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Biomedical subjects

E S Luschei

Publications and source records attributed to E S Luschei.

At least 19 recordsLinked to original sources
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↗
PubMed1982

Morphologic alterations in Macaca mulatta following destruction of the motor nucleus of the trigeminal nerve.

In two adolescent male Macaca mulatta monkeys, small unilateral electrolytic lesions were produced in the motor nucleus of the trigeminal nerve. The side contralateral to the muscle paralysis served as the control side. The animals were killed 130 and 300 days postoperatively. One animal (animal A) was prepared as a dry skull preparation. Alterations in craniofacial form were noted clinically in both animals and included paralysis and atrophy of the muscles of mastication on the lesion side and mandibular asymmetry. In animal A (300 days postoperative survival), alterations in form included dental and mandibular asymmetry, the appearance of an anterior open-bite on the affected side, and a decrease in the size of the intratemporal fossa on the affected side. Remodeling changes were evident in the condylar process, the zygomatic arch, the orbit, and the zygomaticotemporal and zygomaticofrontal sutures on the lesion side but were not apparent on the contralateral side.

Animals↗
PubMed1980

Alterations in the facial skeleton of the guinea pig following a lesion of the trigeminal motor nucleus.

In thirty-three of sixty-six guinea pigs of the Topeka strain small, unilateral, electrolytic lesions were produced in the motor nucleus of the trigeminal nerve. Unoperated animals and the side contralateral to the muscle paralysis served as controls. Lesions were created when animals were 15 days or 75 days of age, and the animals were killed 15, 30, 45, or 60 days postoperatively. Each animal was subjected to dry skull preparations or radiographic and histologic techniques. Alterations in craniofacial form were noted in both the growing animals and the animals with little growth remaining. Alterations in form and function included paralysis and atrophy of the muscles of mastication on the lesion side, hypereruption of teeth, and reduction in growth of facial bones on the lesion side. Remodeling changes were evident in the glenoid fossa, the condylar process, and the coronoid process on the operated side but were not apparent in the contralateral control or the unoperated control animal.

Animals↗
PubMed1980

Evidence that the human jaw stretch reflex increases the resistance of the mandible to small displacements.

1. Small 'step' or sinusoidal displacements were imposed on the mandible while human subjects maintained an average biting force of 10 N. Phase-related changes in the force resisting sinusoidal displacement were used to determine the mechanical stiffness of the human mandibular system as a function of the frequency of stretching. 2. Jaw-muscle electromyographic (e.m.g.) responses to 'step' stretches were of 8 msec latency and generated a very substantial force response. Jaw-muscle e.m.g. responses having longer latency were not observed. 3. The mechanical stiffness of the human mandible was relatively constant as a function of the frequency of stretching, having a typical magnitude of about 15 N/mm (+/- 200 micrometers stretch) or 10 N/mm (+/- 1500 micrometers stretch) at mean biting forces of 10 N. The force resisting displacement was phase-advanced at all frequencies. 4. Modulation of jaw muscle electrical activity evoked by sinusoidal stretches increased in amplitude as a function of increasing stretch frequency. E.m.g. modulation was 60--100 degrees advanced at frequencies of 1--10 Hz, but the phase decreased at higher frequencies, becoming negative (lagging stretch) at frequencies of 30 Hz and above. These characteristics are consistent with the idea that the jaw stretch reflex is dependent on jaw muscle spindle afferent fibres exciting jaw-closing motoneurones by relatively direct (but not necessarily monosynaptic) connexions. 5. The relationship between jaw-muscle activity and voluntary fluctuations of isometric biting force suggests that human jaw muscles can be modelled as a second-order linear 'filter'. The corner frequency for human jaw muscle is about 3 Hz; thus it would appear to be considerably slower than jaw muscle of monkeys. 6. The reflex stiffness of the human mandible, estimated quantitatively on the assumption that human jaw muscle stiffness is similar to the intrinsic stiffness of the gastrocnemius of the cat, ranges between 5 and 9 N/mm at frequencies between 1 and 8 Hz. Since this reflex stiffness is about the same as muscle stiffness in this frequency range, we conclude that the stretch reflex of the human mandible contributes functionally to its postural stability. 7. Reflex stiffness appears to be greater in the monkey mandible relative to muscle stiffness than in the human mandible. The difference is argued to be a manifestation of the difference in jaw muscle contraction speed between the two species. 8. The fact that the mandibular stretch reflex appears to be stronger than the stretch reflex of the limbs of intact animals and humans is discussed in terms of the special anatomical and functional features of the mandible.

Adult↗
PubMed1979

Temporomandibular joint meniscectomy--effects on joint structure and masticatory function in macaca fascicularis.

The postoperative effects of unilateral temporomandibular joint meniscectomy on joint structure and masticatory function were evaluated in four mature Macaca fascicularis and compared with one control. Mandibular movement during mastication was monitored objectively with an optoelectronic tracking system within four months and again within twelve months postmeniscectomy in each animal. Temporomandibular joint structure was documented radiographically and histologically. Results showed that degenerative joint disease was produced in the postsurgical joint, and that the morphological changes were location-dependent. Fibrous ankylosis was observed histologically in three animals. The contralateral joints were not affected morphologically, except for bony resorption of the articular eminence noted microscopically in one animal. Radiographically, however, the joint appeared normal. Variable alterations in masticatory patterns were observed following unilateral meniscectomy. While there appeared to be an association between temporomandibular joint structure and masticatory function, radiographic and microscopic observation of morphological alterations in the joint did not result in predictable functional limitations in chewing pattern.

Animals↗
PubMed1978

The strength of the reflex response to sinusoidal stretch of monkey jaw closing muscles during voluntary contraction.

1. Rhesus monkeys were trained to exert steady biting forces of 3--60 N for 1--2 sec. This behaviour was well maintained while sinusoidal or step opening and closing movements were imposed on the jaw. 2. The amplitude of the force modulation during sinusoidal stretching was divided by the amplitude of movement to obtain the magnitude of stiffness. This estimate was made at frequencies from 2 to 50 Hz at amplitudes of 100 and 500 micrometer (half the peak-to-peak movement at the incisors). 3. Peak magnitudes of stiffness were seen with frequencies of 8--15 Hz when the amplitude of movement was small; there was a great deal of variation between individual animals. This variation was most striking with mean forces of 25--35 N. The stiffness was greatest in animals that showed considerable spontaneous tremor, and the highest levels of stiffness were often recorded with frequencies near which tremor amplitude was large. A marked phase lag in the force response was often seen during small amplitude stretching at 8--30 Hz. 4. Estimates of stiffness for larger amplitude (500 micrometer) stretching showed less variation; the magnitude of stiffness showed maximum values below 10 Hz and a minimum at 15--30 Hz. Force always showed a phase lead on position although this lead became small in the frequency range where with smaller movement there had been phase lags. The magnitude of stiffness increased with increasing mean force. 5. Bilateral electrolytic lesions were made in the brain stems of three animals; they reduced by over 95% the expected number of cells in the mesencephalic nucleus of the fifth cranial nerve on either side. These lesions interrupted the afferent pathway for the stretch reflex and so abolished excitatory electromyogram (e.m.g.) responses to step stretches of the jaw closing muscles. 6. Such reflex responses as persisted after the lesions were small and inhibitory. E.m.g. silences followed both step stretch and release; the response to release was a 'load compensation' that could not be attributed to spindle afferents. 7. After the lesions the responses to movements of 100 micrometer showed neither negative values for the phase nor marked peaks in the stiffness magnitude at low frequencies; these features therefore take origin in the action of the stretch reflex. The stiffness that was measured after the lesions may be attributed to the non-reflex components resisting stretch, particularly to the properties of the contracting muscles. Thus, the phase of the force response was markedly advanced at all frequencies and the stiffness seen for 100 micrometer was similar to that for 500 micrometer. Stiffness increased with increasing mean force, as before surgery. 8. Vector subtraction of the stiffness seen at each frequency after interrupting the stretch reflex from that seen before doing so gave a quantitative estimate of the strength of the stretch reflex. The reflex activity calculated in this way showed attenuation and progressive phase lag as the frequency increased above 10 Hz...

Afferent Pathways↗
PubMed1975

Role of monkey precentral cortex in control of voluntary jaw movements.

Monkeys were trained to produce a low, steady biting force for 0.5-2.5 s, and then a rapid forceful bite in response to a visual stimulus. After large bilateral lesions of the precentral face area, monkeys emitted repetitive forceful bites on the apparatus, but could not perform the force-holding task. They eventually relearned the task, but the force exerted was never as steady as it was prelesion, and often oscillated at about 2 and/or 5-6 Hz. After retraining, two animals with large bilateral lesions of the face area produced median RT responses equal to or only slightly longer than their prelesion performance, indicating that neural pathways not involving the precentral cortex can mediate quick visual RT responses. The variability of RTs was permanently increased, probably as a result of the persistent unsteadiness of the force-holding response. Incomplete bilateral lesions of the precentral face area, a complete unilateral lesion of that area, and bilateral lesions adjacent regions of cortex produced either mild, transient difficulties with the biting taks, or no problems at all. The results indicate that the precentral cortex has a role in the control of voluntary jaw movements. Lesions caused difficulty in controlling, but not producing, closing jaw movements, thereby suggesting that this role is predominantly to inhibit jaw-closing motoneurons or the systems that excite them. Electrical stimulation studies of the face area of the precentral cortex of the unanesthetized monkey point to the same conclusion.

Animals↗