Steven M. Barlow

Synthetic orocutaneous stimulation entrains preterm infants with feeding difficulties to suck

Background:Prematurity can disrupt the development of a specialized neural circuit known as suck central pattern generator (sCPG), which often leads to poor feeding skills. The extent to which suck can be entrained using a synthetically patterned orocutaneous input to promote its development in preterm infants who lack a functional suck is unknown.Objective:To evaluate the effects of a new motorized ‘pulsating’ pacifier capable of entraining the sCPG in tube-fed premature infants who lack a functional suck and exhibit feeding disorders.Methods:Prospective cohort study of 31 preterm infants assigned to either the oral patterned entrainment intervention (study) or non-treated (controls) group, matched by gestational age, birth weight, oxygen supplementation history and oral feed status. Study infants received a daily regimen of orocutaneous pulse trains through a pneumatically controlled silicone pacifier concurrent with gavage feeds.Results:The patterned orocutaneous stimulus was highly effective in accelerating the development of non-nutritive suck (NNS) in preterm infants. A repeated-measure multivariate analysis of covariance revealed significant increases in minute rates for total oral compressions, NNS bursts, and NNS cycles, suck cycles per burst, and the ratiometric measure of NNS cycles as a percentage of total ororhythmic output. Moreover, study infants also manifest significantly greater success at achieving oral feeds, surpassing their control counterparts by a factor of 3.1 × (72.8% daily oral feed versus 23.3% daily oral feed, respectively).Conclusion:Functional expression of the sCPG among preterm infants who lack an organized suck can be induced through the delivery of synthetically patterned orocutaneous pulse trains. The rapid emergence of NNS in treated infants is accompanied by a significant increase in the proportion of nutrient taken orally.

Oral and respiratory control for preterm feeding

Purpose of reviewFeeding competency is a frequent and serious challenge to the neonatal intensive care unit survivors and to the physician–provider–parent teams. The urgency of effective assessment and intervention techniques is obviated to promote safe swallow, as attainment of oral feeding for the preterm infant/newborn is one of the prerequisites for hospital discharge. If left unresolved, feeding problems may persist into early childhood and may require management by pediatric gastroenterologists and feeding therapists. This review highlights studies aimed at understanding the motor control and development of nonnutritive and nutritive suck, swallow, and coordination with respiration in preterm populations. Recent findingsFunctional linkages between suck–swallow and swallow–respiration manifest transitional forms during late gestation and can be delayed or modified by sensory experience and/or disease processes. Moreover, brainstem central pattern generator (CPG) networks and their neuromuscular targets attain functional status at different rates, which ultimately influences cross-system interactions among individual CPGs. Entrainment of trigeminal primary afferents to activate the suck CPG is one example of a clinical intervention to prime cross-system interactions among ororhythmic pattern generating networks in the preterm and term infants. SummaryThe genesis of within-system CPG control for rate and amplitude scaling matures differentially for suck, mastication, swallow, and respiration. Cross-system interactions among these CPGs represent targets of opportunity for new interventions that optimize experience-dependent mechanisms to promote robust ororhythmic patterning and safe swallows among preterm infants.

Mechanical frequency detection thresholds in the human face

Afferent information originating from mechanoreceptors located within perioral facial skin is considered to play an important role in the development and maintenance of fine motor skill associated with the production of speech. To date, little quantitative information is available on the frequency sensitivity of the face to controlled sinusoidal displacements, especially in areas of tissue that change shape during speech. The purpose was to determine the mechanical frequency detection thresholds of select skin sites in the face and hand using a psychophysical procedure. Mean frequency detection thresholds for all facial skin sites were significantly higher than thresholds for the forefinger. Further, pacinian-type frequency sensitivity, characteristic of the finger, was absent in the face. Finally, vibratory stimuli may be useful in the assessment of skin sense in patients with suspected involvement of the trigeminal system. A case study is presented to highlight the quantitative nature of this psychophysical procedure.

Central pattern generation involved in oral and respiratory control for feeding in the term infant

Purpose of reviewDrinking and eating are essential skills for survival and benefit from the coordination of several pattern generating networks and their musculoskeletal effectors to achieve safe swallows. Oralpharyngoesophageal motility develops during infancy and early childhood, and is influenced by various factors, including neuromuscular maturation, dietary and postural habits, arousal state, ongoing illnesses, congenital anomalies, and the effects of medical or surgical interventions. Gastroesophageal reflux is frequent in neonates and infants, and its role in neonatal morbidity including dysphagia, chronic lung disease, or apparent life-threatening events is not well understood. This review highlights recent studies aimed at understanding the development of oral feeding skills, and cross-system interactions among the brainstem, spinal, and cerebral networks involved in feeding. Recent findingsFunctional linkages between suck–swallow and swallow–respiration manifest transitional forms during late gestation through the first year of life, which can be delayed or modified by sensory experience or disease processes, or both. Relevant central pattern generator (CPG) networks and their neuromuscular targets attain functional status at different rates, which ultimately influences cross-system CPG interactions. Entrainment of trigeminal primary afferents accelerates pattern genesis for the suck CPG and transition-to-oral feed in the RDS preterm infant. SummaryThe genesis of within-system CPG control for rate and amplitude scaling matures differentially for suck, mastication, swallow, and respiration. Cross-system interactions among these CPGs represent targets of opportunity for new interventions, which optimize experience-dependent mechanisms to promote safe swallows among newborn and pediatric patients.

Intrinsic dynamics and mechanosensory modulation of non-nutritive sucking in human infants

The human infant is endowed with a complex mechanism for the ingestion of nutrients that becomes functional in late fetal life. The sucking motor pattern is generally accepted to be under the control of pattern generating circuitry located in the brainstem reticular formation. Systems under the control of a central pattern generator (CPG) may use afferent feedback to allow for changing environmental conditions. Although it is clear that afferent pathways serving the orofacial region become responsive to mechanical stimulation early in fetal life, little is known about the integration of afferent information into the suck CPG. The actifier, a device for the mechanical stimulation of intraoral and perioral tissues, was designed and used to investigate the response properties of the human infant suck CPG to patterned mechanical stimulation. Sinusoid and square waveform stimuli elicited responses including modulation of jaw kinematics and synchronization [entrainment] of non-nutritive suck motor patterns to the mechanical stimulus. These data provide evidence that the suck CPG is responsive to mechanical stimulation of perioral and intraoral soft tissues.

Vocal tract aerodynamics during syllable productions: Normative data and theoretical implications

Summary Estimates of subglottal air pressure and mean volume velocity of air flow were recorded from 30 normal adults during repetition of consonant-vowel syllables. There were no gender differences in subglottal air pressure, and men used significantly higher flows than women did in all speaking tasks. Women had greater laryngeal airway resistances than men did for [i] vowels. Women also had greater resistances during [i] vowels than during [ a ] vowels, and the men did not. Separate norms are presented for men and women for use in aerodynamic examination of dysphonic subjects.

Laryngeal somatosensory deficits in Parkinson's disease: implications for speech respiratory and phonatory control

Parkinson’s disease (PD) is often associated with substantial impairment of speech respiratory and phonatory control. However, the degree to which these impairments are related to abnormal laryngeal sensory function is unknown. This study examined whether individuals with PD exhibited abnormal and more asymmetric laryngeal somatosensory function compared with healthy controls, and whether these deficits were associated with disease and voice severity. Nineteen PD participants were tested and compared with 18 healthy controls. Testing included endoscopic assessment of laryngeal somatosensory function, with aerodynamic and acoustic assessment of respiratory and phonatory control, and clinical ratings of voice and disease severity. PD participants exhibited significantly abnormal and asymmetric laryngeal somatosensory function compared with healthy controls. Sensory deficits were significantly associated with timing of phonatory onset, voice intensity, respiratory driving pressure, laryngeal resistance, lung volume expended per syllable, disease severity, and voice severity. These results suggest that respiratory and phonatory control are influenced by laryngeal somatosensory function, that speech-related deficits in PD are related to abnormal laryngeal somatosensory function, and that this function may degrade as a function of disease severity. Thus, PD may represent a model of airway sensorimotor disintegration, highlighting the important role of the basal ganglia and related neural networks in the integration of laryngeal sensory input for speech-related motor control.

Functional Outcomes of Cleft Lip Surgery. Part I: Study Design and Surgeon Ratings of Lip Disability and Need for Lip Revision

Objective: Children with a cleft of the upper lip exhibit obvious facial disfigurement. Many require multiple lip surgeries for an optimal esthetic result. However, because the decision for lip revision is based on subjective clinical criteria, clinicians may disagree on whether these surgeries should be performed. To establish more reliable, functionally relevant outcome criteria for evaluation and treatment planning, a clinical trial currently is in progress. In this article, the design of the clinical trial is described and results of a study on subjective evaluations of facial form by surgeons for or against the need for lip revision surgery are presented. Design: Parallel, three-group, nonrandomized clinical trial and subjective evaluations/ratings of facial views by surgeons. Subjects: For the clinical trial, children with repaired cleft lip and palate scheduled for a secondary lip revision, children with repaired cleft lip and palate who did not have lip revision, and noncleft children. For the subjective evaluations, surgeons’ facial ratings of 21 children with repaired cleft lip. Analysis: Descriptive and Kappa statistics assessing the concordance of surgeons’ ratings of (a) repeated facial views and (b) a recommendation of revision on viewing the prerevision and postrevision views. Results: The surgeons’ consistency in rating repeated views was moderate to excellent; however, agreement among the surgeons when rating individual participants was low to moderate. Conclusions: The findings suggest that the agreement among surgeons was poor and support the need for more objective measures to assess the need for revision surgery.

Transitional properties of the mechanically evoked perioral reflex from infancy through adulthood

The organization of motor responses in the orbicularis oris muscle following the delivery of punctate mechanical inputs to vermilion skin of the lips was studied in a group of young infants, school-age children, and adults during periods of voluntary lip muscle activation. A specially designed multi-point array skin contactor, coupled to a position-servo controlled linear motor, was highly effective in driving the early component of the perioral reflex (R1). Overall, the evoked R1 response obtained from the infant was of variable amplitude relative to the children and adults, lacked response specificity, and occurred at a longer latency. This brainstem mediated sensorimotor action appears to take on several characteristics of the adult form by the age of 12. The emergence and maturation of mechanically evoked perioral reflexes is discussed in relation to the acquisition of motor skills, including speech and smiling.

Factors influencing neural activity in parabrachial regions during cat vocalizations

SummaryThe parabrachial nucleus in mammals is intimately connected with other vocalization controlling brainstem structures. It, along with ventromedially adjacent structures, also has been identified as the pneumotaxic center, and as such shows strong respiratory related activity in the anesthetized cat. The current study examines the neuronal activity in cat parabrachial regions during production of instrumentally conditioned vocalizations. Most of the units in our sample show considerable activity during periods between vocalizations. For many units, firing rate fluctuates during the respiratory cycle, although apparently not as strongly as reported in the decerebrate cat. Also, there is often strong phasic activity during periods where animals are licking to ingest their food rewards. During the peri-vocalization period, various neural activity patterns can be recorded. Most common is an activity increase during the vocalization itself. Moreover, in some units, this activity increase has an auditory component. A smaller number of units show other activity patterns, including a suppression of activity during vocalization and activity increases preceding the vocalization. Overall, our results suggest that the parabrachial regions involvement in vocal control is quite complex, involving convergence of respiratory, acoustic, vocalization-related, and perhaps somatosensory influences.