates were higher when the loads being moved were increased from 25 to 360 g. The majority of position-sensitive neurons exhibited a large interspike-interval variability at wide incisal opening. In most of these neurons, this interspike-interval variability was periodic, usually at a rate of about 10 periods/s, and took the form of "saw-tooth" modulation on a record of instantaneous firing rate. Neurons that exhibited this modulation in a very prominent form also exhibited, in many instances, a substantial increase in firing rate during closing jaw movements.

Afferent Pathways↗