- Professor, Physiology
- Professor, Evelyn F Mcknight Brain Institute
- Professor, BIO5 Institute
- Professor, Speech/Language and Hearing
- Excellence in Mentoring
- The University of Arizona Honors College, Spring 2017
No activities entered.
DissertationPS 920 (Fall 2020)
Human Anat+Physiology IIPSIO 202 (Fall 2020)
DissertationPS 920 (Spring 2020)
Honors ThesisECOL 498H (Spring 2020)
ResearchPS 900 (Spring 2020)
Respiratory PhysiologyPSIO 450 (Spring 2020)
DissertationPS 920 (Fall 2019)
Honors ThesisECOL 498H (Fall 2019)
Human Anat+Physiology IIPSIO 202 (Fall 2019)
DissertationPS 920 (Spring 2019)
Honors ThesisPSIO 498H (Spring 2019)
Independent StudyECOL 399 (Spring 2019)
Respiratory PhysiologyPSIO 450 (Spring 2019)
DissertationPS 920 (Fall 2018)
Honors ThesisPSIO 498H (Fall 2018)
Human Anat+Physiology IIPSIO 202 (Fall 2018)
ResearchPS 900 (Summer I 2018)
DissertationPSIO 920 (Spring 2018)
ResearchPSIO 900 (Spring 2018)
Respiratory PhysiologyPSIO 450 (Spring 2018)
Human Anat+Physiology IIPSIO 202 (Fall 2017)
ResearchPSIO 900 (Fall 2017)
Honors ThesisPSIO 498H (Spring 2017)
Independent StudyPSIO 399 (Spring 2017)
Independent StudyPSIO 599 (Spring 2017)
Methods In NeuroscienceNRSC 700 (Spring 2017)
ResearchPSIO 900 (Spring 2017)
Respiratory PhysiologyPSIO 450 (Spring 2017)
Honors ThesisPSIO 498H (Fall 2016)
Human Anat+Physiology IIPSIO 202 (Fall 2016)
Research Methods In PsioPSIO 610 (Fall 2016)
ResearchPSIO 900 (Summer I 2016)
Independent StudyPSIO 699 (Spring 2016)
ResearchPSIO 900 (Spring 2016)
Respiratory PhysiologyPSIO 450 (Spring 2016)
Rsrch Meth Psio SciPS 700 (Spring 2016)
- Craighead, D. H., Heinbockel, T. C., Hamilton, M. N., Bailey, E. F., MacDonald, M. J., Gibala, M. J., & Seals, D. R. (2019). Time-efficient physical training for enhancing cardiovascular function in midlife and older adults: promise and current research gaps. Journal of applied physiology (Bethesda, Md. : 1985), 127(5), 1427-1440.More infoCardiovascular diseases (CVD) remain the leading cause of death in developed societies, and "midlife" (50-64 yr) and older (65+) men and women bear the great majority of the burden of CVD. Much of the increased risk of CVD in this population is attributable to CV dysfunction, including adverse changes in the structure and function of the heart, increased systolic blood pressure, and arterial dysfunction. The latter is characterized by increased arterial stiffness and vascular endothelial dysfunction. Conventional aerobic exercise training, as generally recommended in public health guidelines, is an effective strategy to preserve or improve CV function with aging. However,
- Sheel, A. W., & Bailey, E. F. (2020). Mechanisms of respiratory modulation of cardiovascular control. Journal of applied physiology (Bethesda, Md. : 1985), 128(1), 212-213.
- Bailey, E. F. (2018). Daily inspiratory muscle training lowers blood pressure and vascular resistance in healthy men and women. Experimental Physiology.
- Bailey, E. F. (2017). Association between Laryngeal Airway Aperture and the Discharge Rates of Genioglossus Motor Units. Frontiers in Physiology.
- Bailey, E. F. (2017). Association between laryngeal airway aperture and the discharge of genioglossus motor units. Frontiers in Respiratory Physiology.
- Bailey, E. F. (2017). Vocal tract configuration for breathing and speech sound production. Global Imaging Insights.
- DeLucia, C. M., De Asis, R. M., & Bailey, E. F. (2018). Daily inspiratory muscle training lowers blood pressure and vascular resistance in healthy men and women. Experimental physiology.More infoWhat is the central question of this study? What impact does inspiratory muscle training have on systemic vascular resistance, cardiac output and baroreflex sensitivity in adult men and women? What is the main finding and its importance? Inspiratory muscle training exerts favorable effects on blood pressure, vascular resistance and perception of stress. This exercise format is well-tolerated and equally effective whether implemented in men or women.
- LaCross, A., Watson, P. J., & Bailey, E. F. (2017). Association between Laryngeal Airway Aperture and the Discharge Rates of Genioglossus Motor Units. Frontiers in physiology, 8, 27.More infoWe know very little about how muscles and motor units in one region of the upper airway are impacted by adjustments in an adjacent airway region. In this case, the focus is on regulation of the expiratory airstream by the larynx and how changes in laryngeal aperture impact muscle motor unit activities downstream in the pharynx. We selected sound production as a framework for study as it requires (i) sustained expiratory airflow, (ii) laryngeal airway regulation for production of whisper and voice, and (iii) pharyngeal airway regulation for production of different vowel sounds. We used these features as the means of manipulating expiratory airflow, pharyngeal, and laryngeal airway opening to compare the effect of each on the activation of genioglossus (GG) muscle motor units in the pharynx. We show that some GG muscle motor units (a) discharge stably on expiration associated with production of vowel sounds, (b) are exquisitely sensitive to subtle alterations in laryngeal airflow, and (c) discharge at higher firing rates in high flow vs. low flow conditions even when producing the same vowel sound. Our results reveal subtle changes in GG motor unit discharge rates that correlate with changes imposed at the larynx, and which may contribute to the regulation of the expiratory airstream.
- Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. J Appl Physiol.
- Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. Journal of Applied Physiology.
- Bailey, E. F. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. SLEEP.
- Bailey, E. F. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. Sleep.
- Kidder, I. J., Mudery, J. A., Barreda, S., Taska, D. J., & Bailey, E. F. (2016). Evaluating the control: minipump implantation and breathing behavior in the neonatal rat. Journal of applied physiology (Bethesda, Md. : 1985), 121(3), 615-22.More infoWe evaluated genioglossus (GG) gross motoneuron morphology, electromyographic (EMG) activities, and respiratory patterning in rat pups allowed to develop without interference (unexposed) and pups born to dams subjected to osmotic minipump implantation in utero (saline-exposed). In experiment 1, 48 Sprague-Dawley rat pups (Charles-River Laboratories), ages postnatal day 7 (P7) through postnatal day 10 (P10), were drawn from two experimental groups, saline-exposed (n = 24) and unexposed (n = 24), and studied on P7, P8, P9, or P10. Pups in both groups were sedated (Inactin hydrate, 70 mg/kg), and fine-wire electrodes were inserted into the GG muscle of the tongue and intercostal muscles to record EMG activities during breathing in air and at three levels of normoxic hypercapnia [inspired CO2 fraction (FiCO2 ): 0.03, 0.06, and 0.09]. Using this approach, we assessed breathing frequency, heart rate, apnea type, respiratory event types, and respiratory stability. In experiment 2, 16 rat pups were drawn from the same experimental groups, saline-exposed (n = 9) and unexposed (n = 7), and used in motoneuron-labeling studies. In these pups a retrograde dye was injected into the GG muscle, and the brain stems were subsequently harvested and sliced. Labeled GG motoneurons were identified with microscopy, impaled, and filled with Lucifer yellow. Double-labeled motoneurons were reconstructed, and the number of primary projections and soma volumes were calculated. Whereas pups in each group exhibited the same number (P = 0.226) and duration (P = 0.093) of respiratory event types and comparable motoneuron morphologies, pups in the implant group exhibited more central apneas and respiratory instability relative to pups allowed to develop without interference.
- Vranish, J. R., & Bailey, E. F. (2016). Inspiratory Muscle Training Improves Sleep and Mitigates Cardiovascular Dysfunction in Obstructive Sleep Apnea. Sleep, 39(6), 1179-85.More infoNew and effective strategies are needed to manage the autonomic and cardiovascular sequelae of obstructive sleep apnea (OSA). We assessed the effect of daily inspiratory muscle strength training (IMT) on sleep and cardiovascular function in adults unable to use continuous positive airway pressure (CPAP) therapy.
- Bailey, E. F. (2015). A comprehensive assessment of genioglossus electromyographic activity in healthy adults..
- Bailey, E. F. (2015). Daily respiratory training with large intrathoracic pressures, but not large lung volumes, lowers blood pressure in normotensive adults..
- Bailey, E. F. (2015). Developmental nicotine exposure adversely effects respiratory patterning in the barbiturate anesthetized neonatal rat..
- Bailey, E. F. (2015). Phonation-related rate coding and recruitment in the genioglossus muscle..
- Barreda, S., Kidder, I. J., Mudery, J. A., & Bailey, E. F. (2015). Developmental nicotine exposure adversely effects respiratory patterning in the barbiturate anesthetized neonatal rat. Respiratory physiology & neurobiology, 208, 45-50.More infoNeonates at risk for sudden infant death syndrome (SIDS) are hospitalized for cardiorespiratory monitoring however, monitoring is costly and generates large quantities of averaged data that serve as poor predictors of infant risk. In this study we used a traditional autocorrelation function (ACF) testing its suitability as a tool to detect subtle alterations in respiratory patterning in vivo. We applied the ACF to chest wall motion tracings obtained from rat pups in the period corresponding to the mid-to-end of the third trimester of human pregnancy. Pups were drawn from two groups: nicotine-exposed and saline-exposed at each age (i.e., P7, P8, P9, and P10). Respiratory-related motions of the chest wall were recorded in room air and in response to an arousal stimulus (FIO2 14%). The autocorrelation function was used to determine measures of breathing rate and respiratory patterning. Unlike alternative tools such as Poincare plots that depict an averaged difference in a measure breath to breath, the ACF when applied to a digitized chest wall trace yields an instantaneous sample of data points that can be used to compare (data) points at the same time in the next breath or in any subsequent number of breaths. The moment-to-moment evaluation of chest wall motion detected subtle differences in respiratory pattern in rat pups exposed to nicotine in utero and aged matched saline-exposed peers. The ACF can be applied online as well as to existing data sets and requires comparatively short sampling windows (∼2 min). As shown here, the ACF could be used to identify factors that precipitate or minimize instability and thus, offers a quantitative measure of risk in vulnerable populations.
- Shumway, K. R., Porfirio, D. J., & Bailey, E. F. (2015). Phonation-related rate coding and recruitment in the genioglossus muscle. Experimental brain research, 233(7), 2133-40.More infoMotor unit recruitment was assessed in two muscles with similar muscle fiber-type compositions and that participate in skilled movements: the tongue muscle, genioglossus (GG), and the hand muscle, first dorsal interosseous (FDI). Our primary objectives were to determine in the framework of a voluntary movement whether muscle force is regulated in tongue as it is in limb, i.e., via processes of rate coding and recruitment. Recruitment in the two muscles was assessed within each subject in the context of ramp force (FDI) and in the tongue (GG) during vowel production and specifically, in the context of ramp increases in loudness, and subsequently expressed relative to the maximal. The principle findings of the study are that the general rules of recruitment and rate coding hold true for both GG and FDI, and second, that average firing rates, firing rates at recruitment and peak firing rates in GG are significantly higher than for FDI (P
- Vranish, J. R., & Bailey, E. F. (2015). A comprehensive assessment of genioglossus electromyographic activity in healthy adults. Journal of neurophysiology, 113(7), 2692-9.More infoThe genioglossus (GG) is an extrinsic muscle of the human tongue that plays a critical role in preserving airway patency. In the last quarter century, >50 studies have reported on respiratory-related GG electromyographic (EMG) activity in human subjects. Remarkably, of the studies performed, none have duplicated subject body position, electrode recording locations, and/or breathing task(s), making interpretation and integration of the results across studies extremely challenging. In addition, more recent research assessing lingual anatomy and muscle contractile properties has identified regional differences in muscle fiber type and myosin heavy chain expression, giving rise to the possibility that the anterior and posterior regions of the muscle fulfill distinct functions. Here, we assessed EMG activity in anterior and posterior regions of the GG, across upright and supine, in rest breathing and in volitionally modulated breathing tasks. We tested the hypotheses that GG EMG is greater in the posterior region and in supine, except when breathing is subject to volitional modulation. Our results show differences in the magnitude of EMG (%regional maximum) between anterior and posterior muscle regions (7.95 ± 0.57 vs. 11.10 ± 0.99, respectively; P < 0.001), and between upright and supine (8.63 ± 0.73 vs. 10.42 ± 0.90, respectively; P = 0.008). Although the nature of a task affects the magnitude of EMG (P < 0.001), the effect is similar for anterior and posterior muscle regions and across upright and supine (P > 0.2).
- Vranish, J. R., & Bailey, E. F. (2015). Daily respiratory training with large intrathoracic pressures, but not large lung volumes, lowers blood pressure in normotensive adults. Respiratory physiology & neurobiology, 216, 63-9.More infoInspiratory muscle training holds promise as a non-pharmacologic treatment that can improve respiratory muscle strength, reduce blood pressure, and improve autonomic balance in hypertensive patients. There is a gap in knowledge regarding the specific respiratory stimulus that gives rise to these favorable outcomes. We implemented five respiratory training protocols that differed in the magnitude and direction of the lung volumes and/or intrathoracic pressures generated by subjects in training. Normotensive adults were randomly assigned to each group and trained daily for 6 weeks. Pre-post and weekly measures of blood pressure showed significant declines in systolic [-8.96 mmHg (95% CI, 7.39-10.53)] and diastolic [-5.25 mmHg (95% CI, 3.67-6.83)] blood pressures for subjects who trained with large positive or negative intrathoracic pressures. Subjects who trained with modest intrathoracic pressures or large lung volumes saw no improvement in blood pressure (P > 0.3). Large intra-thoracic pressures are the specific respiratory stimulus underpinning breathing training related improvements in blood pressure.
- Bailey, E. F. (2014). Neural drive to respiratory muscles in the spontaneously breathing rat pup..
- Kidder, I. J., Mudery, J. A., & Bailey, E. F. (2014). Neural drive to respiratory muscles in the spontaneously breathing rat pup. RESPIRATORY PHYSIOLOGY & NEUROBIOLOGY, 202, 64-70.More infoThe neonatal rodent serves as useful and appropriate model within which to study respiratory system development. Despite an extensive literature that documents respiratory control in vitro, in vivo studies have relied upon whole body plethysmography to determine measures of respiratory frequency and tidal volume. However, plethysmography restricts access to the animal and thus, respiratory muscle electromyographic (EMG) activities have not been recorded in these studies previously. Electromyography yields accurate information about neural respiratory center output to the musculature and therefore, about the control of breathing in the intact animal. In this case, we documented neural drive to respiratory pump and upper airway muscles, electrocardiogram (ECG) and chest wall motions in rat pups up to 10 days of age noting sighs, spontaneous central apneas and hypopneas in room air and with successive increments in fractional inspired CO2 (F1CO2). Our findings underscore the advantages of EMG recordings for purposes of determining the magnitude and distribution of neural drive to respiratory muscles and for characterizing the full range of breathing behaviors exhibited by rats in the early postnatal period. (C) 2014 Elsevier B.V. All rights reserved.
- Kidder, I. J., Mudery, J. A., & Bailey, E. F. (2014). Neural drive to respiratory muscles in the spontaneously breathing rat pup. Respiratory physiology & neurobiology, 202, 64-70.More infoThe neonatal rodent serves as useful and appropriate model within which to study respiratory system development. Despite an extensive literature that documents respiratory control in vitro, in vivo studies have relied upon whole body plethysmography to determine measures of respiratory frequency and tidal volume. However, plethysmography restricts access to the animal and thus, respiratory muscle electromyographic (EMG) activities have not been recorded in these studies previously. Electromyography yields accurate information about neural respiratory center output to the musculature and therefore, about the control of breathing in the intact animal. In this case, we documented neural drive to respiratory pump and upper airway muscles, electrocardiogram (ECG) and chest wall motions in rat pups up to 10 days of age noting sighs, spontaneous central apneas and hypopneas in room air and with successive increments in fractional inspired CO2 (FICO2). Our findings underscore the advantages of EMG recordings for purposes of determining the magnitude and distribution of neural drive to respiratory muscles and for characterizing the full range of breathing behaviors exhibited by rats in the early postnatal period.
- Bailey, E. F. (2013). Human hypoglossal motor unit activities in exercise..
- Walls, C. E., Laine, C. M., Kidder, I. J., & Bailey, E. F. (2013). Human hypoglossal motor unit activities in exercise. The Journal of physiology, 591(14), 3579-90.More infoThe genioglossus (GG) muscle is considered the principal protruder muscle of the tongue that dilates and stiffens the pharyngeal airway. We recorded whole muscle and single motor unit (MU) activities in healthy adults performing progressive intensity exercise on a cycle ergometer. Tungsten microelectrodes were inserted percutaneously into the GG of 11 subjects (20-40 years) to record electromyographic (EMG) activities and pulmonary ventilation (VI) at rest and at workload increments up to 300 W. Increases in respiratory drive were associated with increases in VI, mean inspiratory flow (Vt/Ti) and tonic and phasic components of the GG EMG activity. In contrast, individual MUs typically showed expiration-related decreases in firing as exercise intensity increased. We suggest the decrease in MU activity may occur secondary to afferent feedback from lungs/chest wall and that compensation for more negative inspiratory airway pressures generated during heavy exercise occurs primarily via recruitment of previously silent MUs.
- Bailey, E. F. (2012). Cortical entrainment of human hypoglossal motor unit activities..
- Laine, C. M., Nickerson, L. A., & Bailey, E. F. (2012). Cortical entrainment of human hypoglossal motor unit activities. Journal of neurophysiology, 107(1), 493-9.More infoOutput from the primary motor cortex contains oscillations that can have frequency-specific effects on the firing of motoneurons (MNs). Whereas much is known about the effects of oscillatory cortical drive on the output of spinal MN pools, considerably less is known about the effects on cranial motor nuclei, which govern speech/oromotor control. Here, we investigated cortical input to one such motor pool, the hypoglossal motor nucleus (HMN), which controls muscles of the tongue. We recorded intramuscular genioglossus electromyogram (EMG) and scalp EEG from healthy adult subjects performing a tongue protrusion task. Cortical entrainment of HMN population activity was assessed by measuring coherence between EEG and multiunit EMG activity. In addition, cortical entrainment of individual MN firing activity was assessed by measuring phase locking between single motor unit (SMU) action potentials and EEG oscillations. We found that cortical entrainment of multiunit activity was detectable within the 15- to 40-Hz frequency range but was inconsistent across recordings. By comparison, cortical entrainment of SMU spike timing was reliable within the same frequency range. Furthermore, this effect was found to be intermittent over time. Our study represents an important step in understanding corticomuscular synchronization in the context of human oromotor control and is the first study to document SMU entrainment by cortical oscillations in vivo.
- Bailey, E. F. (2011). Activities of human genioglossus motor units. Respiratory physiology & neurobiology, 179(1), 14-22.More infoUpper airway muscles play an important role in regulating airway lumen and in increasing the ability of the pharynx to remain patent in the face of subatmospheric intraluminal pressures produced during inspiration. Due to the considerable technical challenges associated with recording from muscles of the upper airway, much of the experimental work conducted in human subjects has centered on recording respiratory-related activities of the extrinsic tongue protudor muscle, the genioglossus (GG). The GG is one of eight muscles that invest the human tongue (Abd-El-Malek, 1939). All eight muscles are innervated by the hypoglossal nerve (cranial nerve XII) the cell bodies of which are located in the hypoglossal motor nucleus (HMN) of the caudal medulla. Much of the earlier work on the respiratory-related activity of XII motoneurons was based on recordings obtained from single motor axons dissected from the whole XII nerve or from whole muscle GG EMG recordings. Detailed information regarding respiratory-related GG motor unit activities was lacking until as recently as 2006. This paper examines key findings that have emerged from the last decade of work conducted in human subjects. Wherever appropriate, these results are compared with results obtained from in vitro and in vivo studies conducted in non-human mammals. The review is written with the objective of facilitating some discussion and some new thoughts regarding future research directions. The material is framed around four topics: (a) motor unit type, (b) rate coding and recruitment, (c) motor unit activity patterns, and (d) a compartment based view of pharyngeal airway control.
- Bailey, E. F. (2011). Activities of human genioglossus motor units..
- Bailey, E. F. (2011). Common synaptic input to the human hypoglossal motor nucleus..
- Bailey, E. F. (2011). Respiratory muscles and motoneurons..
- Fregosi, R. F., Bailey, E. F., & Fuller, D. D. (2011). Respiratory muscles and motoneurons. Respiratory physiology & neurobiology, 179(1), 1-2.
- Laine, C. M., & Bailey, E. F. (2011). Common synaptic input to the human hypoglossal motor nucleus. Journal of neurophysiology, 105(1), 380-7.More infoThe tongue plays a key role in various volitional and automatic functions such as swallowing, maintenance of airway patency, and speech. Precisely how hypoglossal motor neurons, which control the tongue, receive and process their often concurrent input drives is a subject of ongoing research. We investigated common synaptic input to the hypoglossal motor nucleus by measuring the coordination of spike timing, firing rate, and oscillatory activity across motor units recorded from unilateral (i.e., within a belly) or bilateral (i.e., across both bellies) locations within the genioglossus (GG), the primary protruder muscle of the tongue. Simultaneously recorded pairs of motor units were obtained from 14 healthy adult volunteers using tungsten microelectrodes inserted percutaneously into the GG while the subjects were engaged in volitional tongue protrusion or rest breathing. Bilateral motor unit pairs showed concurrent low frequency alterations in firing rate (common drive) with no significant difference between tasks. Unilateral motor unit pairs showed significantly stronger common drive in the protrusion task compared with rest breathing, as well as higher indices of synchronous spiking (short-term synchrony). Common oscillatory input was assessed using coherence analysis and was observed in all conditions for frequencies up to ∼ 5 Hz. Coherence at frequencies up to ∼ 10 Hz was strongest in motor unit pairs recorded from the same GG belly in tongue protrusion. Taken together, our results suggest that cortical drive increases motor unit coordination within but not across GG bellies, while input drive during rest breathing is distributed uniformly to both bellies of the muscle.
- Bailey, E. F. (2010). Tonically discharging genioglossus motor units show no evidence of rate coding with hypercapnia..
- Richardson, P. A., & Bailey, E. F. (2010). Tonically discharging genioglossus motor units show no evidence of rate coding with hypercapnia. Journal of neurophysiology, 103(3), 1315-21.More infoThe genioglossus (GG) is considered the principle protrudor muscle of the human tongue. Unlike most skeletal muscles, GG electromyographic (EMG) activities are robustly preserved in sleep and thus may fulfill a critical role in preserving airway patency. Previous studies in human subjects also confirm that the GG EMG increases in response to chemoreceptor and mechanoreceptor stimulation. This increase occurs secondary to the recruitment of previously inactive motor units (MUs) and/or an increase in firing rate of already active MUs. Which strategy the nervous system uses when the synaptic drive onto GG motoneurons increases is not known. Here we report on GG whole muscle and tonic MU activities under conditions that mimic sleep, i.e., mild-moderate elevations in CO(2) (3% inspired CO(2) or the addition of a 1.0 l dead space) and elevated airway resistance. Based on previous work in rat, we hypothesized that mild hypercapnia would increase the firing rates of tonic MUs and that these effects would be further potentiated by a modest increase in airway resistance. Fine wire and tungsten microelectrodes were inserted into the GG to record whole muscle and single MU activities in 21 subjects (13 women, 8 men; 20-55 yr). Either 3% inspired CO(2) or added dead space resulted in a 200-300% increase in the amplitude of both tonic and phasic components of the whole muscle GG EMG and a doubling of minute ventilation. Despite these changes, recordings obtained from a total of 84 tonically discharging GG single MUs provide no evidence of a change in firing rate under any of the conditions. On this basis we conclude that in healthy adults, the increase in the tonic component of the whole muscle GG EMG secondary to mild hypercapnia is due almost exclusively to the recruitment of previously inactive MUs.
- Bailey, E. F. (2009). Genioglossus and intrinsic electromyographic activities in impeded and unimpeded protrusion tasks..
- Pittman, L. J., & Bailey, E. F. (2009). Genioglossus and intrinsic electromyographic activities in impeded and unimpeded protrusion tasks. Journal of neurophysiology, 101(1), 276-82.More infoEight muscles invest the human tongue: four extrinsic muscles have external origins and insert into the tongue body and four intrinsic muscles originate and terminate within the tongue. Previously, we noted minimal activation of the genioglossus tongue muscle during impeded protrusion tasks (i.e., having subjects push the tongue against a force transducer), suggesting that other muscles play a role in the production of tongue force. Accordingly, we sought to characterize genioglossus tongue muscle activities during impeded and unimpeded protrusion tasks (i.e., having subjects slowly and smoothly move the tongue out of their mouth). Electromyographic (EMG) and single motor-unit potentials of the extrinsic genioglossus muscle were recorded with tungsten microelectrodes and EMG activities of intrinsic tongue muscles were recorded with hook-wire electrodes inserted into the anterior tongue body. Tongue position was detected by an isotonic transducer coupled to the tongue tip. Protrusive force was detected by a force transducer attached to a rigid bar. Genioglossus and intrinsic tongue muscles were simultaneously active in both impeded and unimpeded protrusion tasks. Genioglossus whole muscle EMG and single motor-unit activities changed faithfully as a function of tongue position, with increased discharge associated with protrusion and decreased discharge associated with retraction back to the rest position. In contrast, during the impeded protrusion task drive the genioglossus muscle remained constant as protrusion force increased. Conversely, intrinsic tongue muscle activities appropriately followed changes in both tongue position and force. Importantly, we observed significantly higher levels of intrinsic muscle activity in the impeded protrusion task. These observations suggest that protrusion of the human tongue requires activation of the genioglossus and intrinsic protrudor muscles, with the former more important for establishing anterior-posterior tongue location and the latter playing a greater role in the generation of protrusive force. A biomechanical model of these actions is provided and discussed.
- Bailey, E. F. (2008). A tasty morsel: the role of the dorsal vagal complex in the regulation of food intake and swallowing. Focus on "BDNF/TrkB signaling interacts with GABAergic system to inhibit rhythmic swallowing in the rat," by Bariohay et al. American journal of physiology. Regulatory, integrative and comparative physiology, 295(4), R1048-9.
- Bailey, E. F. (2008). A tasty morsel: the role of the dorsal vagal complex in the regulation of food intake and swallowing. Focus on "BDNF/TrkB signaling interacts with GABAergic system to inhibit rhythmic swallowing in the rat," by Bariohay et al..
- Bailey, E. F. (2007). Firing patterns of human genioglossus motor units during voluntary tongue movement..
- Bailey, E. F. (2007). Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction..
- Bailey, E. F. (2007). Sleep/wake firing patterns of human genioglossus motor units..
- Bailey, E. F., Fridel, K. W., & Rice, A. D. (2007). Sleep/wake firing patterns of human genioglossus motor units. Journal of neurophysiology, 98(6), 3284-91.More infoAlthough studies of the principal tongue protrudor muscle genioglossus (GG) suggest that whole muscle GG electromyographic (EMG) activities are preserved in nonrapid eye movement (NREM) sleep, it is unclear what influence sleep exerts on individual GG motor unit (MU) activities. We characterized the firing patterns of human GG MUs in wakefulness and NREM sleep with the aim of determining 1) whether the range of MU discharge patterns evident in wakefulness is preserved in sleep and 2) what effect the removal of the "wakefulness" input has on the magnitude of the respiratory modulation of MU activities. Microelectrodes inserted into the extrinsic tongue protrudor muscle, the genioglossus, were used to follow the discharge of single MUs. We categorized MU activities on the basis of the temporal relationship between the spike train and the respiration cycle and quantified the magnitude of the respiratory modulation of each MU using the eta (eta(2)) index, in wakefulness and sleep. The majority of MUs exhibited subtle increases or decreases in respiratory modulation but were otherwise unaffected by NREM sleep. In contrast, 30% of MUs exhibited marked sleep-associated changes in discharge frequency and respiratory modulation. We suggest that GG MUs should not be considered exclusively tonic or phasic; rather, the discharge pattern appears to be a flexible feature of GG activities in healthy young adults. Whether such flexibility is important in the response to changes in the chemical and/or mechanical environment and whether it is preserved as a function of aging or in individuals with obstructive sleep apnea are critical questions for future research.
- Bailey, E. F., Rice, A. D., & Fuglevand, A. J. (2007). Firing patterns of human genioglossus motor units during voluntary tongue movement. Journal of neurophysiology, 97(1), 933-6.More infoThe tongue participates in a range of complex oromotor behaviors, including mastication, swallowing, respiration, and speech. Previous electromyographic studies of the human tongue have focused on respiratory-related tongue muscle activities and their role in maintaining upper airway patency. Remarkably, the activities of human hypoglossal motor units have not been studied during the execution of voluntary maneuvers. We recorded single motor unit activity using tungsten microelectrodes in the genioglossus muscle of 10 healthy human subjects performing both slow tongue protrusions and a static holding maneuver. Displacement of the tongue was detected by an isotonic transducer coupled to the lingual surface through a customized lever arm. For protrusion trials, the firing rate at recruitment was 13.1 +/- 3 Hz and increased steeply to an average of 24 +/- 6 Hz, often with very modest increases in tongue protrusion. For the static holding task, the average firing rate was 16.1 +/- 4 Hz, which is surprisingly high relative to limb motor units. The average coefficient of variation of interspike intervals was approximately 20% (range, 10-28%). These are the first recordings of their type obtained in human subjects and provide an initial glimpse into the voluntary control of hypoglossal motoneurons during tongue movements presumably instigated by activity in the motor cortex.
- Van Zutphen, C., Janssen, P., Hassan, M., Cabrera, R., Bailey, E. F., & Fregosi, R. F. (2007). Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction. NMR in biomedicine, 20(7), 682-91.More infoThe velopharynx is the most collapsible segment of the upper airway in patients with obstructive sleep apnea. However, we do not know if velopharyngeal compliance is uniform throughout its length, or if compliance is modified by contraction of upper airway muscles. We tested the hypothesis that rostral and caudal velopharyngeal (VP) compliance differs, and that tongue muscle contraction reduces compliance. High-resolution MR images of the VP were made at nasopharyngeal pressures ranging from -9 to 9 cmH(2)O in anesthetized rats. Images were obtained twice at each pressure, once with and once without bilateral hypoglossal nerve stimulation. The volume of the caudal and rostral VP was computed at each pressure. The caudal VP was significantly (P = 0.0058) more compliant than the rostral VP, but electrical stimulation of the tongue muscles did not change compliance. VP critical pressure (Pcrit; pressure at zero airway volume) averaged -25.2 and -12.1 cmH(2)O in the rostral and caudal VP, respectively (P < 0.0001). Coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone dilated the VP and made Pcrit more negative (P < 0.0001), but only in the caudal VP. In the rat, the caudal VP is more collapsible than the rostral VP, and either coactivation of tongue protrudor and retractor muscles or contraction of protrudor muscles alone makes this region more difficult to close. Thus, tongue muscle contraction protects the caudal VP, which appears to be a particularly vulnerable segment of the nasopharyngeal airway. With suitable modification, the methods described here, including tongue muscle stimulation at different pharyngeal pressures, may be appropriate for experiments in human subjects.
- Bailey, E. F. (2006). Anatomic consequences of intrinsic tongue muscle activation..
- Bailey, E. F. (2006). Modulation of upper airway muscle activities by bronchopulmonary afferents..
- Bailey, E. F., & Fregosi, R. F. (2006). Modulation of upper airway muscle activities by bronchopulmonary afferents. Journal of applied physiology (Bethesda, Md. : 1985), 101(2), 609-17.More infoHere we review the influence of bronchopulmonary receptors (slowly and rapidly adapting pulmonary stretch receptors, and pulmonary/bronchial C-fiber receptors) on respiratory-related motor output to upper airway muscles acting on the larynx, tongue, and hyoid arch. Review of the literature shows that all muscles in all three regions are profoundly inhibited by lung inflation, which excites slowly adapting pulmonary stretch receptors. This widespread coactivation includes the recruitment of muscles that have opposing mechanical actions, suggesting that the stiffness of upper airway muscles is highly regulated. A profound lack of information on the modulation of upper airway muscles by rapidly adapting receptors and bronchopulmonary C-fiber receptors prohibits formulation of a conclusive opinion as to their actions and underscores an urgent need for new studies in this area. The preponderance of the data support the view that discharge arising in slowly adapting pulmonary stretch receptors plays an important role in the initiation of the widespread and highly coordinated recruitment of laryngeal, tongue, and hyoid muscles during airway obstruction.
- Bailey, E. F., Huang, Y., & Fregosi, R. F. (2006). Anatomic consequences of intrinsic tongue muscle activation. Journal of applied physiology (Bethesda, Md. : 1985), 101(5), 1377-85.More infoWe recently showed respiratory-related coactivation of both extrinsic and intrinsic tongue muscles in the rat. Here, we test the hypothesis that intrinsic tongue muscles contribute importantly to changes in velopharyngeal airway volume. Spontaneously breathing anesthetized rats were placed in a MRI scanner. A catheter was placed in the hypopharynx and connected to a pressure source. Axial and sagittal images of the velopharyngeal airway were obtained, and the volume of each image was computed at airway pressures ranging from +5.0 to -5.0 cm H2O. We obtained images in the hypoglossal intact animal (i.e., coactivation of intrinsic and extrinsic tongue muscles) and after selective denervation of the intrinsic tongue muscles, with and without electrical stimulation. Denervation of the intrinsic tongue muscles reduced velopharyngeal airway volume at atmospheric and positive airway pressures. Electrical stimulation of the intact hypoglossal nerve increased velopharyngeal airway volume; however, when stimulation was repeated after selective denervation of the intrinsic tongue muscles, the increase in velopharyngeal airway volume was significantly attenuated. These findings support our working hypothesis that intrinsic tongue muscles play a critical role in modulating upper airway patency.
- Bailey, E. F. (2005). PO2-dependent changes in intrinsic and extrinsic tongue muscle activities in the rat..
- Bailey, E. F. (2005). Respiratory-related discharge of genioglossus muscle motor units..
- Bailey, E. F., Janssen, P. L., & Fregosi, R. F. (2005). PO2-dependent changes in intrinsic and extrinsic tongue muscle activities in the rat. American journal of respiratory and critical care medicine, 171(12), 1403-7.More infoHistorically, respiratory-related research in sleep apnea has focused exclusively on the extrinsic tongue muscles (i.e., genioglossus, hyoglossus, and styloglossus). Until recently, the respiratory control and function of intrinsic tongue muscles (i.e., inferior and superior longitudinalis, transverses, and verticalis), which comprise the bulk of the tongue, were unknown.
- John, J., Bailey, E. F., & Fregosi, R. F. (2005). Respiratory-related discharge of genioglossus muscle motor units. American journal of respiratory and critical care medicine, 172(10), 1331-7.More infoLittle is known about the respiratory-related discharge properties of motor units driving any of the eight muscles that control the movement, shape, and stiffness of the mammalian tongue.
- Bailey, E. F. (2004). Coordination of intrinsic and extrinsic tongue muscles during spontaneous breathing in the rat..
- Bailey, E. F., & Fregosi, R. F. (2004). Coordination of intrinsic and extrinsic tongue muscles during spontaneous breathing in the rat. Journal of applied physiology (Bethesda, Md. : 1985), 96(2), 440-9.More infoThe muscular-hydrostat model of tongue function proposes a constant interaction of extrinsic (external bony attachment, insertion into base of tongue) and intrinsic (origin and insertion within the tongue) tongue muscles in all tongue movements (Kier WM and Smith KK. Zool J Linn Soc 83: 207-324, 1985). Yet, research that examines the respiratory-related effects of tongue function in mammals continues to focus almost exclusively on the respiratory control and function of the extrinsic tongue protrusor muscle, the genioglossus muscle. The respiratory control and function of the intrinsic tongue muscles are unknown. Our purpose was to determine whether intrinsic tongue muscles have a respiration-related activity pattern and whether intrinsic tongue muscles are coactivated with extrinsic tongue muscles in response to respiratory-related sensory stimuli. Esophageal pressure and electromyographic (EMG) activity of an extrinsic tongue muscle (hyoglossus), an intrinsic tongue muscle (superior longitudinal), and an external intercostal muscle were studied in anesthetized, tracheotomized, spontaneously breathing rats. Mean inspiratory EMG activity was compared at five levels of inspired CO2. Intrinsic tongue muscles were often quiescent during eupnea but active during hypercapnia, whereas extrinsic tongue muscles were active in both eupnea and hypercapnia. During hypercapnia, the activities of the airway muscles were largely coincident, although the onset of extrinsic muscle activity generally preceded the onset of intrinsic muscle activation. Our findings provide evidence, in an in vivo rodent preparation, of respiratory modulation of motoneurons supplying intrinsic tongue muscles. Distinctions noted between intrinsic and extrinsic activities could be due to differences in motoneuron properties or the central, respiration-related control of each motoneuron population.
- Bailey, E. F. (2003). Pressure-volume behaviour of the rat upper airway: effects of tongue muscle activation..
- Bailey, E. F., & Fregosi, R. F. (2003). Pressure-volume behaviour of the rat upper airway: effects of tongue muscle activation. The Journal of physiology, 548(Pt 2), 563-8.More infoOur hypothesis was that the simultaneous activation of tongue protrudor and retractor muscles (co-activation) would constrict and stiffen the pharyngeal airway more than the independent activation of tongue protrudor muscles. Upper airway stiffness was determined by injecting known volumes of air into the sealed pharyngeal airway of the anaesthetized rat while measuring nasal pressure under control (no-stimulus) and stimulus conditions (volume paired with hypoglossal (XII) nerve stimulation). Stimulation of the whole XII nerves (co-activation) or the medial XII branches (protrudor activation) effected similar increases in total pharyngeal airway stiffness. Importantly, co-activation produced volume compression (airway narrowing) at large airway volumes (P < 0.05), but had no effect on airway dimension at low airway volumes. In comparison, protrudor activation resulted in significant volume expansion (airway dilatation) at low airway volumes and airway narrowing at high airway volumes (P < 0.05). In conclusion, both co-activation and independent protrudor muscle activation increase airway stiffness. However, their effects on airway size are complex and depend on the condition of the airway at the time of activation.
- Bailey, E. F. (2002). Speaking and breathing in high respiratory drive..
- Bailey, E. F., & Hoit, J. D. (2002). Speaking and breathing in high respiratory drive. Journal of speech, language, and hearing research : JSLHR, 45(1), 89-99.More infoPulmonary ventilation during speech breathing reflects the sum of the airflow changes used to speak and to meet the metabolic needs of the body. Studying interactions between speaking and breathing may provide insights into the mechanisms of shared respiratory control. The purposes of this study were to determine if healthy subjects exhibit task-specific breathing behaviors in high respiratory drive and to document subjects' perceptions during breathing and speaking under these conditions. Ten men were studied in air and high CO2. Magnetometers were used to estimate lung volume, rib cage and abdomen volumes, minute volume, breathing frequency, tidal volume, inspiratory and expiratory duration, and inspiratory and expiratory flow. Subjects' perceptions were assessed informally. Results indicated that the chest wall kinematic behaviors associated with breathing and speaking in high drive were similar in pattern but differed in the magnitudes of lung volume and rib cage volume events and in inspiratory and expiratory flow. Linguistic influences remained strong, but not as strong as under normal conditions. All subjects reported a heightened sense of breathing-related discomfort during speaking as opposed to breathing in high respiratory drive. We conclude that in healthy subjects breathing behavior associated with speaking in high respiratory drive is guided continuously by shared linguistic and metabolic influences. A parallel-processing model is proposed to explain the behaviors observed.
- Bailey, E. F. (2001). Effect of pulmonary stretch receptor feedback and CO(2) on upper airway and respiratory pump muscle activity in the rat..
- Bailey, E. F., Jones, C. L., Reeder, J. C., Fuller, D. D., & Fregosi, R. F. (2001). Effect of pulmonary stretch receptor feedback and CO(2) on upper airway and respiratory pump muscle activity in the rat. The Journal of physiology, 532(Pt 2), 525-34.More info1. Our purpose was to examine the effects of chemoreceptor stimulation and lung inflation on neural drive to tongue protrudor and retractor muscles in the rat. 2. Inspiratory flow, tidal volume, transpulmonary pressure, compliance and electromyographic (EMG) activity of genioglossus (GG), hyoglossus (HG) and inspiratory intercostal (IIC) muscles were studied in 11 anaesthetized, tracheotomized and spontaneously breathing rats. Mean EMG activity during inspiration was compared with mean EMG activity during an occluded inspiration, at each of five levels of inspired CO(2) (0, 3, 6, 9 and 12 %). 3. Lung inflation suppressed EMG activity in all muscles, with the effect on both tongue muscles exceeding that of the intercostal muscles. Static elevations of end-expiratory lung volume evoked by 2 cmH(2)O positive end-expiratory pressure (PEEP) had no effect on tongue muscle activity. 4. Despite increasing inspiratory flow, tidal volume and transpulmonary pressure, the inhibition of tongue muscle activity by lung inflation diminished as arterial PCO2 (P(a),CO(2)) increased. 5. The onset of tongue muscle activity relative to the onset of IIC muscle activity advanced with increases in P(a),CO(2) but was unaffected by lung inflation. This suggests that hypoglossal and external intercostal motoneuron pools are controlled by different circuits or have different sensitivities to CO(2), lung inflation and/or anaesthetic agents. 6. We conclude that hypoglossal motoneuronal activity is more strongly influenced by chemoreceptor-mediated facilitation than by lung volume-mediated inhibition. Hypoglossal motoneurons driving tongue protrudor and retractor muscles respond identically to these stimuli.
- Bailey, E. F., LaCross, A., & Watson, P. J. (2014, March). Genioglossus muscle motor unit activity during static vowel articulation. Motor Speech Conference. Sarasota, FL: Madonna Rehabilitation Hospital.