Volitional Swallowing Research Articles

The effect and mechanism of motor imagery based on action observation treatment on dysphagia in Wallenberg Syndrome: a randomized controlled trial.

The effect of motor imagery applied to dysphagia patients with Wallenberg syndrome has not yet been reported. This trial aimed to investigate the effect and mechanism of motor imagery based on action observation treatment in the rehabilitation of patients with dysphagia in Wallenberg syndrome. A randomized controlled trial. The setting was in-patient. Thirty patients with dysphagia of Wallenberg syndrome. The patients were divided into the experimental group and the control group. Both groups received conventional dysphagia treatment, and the experimental group underwent the addition of motor imagery based on action observation treatment to the control group once a day for 14 days. Overall swallowing function was assessed with specific scales before and after intervention. Meanwhile, the functional near infrared spectroscopy was used to detect changes in cerebral hemodynamics during the execution of volitional swallowing task and swallowing motor imagery. The standardized swallowing assessment score (P=0.030), Murray secretion scale score (P=0.044) and swallowing quality of life score (P=0.011) of the experimental group improved better than those of the control group. In addition, multiple brain regions of the cortical presented extensive activation (P<0.05) during the execution of swallowing motor imagery. Moreover, there were significant differences (P<0.05) in brain regions pre-motor and supplementary motor cortex, right primary motor cortex, and right primary somatosensory cortex of the experimental group before and after treatment. The present study indicated that motor imagery based on action observation treatment could improve swallowing function for patients with dysphagia of Wallenberg syndrome as an add-on training. As a top-down rehabilitation training, the mechanism of this therapy may be related to the selective activation of mirror neuron system. Motor imagery based on action observation treatment can be implemented as part of the therapeutic for dysphagia of Wallenberg syndrome.

Hemodynamic signal changes during volitional swallowing in dysphagia patients with different unilateral hemispheric stroke and brainstem stroke: A near-infrared spectroscopy study

Background and objectivesStrokes will result in decreased in cortical excitability and changed in the balance between the affected and unaffected hemispheres. Previous studies have focused on cortical changes in healthy subjects during swallowing, while they remain unknown in patients with stroke at different locations. Thus, the purpose of this study was to research cortical activation patterns of swallowing in patients with dysphagia and healthy subjects by the functional near-infrared spectroscopy (fNIRS). We also focus on the comparability of brain activation areas associated with swallowing between patients with different stroke locations and healthy subjects. Methodstotal of 104 participants were invited to our study, involving 86 patients with dysphagic unilateral hemispheric stroke and 18 age and sex matched healthy controls. The stroke patients were categorized into patients with left unilateral stroke lesions (n = 30), patients with right unilateral stroke lesions (n = 32) and patients with brainstem injury (n = 24) according to different stroke sites. All patients underwent a series of clinical swallowing function assessments, such as the Fiberoptic endoscopic dysphagia severity scale (FEDSS), penetration-aspiration scale (PAS) of Rosenbek, the gugging swallowing screen (GUSS) and the functional oral Intake scale (FOIS) after informed consent has been signed. All participants received the fNIRS system assessment. ResultsThe results showed that extensive areas of the cerebral cortex activated during the swallowing tasks in healthy participants (P < FDR 0.05). For patients with left unilateral stroke lesions, the HbO concentration were strongest over the right hemisphere (P < FDR 0.05). In addition, a less severe activation was also observed in the left hemisphere. Comparable to patients with left unilateral stroke lesions, the strongest activation during swallowing task were found in the left hemisphere in patients with right unilateral stroke lesions (P < FDR 0.05). Similarly, the right hemisphere also has activated less. In contrast, patients with brain stem injury showed more bilaterally activation patterns. ConclusionOur finding states that cortical activation areas differ between patients with different stroke locations and healthy subjects during swallowing. There was a more bilateral activation in healthy participants and patients with lesions in the brainstem while more cortical activation in unaffected hemisphere in patients with unilateral hemispheric stroke. It also provides a basis for the future treatment of dysphagia after stroke.

The Importance of Looking at the REST of the Swallow in Patients With Head and Neck Cancer

Purpose: The swallowing continuum is highly complex and interrelated and has both upstream and downstream implications for volitional swallowing behaviors, anatomic and physiologic impairments, and interventions. Pathologic reflux can cause a plethora of upstream anatomic and physiologic changes in the swallow with associated consequences. Although pathologic reflux can occur in isolation, there is a high incidence of both pathologic reflux and esophageal pathology in patients with head and neck cancer. Along with their known oropharyngeal dysfunction that can evolve over time posttreatment and cause downstream effects in the swallowing continuum, pathologic reflux and esophageal pathology can cause upstream effects, further complicating the interplay and contributing to the overall swallowing impairment. Conclusions: The entire swallowing continuum should be evaluated with videofluoroscopy at yearly intervals in patients with head and neck cancer so that the multidisciplinary dysphagia team understands the interplay, which informs best interventions. The Robust Esophageal Screening Test (REST) is a standardized, validated esophageal screening protocol that can be implemented during the videofluoroscopic swallowing study to better identify potential esophageal pathology, which can be of complex etiology in this population. Results of a recent quality improvement project implementing REST protocol with patients with head and neck cancer found significant esophageal pathology and enhanced team collaborations and decision making for optimal patient care (Gregor &amp; Watts, 2022).

Hemodynamic signal changes and functional connectivity in acute stroke patients with dysphagia during volitional swallowing: a pilot study.

Dysphagia is one of the major post-stroke complications, understanding post-stroke changes in cortical excitability and promoting early remodeling of swallowing-related cortical areas to enable accurate treatment is essential for recovery of patients. We aimed to investigate hemodynamic signal changes and functional connectivity in acute stroke patients with dysphagia compared to age-matched healthy participants in response to volitional swallowing using functional near-infrared spectroscopy (fNIRS) in this pilot study. Patients with first-ever post-stroke dysphagia having an onset of 1-4 weeks and age-matched right-handed healthy subjects were recruited in our study. fNIRS with 47 channels was utilized to detect the oxyhemoglobin (HbO2 ) and reduced hemoglobin (HbR) concentration changes when volitional swallowing. Cohort analysis was performed by a one-sample t-test. Two-sample t-test was utilized to compare the difference in cortical activation between patients with post-stroke dysphagia and healthy subjects. Furthermore, the relative changes in the concentration of the HbO2 throughout the experimental procedure were extracted for the functional connectivity analysis. The Pearson correlation coefficients of the HbO2 concentration of each channel were analyzed on a time series, and then a Fisher Z transformation was then performed, and the transformed values were defined as the functional connection strengths between the channels. In this present study, a total of nine patients with acute post-stroke dysphagia were enrolled in the patient group and nine age-matched healthy participants in the healthy control group. Our study observed that the extensive regions of the cerebral cortex were activated in the healthy control group, while the activation area of patient group's cortical regions was quite limited. The mean functional connectivity strength of participants was 0.485 ± 0.105 in the healthy control group, and 0.252 ± 0.146 in the patient group, with a significant difference between the two groups (p = 0.001). Compared to the healthy individuals, cerebral cortex regions of acute stroke patients were only marginally activated during volitional swallowing task, and the average functional connectivity strength of cortical network in patients was relatively weaker.

Effects of the GABA(B) agonist baclofen on volitional swallowing in normal subjects.

The GABA(B) receptor agonist baclofen is known to suppress the rate of spontaneous swallowing but not pharyngeal muscle contraction. The extent to which baclofen may alter volitional swallowing is not currently known. We investigated the effects of baclofen in healthy subjects, hypothesizing that baclofen exposure would alter volume-regulation and/or piecemeal deglutition behaviors during volitional swallowing attempts. Pharyngeal high-resolution manometry impedance (P-HRM-I) protocol was used to assess swallowing function of 22 healthy adult volunteers (median 29 years) who were investigated on two occasions, receiving 40 mg baclofen (oral) 1 h before study, or placebo (randomized). Standard swallow function variables recommended by the pharyngeal HRM Working Group were derived for 5ml, 10ml, and 20 ml volumes of thin and extremely thick liquid challenges. Multiple swallow behaviors, comprising two swallows <5s apart, were characterized. The spontaneous swallow rate was also determined. Baclofen exposure had no overall significant effect on swallow variables. Upper esophageal sphincter pressure was weaker during exposure to baclofen, during both the pre-deglutitive and post-deglutitive phases of the swallow (p < 0.05 during thick liquid swallows). Piecemeal swallows, where the bolus is separated in two potions, were significantly more common during 20 ml boluses (p=0.002). Baclofen decreased the frequency of piecemeal deglutition overall. Baclofen has limited to no effect on volitional swallowing measures, however, does reduce the likelihood of initiation of piecemeal deglutition to large volume challenges.

Pharyngeal Pressure Variability During Volitional Swallowing Maneuvers.

Within-individual pharyngeal swallowing pressure variability differs among pharyngeal regions in healthy individuals and increases with age. It remains unknown if pharyngeal pressure variability is impacted by volitional swallowing tasks. We hypothesized that pressure variability would increase during volitional swallowing maneuvers and differ among pharyngeal regions depending on the type of swallowing task being performed. Pharyngeal high-resolution manometry was used to record swallowing pressure data from 156 healthy participants during liquid (5 cc) or saliva swallows, and during volitional swallowing tasks including effortful swallow, Mendelsohn maneuver, Masako maneuver, or during postural adjustments. The coefficient of variation was used to determine pressure variability of velopharynx, tongue base, hypopharynx, and upper esophageal sphincter regions. Repeated-measures analysis of variance was used on log-transformed data to examine effects of pharyngeal region and swallowing tasks on swallow-to-swallow variability. There was a significant main effect of task with greater pressure variability for the effortful swallow (p = .002), Mendelsohn maneuver (p < .001), Masako maneuver (p = .002), and the head turn (p = .006) compared with normal effort swallowing. There was also a significant main effect of region (p < .01). In general, swallowing pressure variability was lower for the tongue base and upper esophageal sphincter regions than the hypopharynx. There was no significant interaction of task and region (effortful, p = .182; Mendelsohn, p = .365; Masako, p = .885; chin tuck, p = .840; head turn, p = .059; and inverted, p = .773). Pharyngeal swallowing pressure variability increases in healthy individuals during volitional swallowing tasks. Less stable swallow patterns may result when tasks are less automatic and greater in complexity. These findings may have relevance to swallowing motor control integrity in healthy aging and individuals with neurogenic dysphagia.

Repetitive Transcranial Magnetic Stimulation on the Supplementary Motor Area Changes Brain Connectivity in Functional Dysphagia.

Background: Previous studies arguing that functional dysphagia could be explained by underlying neurobiological mechanisms are insufficient to explain brain regions that functionally interact in patients with functional dysphagia. Therefore, we investigated functional connectivity changes associated with functional dysphagia after applying facilitatory repetitive transcranial magnetic stimulation (rTMS) on the supplementary motor area (SMA). Materials and Methods: A patient with severe long-lasting functional dysphagia and 15 healthy controls participated in this study. A facilitatory 5 Hz rTMS protocol was applied to the patient's SMA. We performed functional magnetic resonance imaging (fMRI) using volitional swallowing tasks to investigate neural network changes before rTMS (pre-rTMS), immediately after rTMS, and 3 months later. Results: The pre-rTMS fMRI results of the patient showed extensive overactivation in the left-lateralized regions related to volitional swallowing compared with the healthy controls. Following rTMS, dysphagia symptoms partially improved. The patient showed positive connectivity with the bilateral cerebellum in the bilateral SMA seeds before rTMS treatment. Furthermore, left-lateralized overactivation was washed out immediately after completion of rTMS, and connectivity between the left SMA and left precentral gyrus recovered 3 months after rTMS treatment. Conclusion: Our findings confirm that functional dysphagia might be a neurobiological manifestation caused by maladaptive functional connectivity changes in brain structures related to swallowing. Furthermore, noninvasive brain modulation with rTMS over the SMA may facilitate functional connectivity changes between the cortical and subcortical regions. Accordingly, these changes will allow control of the movements related to swallowing and may lead to improved clinical symptoms.

Pharyngeal Swallowing During Wake and Sleep.

Sleep is associated with stages of relative cortical quiescence, enabling evaluation of swallowing under periods of reduced consciousness and, hence, absent volition. The aim of this study was to measure and characterize changes in the characteristics of pharyngeal swallows during sleep and wake using high-resolution manometry (HRM). Pharyngeal swallows were recorded with a ManoScan™ HRM in wake-upright, wake-supine, and sleep conditions in 20 healthy participants (mean 27years; range 21-52). Velopharyngeal and hypopharyngeal segments were analysed separately. Contractile integral, mean peak pressure, inverse velocity of superior-to-inferior pharyngeal pressure, and time to first maximum pressure were analysed with custom-designed software. The supine-wake condition was compared to both upright-wake and sleep conditions using linear mixed effects models. No significant differences were found between supine-wake and upright-wake conditions on any measures. The mean peak pharyngeal pressure was lower during sleep than during the supine-wake condition for both the velopharynx (- 60mmHg, standard error [SE] = 11, p < 0.001) and hypopharynx (- 59mmHg, SE = 9, p = 0.001), as was the pharyngeal inverse velocity (- 12ms/cm, SE = 4, p = 0.012) for the hypopharyngeal segment and the pharyngeal contractile integral (- 32mmHg scm, SE = 6, p < 0.001). No significant differences were found in time to the first pharyngeal maximum pressure. This study used HRM to characterize and compare pharyngeal pressures during swallowing in both wake and sleep conditions. No differences were found between upright and supine awake conditions, a finding important to pharyngeal manometric measures made during supine positioning, such as in fMRI. Higher pressures and longer time-related measures of volitional pharyngeal swallowing when awake indicate that cortical input plays an important role in modulation of pharyngeal swallowing.

P 66 Transcranial DC stimulation enhances recovery of swallowing function after stroke – a randomized clinical and MEG trial

Introduction Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation tool that has shown some potential to aid motor rehabilitation following stroke. In the present clinical and neuroimaging study we evaluated whether tDCS is able to speed up the recovery of swallowing function in acute dysphagic stroke patients. Besides relating clinical effects with neuroplastic changes in cortical swallowing processing we aimed to identify factors influencing treatment success. Material and methods In this single-center, double-blind, randomized study (NCT01970384), 60 acute dysphagic stroke patients received anodal tDCS (20 min, 1 mA) or sham stimulation over the contralesional swallowing motor cortex on four consecutive days. If the patient’s condition allowed it, swallowing exercises were performed during stimulation. Swallowing function was thoroughly assessed before and after the study intervention using the Fiberoptic Endoscopic Dysphagia Severity Scale (FEDSS), the dysphagia limit swallow test and two clinical scores, the Dysphagia Severity Rating Scale (DSR) and the Functional Oral Intake Scale (FOIS). In 15 patients, cortical swallowing-associated activation could be recorded during a volitional swallowing task applying 270-channel whole-head MEG before and after the treatment intervention. Results 59 patients completed the study. One patient suffered from recurrent stroke during the study period and was therefore excluded. Study groups did not differ according to demographic data or stroke characteristics. Time from admission to study intervention was 116 h in mean in both groups. Baseline FEDSS, FOIS, DSR and dysphagia limit were comparable. Following stimulation, patients from the treatment group showed significantly greater improvement in FEDSS (1.3 vs 0.4 points, p When looking for indicators of treatment success in the stimulation group only, there was a trend towards a greater improvement of all assessed swallowing scores with early treatment initiation (p Discussion According to our clinical and neurophysiological data, application of tDCS over the contralesional swallowing motor cortex supports cortical swallowing network reorganization, thereby leading to faster rehabilitation of acute post stroke dysphagia. The positive effect was independent of patient age and stroke characteristics, suggesting tDCS as a suitable treatment option for a broad patient population. Early treatment initiation within the suspected time window of maximum neuroplasticity after stroke seems to be beneficial.

Characterization of pharyngeal peristaltic pressure variability during volitional swallowing in healthy individuals.

Recent technological advances incorporated in high resolution manometry have justifiably heightened interest in manometric evaluation of the pharynx. Despite this interest, from both physiologic and clinical perspective there remain a number of unanswered questions regarding the magnitude of variability of pharyngeal pressure phenomena. Therefore, the aim of the present study was to characterize in healthy individuals the inter-subject and recording-site specific variability of pharyngeal peristaltic pressure phenomena. We studied 32 healthy subjects (age: 21-83years,20 under 35years) during dry,5 and 10mL water swallows ×3. Pharyngeal peristaltic pressures were recorded using a high resolution (HR) manometric system and a catheter assembly with 36 circumferential sensors spaced at 1cm intervals positioned trans-nasally to traverse the pharynx, UES and proximal esophagus. Both site-specific pressure data and the Pharyngeal contractile integral (PhCI) showed wide dispersion ranging between values under 50mm Hg to over 300mm Hg and 100-600mm Hg/cm/s,respectively. There was also wide range of dispersion of data for both the standard deviations and the coefficient of variation for all sites (P=.001). The coefficient of variation for PhCI ranged between 0.02 and 0.25 representing data dispersion of 2-25 percent of the mean among subjects (P=.001). Position, age and volume of swallowed fluid did not influence the magnitude of variability. Deglutitive Pharyngeal peristalsis generates pressures with significant degree of site-related and inter-subject variability. This variability is not influenced by age, position and volume of swallowed fluid.

Effect of transcranial direct current stimulation on swallowing apraxia and cortical excitability in stroke patients

Background: Swallowing apraxia is characterized by impaired volitional swallowing but relatively preserved reflexive swallowing. Few studies are available on the effectiveness of behavioral therapy and management of the condition.Objective: This study aimed to investigate the effect of transcranial direct current stimulation (tDCS) on swallowing apraxia and cortical activation in stroke patients.Methods: The study included three inpatients (age 48–70 years; 1 male, 2 females; duration of stroke, 35–55 d) with post-stroke swallowing apraxia and six age-matched healthy subjects (age 45–65 years; 3 males, 3 females). Treatments were divided into two phases: Phase A and Phase B. During Phase A, the inpatients received three weeks of sham tDCS and conventional treatments. During Phase B, these patients received three weeks of anodal tDCS over the bilateral primary sensorimotor cortex (S1M1) of swallowing and conventional treatments. Swallowing apraxia assessments were measured in three inpatients before Phase A, before Phase B, and after Phase B. The electroencephalography (EEG) nonlinear index of approximate entropy (ApEn) was calculated for three patients and six healthy subjects.Results: After tDCS, scores of swallowing apraxia assessments increased, and ApEn indices increased in both stimulated and non-stimulated areas.Conclusions: Anodal tDCS might provide a useful means for recovering swallowing apraxia, and the recovery could be related to increased excitability of the swallowing cortex. Further investigations should explore the relationship between lesion size and/or lesion site and the prognosis of swallowing apraxia.Clinical trial registry: http://www.chictr.org Registration Number: ChiCTR-TRC-14004955

Nonspecific effects of gap paradigm on swallowing

ObjectiveAnalogous to the gap paradigm in experiments for saccadic eye movements with very short reaction times, we hypothesized that the initiation of oropharyngeal swallowing movements guided by visual cues are encouraged under experimental conditions using a similar gap paradigm. MethodsA red visual cue indicating to hold a bolus in the mouth and a blue one indicating to swallow the bolus were sequentially provided on a computer display to 11 healthy participants. The gap period between these cues varied from 0 to 800ms. Swallowing kinetics and kinematics were recorded using surface electromyography and a laser displacement sensor, respectively. ResultsIn comparison with the no-gap paradigm, the delay from the onset of muscle activities to initiation of movement significantly decreased with a 100- (p<0.01) and 200-ms (p<0.005) gap period. With other gap periods, no significant change was detected in the delay. ConclusionsInitiation of visually guided swallowing was enhanced by a gap paradigm of 100–200ms. Wrist flexion was boosted in a similar manner. Thus, the gap effect may be a generalized warning effect. SignificanceOur findings might provide insights into the contribution of the basal ganglia to volitional swallowing.

Behavioural and neurophysiological disruption of corticobulbar motor systems and their effects on sequential pharyngeal swallowing

Primary motor networks are known to be involved in the control of voluntary oral movements as well as the modulation of pharyngeal movements during experimentally controlled single swallows performed on command. The role of these networks in the more typical task of sequential swallowing remains unexplored. This study evaluated the hypothesis that experimental disruption of motor cortical activation would reduce the rate and regularity of repeatedly performed volitional or volitionally initiated motor tasks controlled by corticospinal (finger tapping) and corticobulbar (eyebrow movement, jaw opening, volitional sequential swallowing) motor systems, but would not influence a more reflexive corticobulbar task (reflexive sequential swallowing to pharyngeal water infusion). This premise was investigated in 24 healthy participants using two techniques: a dual task paradigm and a transcranial magnetic stimulation paradigm. Disruption effects were quantified by changes in rate and regularity of performance for each tested motor task. In summary, volitional motor tasks controlled by corticospinal motor networks (finger tapping) are more susceptible to behavioural and neurophysiological disruption than tasks controlled by cortiobulbar motor networks containing a reflexive component (both volitional and experimentally initiated consecutive swallowing). Purely volitional motor tasks controlled by the corticobulbar motor system (eyebrow raising or jaw opening) were affected in similar ways as the volitional corticospinal motor tasks. In summary, tasks involving sequential pharyngeal swallowing - whether volitionally or experimentally initiated - are largely robust against disruption of primary cortical motor networks, supporting a key role of medullary CPGs in the motor control of sequential pharyngeal swallowing.

Freezing of Swallowing.

Swallowing deficits and freezing phenomena represent severe parkinsonian features. Freezing as a symptom occurring during swallowing has not been reported on yet. We report on 3 patients with probable PSP-parkinsonism (PSP-P) who manifested freezing of swallowing (FOS). All 3 patients experienced severe weight loss in recent months. At examination, 1 patient had freezing of gait. Video fluoroscopy showed nonfunctional trembling movements of the tongue and palate during chewing and volitional swallowing, with a 6- to 8-Hz frequency that is typical for freezing episodes during walking and finger tapping. These freezing episodes were accompanied by impaired oral bolus transportation. The pharyngeal phase was not relevantly affected. FOS represents a novel disease feature of PSP-P. The feature may have fundamental, but potentially treatable, consequences for patients' health and quality of life and may be considered in patients with degenerative parkinsonism who experience severe and unexplained weight loss.

Impact of proprioception during the oral phase on initiating the swallowing reflex.

We hypothesized that proprioceptive signals during the oral phase play a pivotal role in the initiation of pharyngeal phase during volitional swallowing. Therefore, we tested if swallowing could be modified by changing the amount of proprioceptive feedback from a number of different receptors while holding a food bolus in the mouth and clenching. Basic research. Surface electromyography (sEMG) recordings of the masticatory muscles were obtained during volitional swallowing movements from seven healthy adults with no clinical history of swallowing difficulties. The swallowing procedure involved holding 5 ml of jelly on the tongue before swallowing it completely, according to visual cues on a computer display. Initiation of the swallowing reflex was detected by an anterior shift of the thyroid cartilage using a laser displacement sensor and by submental sEMG signals. To vary the proprioceptive input, the participants were instructed to occlude their teeth at various intensities (weak, intermediate, and strong) while holding the 5-ml jelly bolus on the tongue. Rectified and integrated sEMG (iEMG) signals obtained from the submental area showed two upward deflections. Contractile forces of the masseter muscles showed significant negative values for Pearson correlation coefficient against time intervals from the onset of the second submental iEMG deflection to the onset of the anterior shift of the thyroid cartilage in six of the seven participants (average -0.534, standard deviation 0.176). Contractile forces of the masseter muscles during occlusion tended to correlate negatively with electromechanical delays on suprahyoid muscle contraction. NA Laryngoscope, 126:1595-1599, 2016.

Central Nervous System Control of Voice and Swallowing.

This review of the central nervous control systems for voice and swallowing has suggested that the traditional concepts of a separation between cortical and limbic and brain stem control should be refined and be more integrative. For voice production, a separation of the nonhuman vocalization system from the human learned voice production system has been posited based primarily on studies of nonhuman primates. However, recent humans studies of emotionally based vocalizations and human volitional voice production have shown more integration between these two systems than previously proposed. Recent human studies have shown that reflexive vocalization as well as learned voice production not involving speech involve a common integrative system. However, recent studies of nonhuman primates have provided evidence that some cortical activity vocalization and cortical changes occur with training during vocal behavior. For swallowing, evidence from the macaque and functional brain imaging in humans indicates that the control for the pharyngeal phase of swallowing is not primarily under brain stem mechanisms as previously proposed. Studies suggest that the initiation and patterning of swallowing for the pharyngeal phase is also under active cortical control for both spontaneous as well as volitional swallowing in awake humans and nonhuman primates.

Quantitative analysis of BOLD-fMRIs of the central swallowing cortex in normal adults

Objective To investigate the distribution and characteristics of the central swallowing cortex in normal adults. Methods Blood-oxygen level dependent functional MRIs (BOLD-fMRIs) were recorded from 10 normal, right-handed volunteers during swallowing. The volume of the central cortex activated and the activation intensity were recorded. Results During the experiment there were significant differences in volume but not in intensity between the BA4, BA40, BA32 and BA13 areas activated on the two sides. No significant differences were observed in either the volume or the intensity of the activated BA6/8 and BA24 areas. Moreover, significantly more areas in the left hemisphere were activated when swallowing than in the right hemisphere, with the laterality index value being 15.22%. Conclusion Normal adults' volitional swallowing is triggered in the BA13 area of the insula and the BA24/32 area of the anterior cingulate cortex. It is planned in the BA40 area of the supramarginal gyrus and the BA6 and 8 areas and implemented in the primary motor cortex of the pharynx oralis. One hemisphere clearly dominates in the cortical control of volitional swallowing. Key words: Swallowing; Cortical centers; Laterality; Control; BOLD-fMRI

Measurement of cerebral blood volume dynamics during volitional swallowing using functional near-infrared spectroscopy: An exploratory study

The aim of this study was to examine cerebral blood volume dynamics during volitional swallowing using multi-channel functional near-infrared spectroscopy (fNIRS) to understand the basic cortical activation patterns. Fifteen volunteers (age, 26.5±1.3 years, mean±SD) performed volitional swallowing of a 5-ml bolus of water as a task. A 52-channel fNIRS system was used for measuring oxy–Hb levels. We determined the oxy–Hb concentration changes in each channel by calculating the differences between rest and task oxy–Hb levels. Differences in rest and task data were assessed using a paired-t test (p<0.05). A significant increase in oxy–Hb was found in 21 channels. The cortical regions that exhibited increased oxy–Hb concentration included the bilateral precentral gyrus, postcentral gyrus, inferior frontal gyrus, superior temporal gyrus, middle temporal gyrus, and supramarginal gyrus. These data provide the first description of cortical activation patterns during volitional swallowing using fNIRS, which will be useful for the evaluation of dysphasia and the effects of the rehabilitation.

Pharyngeal pressure differences between four types of swallowing in healthy participants

PurposeThe aim of this observational study was to identify biomechanical differences, as measured by pharyngeal manometric pressure patterns, between discrete and continuous water swallowing, as well as volitionally initiated and reflexive swallowing. MethodsUsing pharyngeal manometry, swallowing-related pressures from 24 young healthy individuals were recorded at three locations: upper pharynx, mid-pharynx and upper oesophageal sphincter (UES) during four swallowing conditions: discrete saliva swallowing, discrete 10ml water swallowing, volitional continuous water swallowing, and reflexive continuous water swallowing. Measures of peak pressure and pressure duration at each level were compared across conditions using repeated-measures analysis of variance. ResultsUES nadir pressure during saliva swallowing was lower than during water swallowing conditions (p<0.05). In addition, nadir pressure during discrete 10ml water swallowing was lower than during reflexive and volitional continuous water swallowing conditions (p<0.05). Saliva swallowing produced longer pressure duration than water swallowing conditions at the upper pharynx (p<0.05). Saliva swallowing produced pressure of greater duration than reflexive continuous water swallowing at mid-pharynx (p<0.05). Further, discrete 10ml water swallowing produced longer UES opening duration and longer pharyngeal pressure generation (p<0.05) than reflexive continuous water swallowing or saliva swallowing. ConclusionPressure generation differs between swallowing types and bolus types at the level of the UES in particular. These physiological differences between swallowing and bolus types may support clinical decisions for individuals with impaired swallowing.

Pharyngeal electrical stimulation can modulate swallowing in cortical processing and behavior — Magnetoencephalographic evidence

BackgroundThe act of swallowing is a complex neuromuscular function that is processed in a distributed network involving cortical, subcortical and brainstem structures. Difficulty in swallowing arises from a variety of neurologic diseases for which therapeutic options are currently limited. Pharyngeal electrical stimulation (PES) is a novel intervention designed to promote plastic changes in the pharyngeal motor cortex to aid dysphagia rehabilitation. In the present study we evaluate the effect of PES on cortical swallowing network activity and associated changes in swallowing performance. MethodsIn a randomized, crossover study design 10min of real (0.2-ms pulses, 5Hz, 280V, stimulation intensity at 75% of maximum tolerated threshold) or sham PES were delivered to 14 healthy volunteers in two separate sessions. Stimulation was delivered via a pair of bipolar ring electrodes mounted on an intraluminal catheter positioned in the pharynx. Before and after each intervention swallowing capacity (ml/s) was tested using a 150ml-water swallowing stress test. Event-related desynchronization (ERD) of cortical oscillatory activity during volitional swallowing was recorded applying whole-head magnetoencephalography before, immediately after and 45min past the intervention. ResultsA prominent reduction of ERD in sensorimotor brain areas occurred in the alpha and beta frequency ranges immediately after real PES but not after sham stimulation (p<0.05) and had faded after 45min. Volume per swallow and swallowing capacity significantly increased following real stimulation only. ConclusionAttenuation of ERD following PES reflects stimulation-induced increased swallowing processing efficiency, which is associated with subtle changes in swallowing function in healthy subjects. Our data contribute evidence that swallowing network organization and behavior can effectively be modulated by PES.