A Comparison of Lingual Pressure Generation Measures Using Two Devices in Community-Dwelling, Typically Aging Adults: An Important Clinical Implication.

DESIGN: A multisite, prospective, and randomized within-subject design study. SETTING: Five university settings in varied geographical areas in the United States. PURPOSE: The purpose of this study was to compare lingual pressure generation using the Tongueometer (TO) and the Iowa Oral Performance Instrument (IOPI) in typically aging, community-dwelling adults during three measurement tasks: maximum isometric pressure (MIP), regular effort saliva swallow (RESS) pressure, and effortful saliva swallow pressure (ESP). PARTICIPANTS: Eighty-seven typically aging, community-dwelling adults (aged 55 years and over) with no self-reported history of swallowing or neurological disorders were recruited to complete this study. RESULTS: Strong positive associations were found between the lingual pressure generation measures from the TO and IOPI in all tasks in typically aging adults, with Pearson correlations ranging from r = .780 to .874, p < .001. Agreement between the devices (Lin's concordance correlation coefficient) ranged from moderate for the MIP (ρc = .78) and ESP (ρc = .61) tasks to weak agreement for the RESS task (ρc = .47). MIP, RESS pressure, and ESP were lower when measured by the TO compared with the IOPI, p < .001. CONCLUSIONS: The TO measures lingual pressure generation similarly to the IOPI but pressures register lower when using the TO than the IOPI in typically aging persons. This supports the need for developing normative values specific to the TO device or development of a valid and reliable conversion formula from TO to IOPI normative values. At this time, the clinical use of reference values from the TO should not be generalized to IOPI normative values.

Flexibility for Intensity Dosing in Lingual Resistance Exercises: A Large Randomized Clinical Trial in Typically Aging Adults as Proof of Principle.

OBJECTIVE: The objective of this study was to determine the effect of intensity dosing during tongue exercise on tongue pressure generation, adherence, and perceived effort. DESIGN: This was a five-site, prospective, randomized clinical trial. Outcome measures were obtained across multiple baselines, biweekly during exercise, and 4-weeks post-intervention. SETTING: The general community at each study site. PARTICIPANTS: Typically aging adults between 55-82 years of age with no history of neurological or swallowing disorders. Eighty-four volunteers completed the study. INTERVENTIONS: Participants were randomly assigned to one of four exercise groups: (a) maximum intensity/no biofeedback, (b) progressive intensity/no biofeedback, (c) maximum intensity/biofeedback, and (d) progressive intensity/biofeedback. Half of the participants completed a maintenance exercise program. OUTCOME MEASURES: Maximum isometric pressure (MIP), regular effort saliva swallow pressure, adherence, and the Borg Rating of Perceived Exertion Scale. RESULTS: All exercise protocols were efficacious for gains in MIP (large effect sizes; Cohen's d). Group 3 made gains in regular effort saliva swallow pressure (medium effect size). There was a significant change in perceived exertion for regular effort saliva swallow pressure at 8 weeks. Tongue pressure gains were maintained at 1 month, regardless of maintenance group status. Mean adherence across groups was high. CONCLUSIONS: All groups improved pressure generation. Intensity dosing differences did not affect strength gains, adherence, or detraining. Regular effort saliva swallow pressure may be most responsive to maximum intensity with biofeedback. The findings suggest flexibility in approach to tongue exercise protocols. Tongue muscles may differ from limb muscles in terms of dose response and neuroplasticity principles.

The Effect of Genetic Taste Status on Swallowing: A Literature Review.

PURPOSE: Swallowing and taste share innervation pathways and are crucial to nutritive intake. Individuals vary in their perception of taste due to factors such as genetics; however, it is unclear to what extent genetic taste status influences swallowing physiology and function. The purpose of this review article is to provide background on genetic taste status, review the evidence on the association between genetic taste status and swallowing, and discuss research and clinical implications. METHOD: A comprehensive literature review was conducted using search terms related to swallowing and genetic taste status. Studies were included if they investigated the main effect of genetic taste status on swallowing or the interaction of genetic taste status with other variables. Studies were grouped by participant population (healthy participants or persons with a swallowing disorder), swallowing-related outcome measure, and method of genetic taste status measurement. RESULTS: The results were mixed, with five of 10 reviewed studies reporting a statistically significant main or interaction effect on swallowing. Most studies included healthy participants, with only one study investigating participants with dysphagia. Additionally, swallowing-related outcome measures and methods of determining genetic taste status varied greatly between studies conducted on separate cohorts. CONCLUSIONS: Few studies have incorporated genetic taste status as a variable in swallowing research, and results are mixed. Future research on sensation and swallowing should consider the potential effect of genetic taste status and follow standardized procedures for its determination. Despite the limited evidence, clinicians may consider how individual differences in perception shape swallowing outcomes.

The Effect of Swallowing Cues in Healthy Individuals: An Exploratory Study.

The goal of this study was to determine whether providing verbal and visual cues about swallowing changes the timing of swallowing events, and whether this information interacts with bolus volume. 20 healthy adults swallowed 5 ml and 15 ml liquid barium mixed with orange juice under videofluoroscopy during 2 conditions: one condition absent swallowing-specific cues and one condition with verbal and visual input about the swallowing process. Outcome measures included the timing of 10 swallowing events and the number of swallows per bolus. As expected, volume had a significant effect on all outcome measures (p < 0.05). Three timing events differed by cueing condition: 1. swallowing reaction time was earlier for control (- 9.45 ms vs. - 2.01 ms, p = 0.033); 2. the time between initial hyoid movement and maximum hyoid elevation was longer for control (152.85 ms vs. 143.79 ms; p = 0.015); and 3. the onset of upper esophageal sphincter opening occurred later after bolus entry into the pharynx for the swallowing cues condition (111.9 ms vs. 103.31 ms; p = 0.017); however, effect sizes were small (< 0.2). There was a significant interaction between cue condition and bolus volume on swallowing frequency, such that the mean number of swallows of 15 ml boluses was slightly higher during the control condition than during the swallowing cues condition. There were no significant interactions on measures of timing, suggesting distinct mechanisms for the effect of bolus volume and cues on swallowing kinematics. Further research is needed to investigate the effects of different cue modalities and focus (internal vs. external) on swallowing physiology.

The Feasibility of Home-Based Treatment Using Vibratory Stimulation in Chronic Severe Dysphagia.

PURPOSE: Previously, externally placed vibratory laryngeal stimulation increased rates of swallowing in persons with and without dysphagia. This study examined the feasibility of using a vibratory device on the skin over the thyroid cartilage for home-based swallowing rehabilitation in long-standing dysphagia. METHOD: Only participants with long-standing dysphagia (> 6 months) following cerebrovascular accident or head/neck cancer who had not previously benefited from dysphagia therapy participated. The device had two modes used daily for 90 days. In automatic mode, participants wore the device when awake, which vibrated for 4-8 s every 5 min to trigger a volitional swallow. In manual mode, participants practiced by activating vibration while swallowing rapidly. Study-related adverse events, such as pneumonia, and device-recorded adherence were tracked. Swallowing function on a modified barium swallow study was assessed at baseline and after 3 months of device use. Outcome measures included the Dysphagia Outcome and Severity Scale (DOSS), Penetration-Aspiration Scale (PAS), and swallowing timing measures. Participants' perceptions of the vibratory device and training were obtained. RESULTS: The intent to treat analysis showed seven of 11 participants completed the study, all with severe chronic dysphagia. Of those seven participants completing the study, two developed respiratory complications (possibly due to pneumonia) that cleared after antibiotic intervention. For prescribed practice trials, adherence was 80% or greater in four of seven participants (57%) whereas prescribed automatic stimulations were met in only two of seven participants (29%). Three participants (43%) had a modest benefit on DOSS. The time to vestibule closure after the bolus passed the ramus was reduced in five participants (71%) on the modified barium swallow study. CONCLUSION: Overall, the results have indicated that intensive home-based practice with stimulation may provide limited functional benefits in severe chronic dysphagia. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.21498591.

The effect of taste on swallowing: A scoping and systematic review.

Consuming foods and liquids for nutrition requires the coordination of several muscles. Swallowing is triggered and modified by sensory inputs from the aerodigestive tract. Taste has recently received attention as a potential modulator of swallowing physiology, function, and neural activation; additionally, taste impairment is a sequela of COVID-19. This review presents factors impacting taste and swallowing, systematically summarizes the existing literature, and assesses the quality of included studies. A search was conducted for original research including taste stimulation, deglutition-related measure(s), and human participants. Study design, independent and dependent variables, and participant characteristics were coded; included studies were assessed for quality and risk of bias. Forty-eight articles were included after abstract and full-text review. Synthesis was complicated by variable sensory components of stimuli (taste category and intensity, pure taste vs. flavor, chemesthesis, volume/amount, consistency, temperature), participant characteristics, confounding variables such as genetic taster status, and methods of measurement. Most studies had a high risk of at least one type of bias and were of fair or poor quality. Interpretation is limited by wide variability in methods, taste stimulation, confounding factors, and lower-quality evidence. Existing studies suggest that taste can modulate swallowing, but more rigorous and standardized research is needed.

Dysphagia in Myositis: A Study of the Structural and Physiologic Changes Resulting in Disordered Swallowing.

OBJECTIVES: Dysphagia in patients with myositis is associated with an increased risk of aspiration pneumonia. However, the pathophysiology of dysphagia is poorly understood. The aim of this study was to understand how myositis affects swallowing physiology on videofluoroscopic swallow study. DESIGN: This is a retrospective review of video fluoroscopic swallowing studies on 23 myositis patients with dysphagia from 2011 to 2016. Swallow studies were analyzed by timing of swallowing events and duration of swallowing events, diameter of upper esophageal sphincter opening, Modified Barium Swallow Impairment Profile, and Penetration-Aspiration Scale. The outcome measures for patients were compared with an archived videofluoroscopic swallow study from healthy, age-matched participants by Wilcoxon rank-sum tests. RESULTS: Patients with myositis had a shorter duration of upper esophageal sphincter opening (P < 0.0001) and laryngeal vestibule closure (P < 0.0001) than healthy subjects. The diameter of upper esophageal sphincter opening did not differ between groups. Patients with myositis presented with higher scores on the MBSIMP than healthy subjects, indicating great impairment particularly during the pharyngeal phase of swallowing, and a higher frequency of penetration and aspiration. CONCLUSIONS: Dysphagia in patients with myositis may be attributed to reduced endurance of swallowing musculature rather than mechanical obstruction of the upper esophageal sphincter.

Swallow Screen Associated With Airway Protection and Dysphagia After Acute Stroke.

OBJECTIVE: The goal was to examine the outcomes of an existing swallow screen protocol in comparison to results from a formal videofluoroscopic protocol. DESIGN: Prospective cohort study. SETTING: Acute hospital. PARTICIPANTS: Patients after acute stroke (N=48). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: The Johns Hopkins Hospital Brain Rescue Unit 3 oz Swallow Screen was implemented by nursing staff upon admission. Videofluoroscopy was conducted within 72 hours of diagnostic neuroimaging and initial swallow screen. Predictive values of the bedside swallow screen (pass/fail) for clinical judgment of dysphagia on videofluoroscopy (presence/absence) were calculated. Overall impairment scores from the Modified Barium Swallowing Impairment Profile were analyzed with respect to swallow screen results. RESULTS: Thirteen participants failed the swallow screen, and 35 passed. Of the 35 patients who passed the swallow screen, 15 were clinically diagnosed with dysphagia on videofluoroscopy. Although pass/fail of the swallow screen was not a significant predictor of presence/absence of dysphagia, a logistic regression model including components of Laryngeal Elevation, Laryngeal Vestibule Closure, and Anterior Hyoid Excursion, and sex was statistically significant for swallow screen outcome. CONCLUSION: The results of this study suggest that a swallow screen of aspiration risk can identify patients with the most need for videofluoroscopic evaluation and dysphagia management. Additionally, patients who fail a swallow screen are more likely to present with physiologic impairments related to airway protection on videofluoroscopy.

The Association of 3-D Volume and 2-D Area of Post-swallow Pharyngeal Residue on CT Imaging.

Pharyngeal residue, the material that remains in the pharynx after swallowing, is an important marker of impairments in swallowing and prandial aspiration risk. The goals of this study were to determine whether the 2D area of post-swallow residue accurately represents its 3D volume, and if the laterality of residue would affect this association. Thirteen patients with dysphagia due to brainstem stroke completed dynamic 320-detector row computed tomography while swallowing a trial of 10 ml honey-thick barium. 3D volumes of pharyngeal residue were compared to 2D lateral and anterior-posterior areas, and a laterality index for residue location was computed. Although the anteroposterior area of residue was larger than the lateral area, the two measures were positively correlated with one another and with residue volume. On separate bivariate regression analyses, residue volume was accurately predicted by both lateral (R2 = 0.91) and anteroposterior (R2 = 0.88) residue areas, with limited incidence of high residuals. Half of the sample demonstrated a majority of pharyngeal residue lateralized to one side of the pharynx, with no effect of laterality on the association between areas and volume. In conclusion, the area of post-swallow pharyngeal residue was associated with volume, with limitations in specific cases. Direct measurement of pharyngeal residue volume and swallowing physiology with 3D-CT can be used to validate results from standard 2D instrumentation.

Do Ratings of Swallowing Function Differ by Videofluoroscopic Rate? An Exploratory Analysis in Patients After Acute Stroke.

OBJECTIVE: To determine differences between continuous videofluoroscopic swallow studies (VFSS) with a pulse rate and frame rate of 30 and the same swallows reduced to 15 frames per second (fps) on measures of swallowing function in patients after acute ischemic stroke. DESIGN: Blinded comparison. SETTING: Acute hospital. PARTICIPANTS: Patients after ischemic stroke (N=20). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Single and sequential sips of thin liquids, single sips of nectar liquids, pudding, and cookie boluses were rated on measures of timing of swallowing events, Modified Barium Swallowing Impairment Profile component scores, and Penetration-Aspiration Scale scores. The ratings for videos at 15 fps and 30 fps were compared by Wilcoxon signed rank tests. RESULTS: Pharyngeal transit time was longer and bolus entry into the hypopharynx was later for 30 fps than for 15 fps. Components of Oral Residue and Pharyngoesophageal Segment Opening ratings were more severe for 15 fps than 30 fps, whereas Bolus Transport and Initiation of Pharyngeal Swallow were rated as more severe for 30 fps than for 15 fps. There was no difference between 30 fps and 15 fps on the remaining measures, including Penetration-Aspiration Scale scores. CONCLUSION: Continuous VFSS recorded at 30 fps and their down-sampled 15 fps duplicates yielded contrasting results on certain durational and functional measures of swallowing, though not on others. VFSS should be administered continuously or at 30 pulses per second for valid assessment of swallowing while using other methods to reduce radiation exposure.

Swallowing Changes in Community-Dwelling Older Adults.

Older adults may evidence changes in swallowing physiology. Our goals were to identify dysphagia risk in community-dwelling older adults with no history of dysphagia, and to compare swallowing physiology and safety between older and younger adults. Thirty-two older adults with no history of dysphagia were prospectively recruited and completed the Dysphagia Handicap Index (DHI), two trials of a 3 oz. swallow screen, and videofluoroscopy (VFSS). Self-ratings of swallowing function were compared to published norms by paired t tests, and multivariate logistic regression models were generated to determine whether these ratings and VFSS analysis of swallowing function were associated with failure of one or both swallow screen trials. Archived VFSS of 33 younger adults were compared to older adults with Wilcoxon rank-sum tests. The DHI scores of older adults were higher than published non-dysphagic adults but lower than dysphagic adults. Older participants with greater Oral Residue scores were more likely to fail both swallow screen trials. Older adults received higher median MBSImP™© scores for select pharyngeal components than younger adults. The two age groups did not differ on Penetration-Aspiration Scale scores, and no aspiration was observed. Measures of swallowing in older individuals may reflect age-related sensory and motor changes in the context of functional swallowing and adequate airway protection.

Neural Mechanisms of Swallowing Dysfunction and Apraxia of Speech in Acute Stroke.

Speech and swallowing utilize overlapping anatomy and are thus inherently related processes. We sought to identify common neural mechanisms between risk of swallowing dysfunction and apraxia of speech (AOS). This was a retrospective analysis using data from a prospectively collected cohort. Left hemisphere stroke patients (68 subjects) tested with the Apraxia Battery for Adults II, a swallow screen, and MRI were included in the study. Main outcome measure was the presence of AOS or aspiration risk after stroke. We identified a significant association between AOS measures and increased aspiration risk (defined by failed swallow screen; p = 0.04; OR 5.2). Lesions in pars opercularis of Broca's area (BA 44) were associated with both AOS (p = 0.044; OR 9.7) and increased aspiration risk (p = 0.04; OR 5) but deficits rarely co-occurred in the same cases. Lesions in left premotor cortex (BA 6) were not significantly associated with increased aspiration risk (p = 0.06; OR 3.3) but were significantly associated with AOS (p = 0.008; OR 7). Impaired swallowing function was also associated with lesions in Wernicke's area (BA 22; p = 0.05; OR 3.5) and pars triangularis (BA 45; p = 0.02; OR 6.8). AOS and risk of aspiration are associated in patients with acute left hemisphere stroke. Acute infarct in the pars opercularis of Broca's area is associated with both deficits, though they rarely co-occur in the same individual. The co-occurrence of AOS and risk of aspiration likely reflects dependence on closely related neural structures.

The physiology of oral whistling: a combined radiographic and MRI analysis.

The fluid mechanics of whistling involve the instability of an air jet, resultant vortex rings, and the interaction of these rings with rigid boundaries (see http://www.canal-u.tv/video/cerimes/etude_radiocinematographique_d_un_siffleur_turc_de_kuskoy.13056 and Meyer J. Whistled Languages. Berlin, Germany: Springer, 2015, p. 74-774). Experimental models support the hypothesis that the sound in human whistling is generated by a Helmholtz resonator, suggesting that the oral cavity acts as a resonant chamber bounded by two orifices, posteriorly by raising the tongue to the hard palate, and anteriorly by pursed lips (Henrywood RH, Agarwal A. Phys Fluids 25: 107101, 2013). However, the detailed anatomical changes in the vocal tract and their relation to the frequencies generated have not been described in the literature. In this study, videofluoroscopic and simultaneous audio recordings were made of subjects whistling with the bilabial (i.e., "puckered lip") technique. One whistling subject was also recorded, using magnetic resonance imaging. As predicted by theory, the frequency of sound generated decreased as the size of the resonant cavity increased; this relationship was preserved throughout various whistling tasks and was consistent across subjects. Changes in the size of the resonant cavity were primarily modulated by tongue position rather than jaw opening and closing. Additionally, when high-frequency notes were produced, lateral chambers formed in the buccal space. These results provide the first dynamic anatomical evidence concerning the acoustic production of human whistling. NEW & NOTEWORTHY We establish a new and much firmer quantitative and physiological footing to current theoretical models on human whistling. We also document a novel lateral airflow mechanism used by both of our participants to produce high-frequency notes.

Timing of cortical activation during spontaneous swallowing.

Saliva accumulation in the oropharynx generates an automatic pattern of swallowing in the brainstem in animals. Previous fMRI studies have found that spontaneous saliva and water swallows in humans evoked activation following swallow onset in both precentral motor and postcentral somatosensory cortical regions. Using event-related averaging of continuous functional near infrared spectroscopy (fNIRS), we examined cortical hemodynamic responses (HDR) from 5 s before to 35 s after spontaneous reflexive saliva swallow onset in the lateral postcentral somatosensory and precentral motor regions in both hemispheres in healthy volunteers. Three HDR changes from baseline were detected. First, the onset of HDR occurred 2 s before swallow onset in the left postcentral somatosensory area and 0.67 s before swallow onset in the right postcentral somatosensory area. Second, an early HDR peak amplitude occurred 3-4 s after swallow onset in all four regions. Z scores relative to baseline pre-swallow cortical activity levels averaged 20 and 22.7 s in the right and left somatosensory regions and 10 and 15.8 s in left and right motor areas, respectively. Finally, a late HDR peak occurring between 22 and 23 s after swallow onset in the somatosensory regions and 17-19 s in the motor areas likely resulted from esophageal peristalsis. Overall, cortical activation timing relative to swallow onsets showed activation began before the pharyngeal phase of swallowing in the somatosensory areas. This indicates that somatosensory triggering of swallowing occurs not only in the brainstem but also in the cortex for reflexive saliva swallowing in awake humans.

Taste Perception and Water Swallow Screen Results in Old-Old Women.

Changes in both swallowing and taste commonly occur in advanced age, though the relationship between the two is unknown. This study examined the association between a water swallow screen test and taste identification and intensity rating. Participants included 47 community-dwelling women aged 85-94 years. Participants completed three trials of a water swallow screen and were observed for signs of aspiration, which, if present, indicated failure. Four pure taste stimuli at low and high concentrations and water were presented, and participants selected one of five taste labels and rated their intensity on the generalized Labeled Magnitude Scale. Ratios of intensity ratings were computed for each taste stimulus to compare the perception of low and high concentrations. The association between water swallow screen failure, correct taste identification, and taste intensity ratio was evaluated with logistic regression modeling, with mediating factors of frailty and number of comorbidities. Failure of three water swallow screen trials was associated with a higher taste intensity ratio for caffeine (bitter) and a lower taste intensity ratio for sucrose (sweet). Correct identification of taste, frailty, and number of comorbidities were not associated with failure of any number of water swallow screen trials. Intensity ratings of certain tastes may be associated with swallowing in old-old women. Heightened vigilance in this population may be necessary to prevent complications related to dietary intake.

Vibration over the larynx increases swallowing and cortical activation for swallowing.

Sensory input can alter swallowing control in both the cortex and brainstem. Electrical stimulation of superior laryngeal nerve afferents increases reflexive swallowing in animals, with different frequencies optimally effective across species. Here we determined 1) if neck vibration overlying the larynx affected the fundamental frequency of the voice demonstrating penetration of vibration into the laryngeal tissues, and 2) if vibration, in comparison with sham, increased spontaneous swallowing and enhanced cortical hemodynamic responses to swallows in the swallowing network. A device with two motors, one over each thyroid lamina, delivered intermittent 10-s epochs of vibration. We recorded swallows and event-related changes in blood oxygenation level to swallows over the motor and sensory swallowing cortexes bilaterally using functional near infrared spectroscopy. Ten healthy participants completed eight 20-min conditions in counterbalanced order with either epochs of continuous vibration at 30, 70, 110, 150, and 70 + 110 Hz combined, 4-Hz pulsed vibration at 70 + 110 Hz, or two sham conditions without stimulation. Stimulation epochs were separated by interstimulus intervals varying between 30 and 45 s in duration. Vibration significantly reduced the fundamental frequency of the voice compared with no stimulation demonstrating that vibration penetrated laryngeal tissues. Vibration at 70 and at 150 Hz increased spontaneous swallowing compared with sham. Hemodynamic responses to swallows in the motor cortex were enhanced during conditions containing stimulation compared with sham. As vibratory stimulation on the neck increased spontaneous swallowing and enhanced cortical activation for swallows in healthy participants, it may be useful for enhancing swallowing in patients with dysphagia.NEW & NOTEWORTHY Vibratory stimulation at 70 and 150 Hz on the neck overlying the larynx increased the frequency of spontaneous swallowing. Simultaneously vibration also enhanced hemodynamic responses in the motor cortex to swallows when recorded with functional near-infrared spectroscopy (fNIRS). As vibrotactile stimulation on the neck enhanced cortical activation for swallowing in healthy participants, it may be useful for enhancing swallowing in patients with dysphagia.

Sour taste increases swallowing and prolongs hemodynamic responses in the cortical swallowing network.

Sour stimuli have been shown to upregulate swallowing in patients and in healthy volunteers. However, such changes may be dependent on taste-induced increases in salivary flow. Other mechanisms include genetic taster status (Bartoshuk LM, Duffy VB, Green BG, Hoffman HJ, Ko CW, Lucchina LA, Weiffenbach JM. Physiol Behav 82: 109-114, 2004) and differences between sour and other tastes. We investigated the effects of taste on swallowing frequency and cortical activation in the swallowing network and whether taster status affected responses. Three-milliliter boluses of sour, sour with slow infusion, sweet, water, and water with infusion were compared on swallowing frequency and hemodynamic responses. The sour conditions increased swallowing frequency, whereas sweet and water did not. Changes in cortical oxygenated hemoglobin (hemodynamic responses) measured by functional near-infrared spectroscopy were averaged over 30 trials for each condition per participant in the right and left motor cortex, S1 and supplementary motor area for 30 s following bolus onset. Motion artifact in the hemodynamic response occurred 0-2 s after bolus onset, when the majority of swallows occurred. The peak hemodynamic response 2-7 s after bolus onset did not differ by taste, hemisphere, or cortical location. The mean hemodynamic response 17-22 s after bolus onset was highest in the motor regions of both hemispheres, and greater in the sour and infusion condition than in the water condition. Genetic taster status did not alter changes in swallowing frequency or hemodynamic response. As sour taste significantly increased swallowing and cortical activation equally with and without slow infusion, increases in the cortical swallowing were due to sour taste.

Using devices to upregulate nonnutritive swallowing in typically developing infants.

The role of various sensory stimuli for stimulating swallowing in infants may be of importance for assisting infants to develop oral feeding. We evaluated the swallowing mechanism response to two devices for increasing the rate of nonnutritive swallowing in two typically developing infant age groups, ages 2-4 mo and 7-9 mo. One device was a pacifier familiar to the infant; the other was a small vibrator placed on the skin overlying the thyroid cartilage. The rate of nonnutritive swallowing while infants were awake was compared in three 10-min conditions: at rest without stimulation (spontaneous); during nonnutritive sucking with a pacifier; and over 10 min containing 18 epochs of vibratory stimulation for 10 s each. To assess whether vibration on the throat over the laryngeal area altered respiration, the mean cycle length was compared between 10-min intervals either containing vibratory stimulation or without stimulation at rest. Both the pacifier and laryngeal vibration stimulation doubled the rate of swallowing in the infants with a mean age of 3 mo 16 days and infants with a mean age of 8 mo 8 days. No differences occurred in the mean respiratory cycle length between intervals with and without vibration in either age group. Results suggest that nonnutritive sucking, vibration, or both might be beneficial in enhancing swallowing in young infants. Because vibration on the neck would not interfere with oral transfer of liquid, it might provide additional stimulation for swallowing during oral feeding. Both stimulation types should be evaluated for enhancing swallowing in infants with immature swallowing skills.