Decoding human swallowing via electroencephalography: a state-of-the-art review

Short-term cortical activation changes associated with postural compensation in swallowing

Compensatory strategies used to treat dysphagia, like the chin-down and chin-up positions, are often employed by speech-language pathologists to enhance swallowing safety. However, their effects on cortical neural responses remain unclear. This study aimed to investigate the cortical hemodynamic responses to swallowing across three head positions -chin-down, chin-neutral, and chin-up - using functional near-infrared spectroscopy (fNIRS) in the bilateral precentral and postcentral gyrus regions of interest. Twenty-six healthy adults completed 32 swallows of 5 ml water in each head position. Results revealed short-term cortical activation increases for chin-up swallows compared to both chin-neutral (mean difference = 1.2, SE = 0.18, p = .048) and chin-down swallows (mean difference = 0.76, SE = 0.18, p = .009). These findings suggest that postural changes during swallowing induce immediate neural adaptations in people without swallowing difficulty. These modifications likely reflect the necessary sensory and neuromuscular adaptations required for safe swallowing in different head positions, with less hyolaryngeal movement needed for a chin-down swallow and more movement needed for a chin-up swallow. While challenging swallow conditions, like the chin-up, may offer promising therapeutic potential, caution is warranted considering the associated safety risk, and further investigation is needed. This study provides insights into the immediate effects of head positions on cortical activity during swallowing and highlights avenues for future research in dysphagia rehabilitation.

Unraveling the difference in flavor characteristics of Huangjiu fermented with different rice varieties using dynamic sensory evaluation and comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry

To investigate the specific differences in flavor characteristics of Huangjiu fermented with different rice varieties, dynamic sensory evaluation, comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS) and multivariate statistical analysis were employed. Dynamic sensory evaluation methods including temporal dominance of sensations (TDS) and temporal check all that apply (TCATA) were applied to explore the differences and variations in sensory attributes. The sensory results showed that the intensity of astringency and post-bitterness in the Huangjiu fermented with glutinous rice was weaker while ester and alcoholic aroma were more prominent than the one fermented with japonica rice. The results of free amino acids and aroma compounds analysis indicated that the amino acids were mainly sweet and bitter amino acids, and some key aroma compounds were predominant in the Huangjiu fermented with glutinous rice, such as ethyl butyrate (OAV: 38-59), 3-methylthiopropionaldehyde (OAV: 47-96), ethyl caprylate (OAV: 30-38), while nonanal, phenyl acetaldehyde and vanillin contributed significantly to the Huangjiu fermented with japonica rice. The multivariate statistical analysis further confirmed that 17 compounds (VIP > 1 and p < 0.05) could be supposed to be the key compouns that cause significant flavor differences in Huangjiu samples fermented with different brewing rice. Moreover, partial least-squares analysis revealed that most compounds (ethyl butyrate, 3-penten-2-one, isoamyl acetate, and so on) correlated with ester and alcoholic aroma. The results could provide basic data and theoretical basis for the selection of raw materials in Huangjiu.

Electrokinesiographic Study of Oropharyngeal Swallowing in Neurogenic Dysphagia

Electrokinesiographic study of swallowing (EKSS) can be useful for the assessment of patients with suspected or overt neurogenic dysphagia. EKSS consists of multichannel recording of the electromyographic (EMG) activity of the suprahyoid/submental muscle complex (SHEMG), the EMG activity of the cricopharyngeal muscle (CPEMG), and the laryngopharyngeal mechanogram (LPM). The LPM is an expression of the mechanical changes that the laryngopharyngeal structures undergo during the pharyngeal phase of swallowing. This method allows detailed evaluation of the magnitude, duration and temporal relations of the different events that characterize oropharyngeal swallowing, and thus in-depth exploration both of physiological deglutition mechanisms and of pathophysiological features of swallowing in neurogenic dysphagia. Furthermore, EKSS can guide dysphagia treatment strategies, allowing identification of optimal solutions for single patients. For instance, CPEMG recording can identify incomplete or absent relaxation of the upper esophageal sphincter during the pharyngeal phase of swallowing, thus suggesting a therapeutic approach based on botulinum toxin injection into the cricopharyngeal muscle. More recently, the 'shape' of SHEMG and the reproducibility of both SHEMG and LPM over repeated swallowing acts have been implemented as novel electrokinesiographic parameters. These measures could be valuable for straightforward non-invasive investigation of dysphagia severity and response to dysphagia treatment in clinical practice.

Effect of Capsaicin Atomization on Cough and Swallowing Function in Patients With Hemorrhagic Stroke: A Randomized Controlled Trial

BACKGROUND

Patients with hemorrhagic stroke have high mortality and disability rates. Nevertheless, early rehabilitation interventions can improve their outcomes. We aimed to apply capsaicin atomization as early intervention to patients with hemorrhagic stroke and explore improvements in cough and swallowing functions.

METHOD

Patients with hemorrhagic stroke were randomly divided into the control group, which received routine care, and the intervention group, which underwent the capsaicin solution nebulization scheme in addition to routine care. Differences in the presence/absence of cough reflex and number of coughs in response to capsaicin, the presence/absence of swallowing reflex in response to water, the presence/absence of postswallow residue, substance P (SP) concentration, and pulmonary inflammation between the two groups were determined before and after the intervention.

RESULTS

A total of 53 patients with hemorrhagic stroke were included. Results showed no statistically significant difference in cough reflex in both groups after the intervention (p > .05). The degree of cough in the intervention group was stronger than that in the control group (p = .046). No statistically significant difference was observed in the number of patients with swallowing reflex in response to water between the groups (p > .05). The presence/absence of postswallow residue of the intervention group was stronger than that of the control group (p = .032). No statistically significant difference was observed between the Glasgow Coma Scale scores of the groups after the intervention (p > .05). SP in the intervention group was significantly increased (p = .031). The Clinical Pulmonary Infection Score was significantly lower in the control group, and the difference was statistically significant (p = .028).

CONCLUSIONS

Capsaicin nebulization can help enhance the number of coughs in response to capsaicin, reduce postswallow residue, and increase the level of SP in patients with hemorrhagic stroke and has a positive effect on pulmonary inflammation. This study provides intervention points for cough and swallowing rehabilitation after a hemorrhagic stroke.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21956903.

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.

Electrophysiological Measures of Swallowing Functions: A Systematic Review

The purpose of this systematic review was to examine the application of event-related potentials (ERPs) to investigate neural processes of swallowing functions in adults with and without dysphagia. Computerized literature searches were performed from three search engines. Studies were screened using Covidence (Cochrane tool) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards (PRISMA-2009). A total of 759 studies were initially retrieved, of which 12 studies met inclusion criteria. Electrophysiological measures assessing swallowing functions were identified in two major ERP categories: (1) sensory potentials and (2) pre-motor potentials. Approximately 80% of eligible studies demonstrated strong methodological quality, although most employed a case series or case-control study design. Pharyngeal sensory-evoked potentials (PSEPs) were used to assess pharyngeal afferent cortical processing. The temporal sequence of the PSEP waveforms varied based on the sensory stimuli. PSEPs were delayed with localized scalp maps in patients with dysphagia as compared to healthy controls. The pre-motor ERPs assessed the cortical substrates involved in motor planning for swallowing, with the following major neural substrates identified: pre-motor cortex, supplementary motor area, and primary sensorimotor cortex. The pre-motor ERPs differed in amplitude for the swallow task (saliva versus liquid swallow), and the neural networks differed for cued versus non-cued task of swallowing suggesting differences in cognitive processes. This systematic review describes the application of electrophysiological measures to assess swallowing function and the promising application for furthering understanding of the neural substrates of swallowing. Standardization of protocols for use of electrophysiological measures to examine swallowing would allow for aggregation of study data to inform clinical practice for dysphagia rehabilitation.

Can Swallowing Cerebral Neurophysiology Be Evaluated during Ecological Food Intake Conditions? A Systematic Literature Review

Swallowing is a complex function that relies on both brainstem and cerebral control. Cerebral neurofunctional evaluations are mostly based on functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), performed with the individual laying down; which is a non-ecological/non-natural position for swallowing. According to the PRISMA guidelines, a review of the non-invasive non-radiating neurofunctional tools, other than fMRI and PET, was conducted to explore the cerebral activity in swallowing during natural food intake, in accordance with the PRISMA guidelines. Using Embase and PubMed, we included human studies focusing on neurofunctional imaging during an ecologic swallowing task. From 5948 unique records, we retained 43 original articles, reporting on three different techniques: electroencephalography (EEG), magnetoencephalography (MEG) and functional near infra-red spectroscopy (fNIRS). During swallowing, all three techniques showed activity of the pericentral cortex. Variations were associated with the modality of the swallowing process (volitional or non-volitional) and the substance used (mostly water and saliva). All techniques have been used in both healthy and pathological conditions to explore the precise time course, localization or network structure of the swallowing cerebral activity, sometimes even more precisely than fMRI. EEG and MEG are the most advanced and mastered techniques but fNIRS is the most ready-to-use and the most therapeutically promising. Ongoing development of these techniques will support and improve our future understanding of the cerebral control of swallowing.

A deep learning algorithm based on 1D CNN-LSTM for automatic sleep staging

BACKGROUND

Sleep staging is an important part of sleep research. Traditional automatic sleep staging based on machine learning requires extensive feature extraction and selection.

OBJECTIVE

This paper proposed a deep learning algorithm without feature extraction based on one-dimensional convolutional neural network and long short-term memory.

METHODS

The algorithm can automatically divide sleep into 5 phases including awake period, non-rapid eye movement sleep period (N1 ∼ N3) and rapid eye movement using the electroencephalogram signals. The raw signal was processed by the wavelet transform. Then, the processed signal was directly input into the deep learning algorithm to obtain the staging result.

RESULTS

The accuracy of staging is 93.47% using the Fpz-Cz electroencephalogram signal. When using the Fpz-Cz and electroencephalogram signal, the algorithm can obtain the highest accuracy of 94.15%.

CONCLUSION

These results show that this algorithm is suitable for different physiological signals and can realize end-to-end automatic sleep staging without any manual feature extraction.

A Swallowing Decoder Based on Deep Transfer Learning: AlexNet Classification of the Intracranial Electrocorticogram

To realize a brain-machine interface to assist swallowing, neural signal decoding is indispensable. Eight participants with temporal-lobe intracranial electrode implants for epilepsy were asked to swallow during electrocorticogram (ECoG) recording. Raw ECoG signals or certain frequency bands of the ECoG power were converted into images whose vertical axis was electrode number and whose horizontal axis was time in milliseconds, which were used as training data. These data were classified with four labels (Rest, Mouth open, Water injection, and Swallowing). Deep transfer learning was carried out using AlexNet, and power in the high-[Formula: see text] band (75-150[Formula: see text]Hz) was the training set. Accuracy reached 74.01%, sensitivity reached 82.51%, and specificity reached 95.38%. However, using the raw ECoG signals, the accuracy obtained was 76.95%, comparable to that of the high-[Formula: see text] power. We demonstrated that a version of AlexNet pre-trained with visually meaningful images can be used for transfer learning of visually meaningless images made up of ECoG signals. Moreover, we could achieve high decoding accuracy using the raw ECoG signals, allowing us to dispense with the conventional extraction of high-[Formula: see text] power. Thus, the images derived from the raw ECoG signals were equivalent to those derived from the high-[Formula: see text] band for transfer deep learning.

A Randomized Controlled Trial Comparing Physical and Mental Lingual Exercise for Healthy Older Adults

Mental practice using motor imagery (MP-MI) has been shown to improve motor outcomes of upper and lower extremities especially when combined with physical exercise. Here, we studied community-dwelling, healthy older adults to determine the effects of including an MP-MI component with lingual strengthening exercise. In this pilot study, twenty-nine typically aging participants were assigned to an intervention group: physical lingual exercise (n = 7), physical and MP-MI lingual exercise (n = 8), MPMI lingual exercise (n = 7), or a control group (placebo exercise) (n = 7). All participants completed the assigned exercise regimen with three sessions per day, three days a week, for 6 consecutive weeks. Maximum isometric pressure (MIP) and regular effort saliva swallowing (RESS) pressure were collected at baseline and weeks 2, 4, and 6. A post hoc Bonferroni corrected treatment effect from baseline to week 6 was shown for only participants in the MP-MI/Physical exercise group for MIP (p = 0.003 MPMI/ Physical group; p = 0.11 Control group; p = 0.32 Physical only group; p = 0.14 MP-MI only group) and RESS (p = 0.009 MP-MI/Physical group; p = 0.14 Control group; p = 0.10 Physical only group; p = 0.04 MP-MI only group). Findings also indicate spontaneous carryover of significantly increased swallowing pressure when mental and physical exercise are combined. In conclusion, the potential effect of including an MPMI lingual exercise component in preventative and rehabilitative frameworks with older persons to possibly enhance functional swallowing improvement is promising and should be investigated.

Mental Practice Using Motor Imagery in Dysphagia Rehabilitation: A Survey of Practicing Speech-Language Pathologists

Mental practice (MP) using motor imagery is recognized as an effective clinical tool in rehabilitative medicine for improving motor performance. Preliminary data using MP in dysphagia rehabilitation are promising, though nothing is known about the current landscape among speech-language pathologists (SLPs) relating to MP implementation. This nationwide study surveys practicing SLPs about knowledge and practice patterns of using MP to gain a better understanding of the current knowledge, as well as perceived benefits and challenges in using MP. Descriptive data are reported and open-ended questions analyzed for emerging themes using inductive coding. Over half of the participants were familiar or somewhat familiar with motor imagery in the context of dysphagia rehabilitation, though only 16% of those SLPs reported using MP with a patient. Nearly 75% of respondents expressed interest in learning more about MP. Emerging themes include factors SLPs perceive to limit patient engagement, evidence-based practice concerns, and therapeutic environmental factors. More research on MP and access to training for clinicians is needed in the area of dysphagia rehabilitation to address acknowledged interest in MP.

Motor Imagery Practice and Increased Tongue Strength: A Case Series Feasibility Report

Purpose The aim of the study was to determine the effects of a 6-week progressive resistance tongue exercise protocol in mental practice form on tongue strength. Investigation begins in typically aging adults, a population susceptible to reduced tongue strength and dysphagia secondary to age-related changes in the swallowing mechanism. It was hypothesized that typically aging adults who perform a 6-week progressive resistance tongue exercise protocol in mental practice form would increase tongue strength. Method A prospective, case series intervention study was used. Six healthy women aged 53-78 years completed a 6-week mental practice tongue resistance exercise program utilizing motor imagery to imagine completion of tongue exercises. The main outcome was mean isometric maximum tongue pressures (tongue strength), which were collected at baseline and Weeks 2, 4, and 6 using the Iowa Oral Performance Instrument ( IOPI Medical, 2013 ). Results By Week 6 of the study, all participants had significantly increased their tongue strength compared to baseline. Conclusions The findings indicate that mental practice using motor imagery for tongue exercise may improve tongue strength in healthy individuals at risk for dysphagia and may thus represent a promising direction warranting further investigation in typically aging individuals and patients with dysphagia and decreased tongue strength.

Effect of individual food preferences on oscillatory brain activity

OBJECTIVES

During the anticipatory stage of swallowing, sensory stimuli related to food play an important role in the behavioral and neurophysiological aspects of swallowing. However, few studies have focused on the relationship between food preferences and oscillatory brain activity during the anticipatory stage of swallowing. Therefore, to clarify the effect of individual food preferences on oscillatory brain activity, we investigated the relationship between food preferences and oscillatory brain activity during the observation of food images.

METHODS

Here we examined this relationship using visual food stimuli and electroencephalography (EEG). Nineteen healthy participants were presented 150 images of food in a random order and asked to rate their subjective preference for that food on a 4-point scale ranging from 1 (don't want to eat) to 4 (want to eat). Oscillation analysis was performed using a Hilbert transformation for bandpass-filtered EEG signals.

RESULTS

The results showed that the oscillatory beta band power on C3 significantly decreased in response to favorite foods compared to disliked food.

CONCLUSION

This result suggests that food preferences may impact oscillatory brain activity related to swallowing during the anticipatory stage of swallowing. This finding may lead to the development of new swallowing rehabilitation techniques for patients with dysphagia by applying food preferences to modulate oscillatory brain activity.

The Prevalence of Dysphonia and Dysphagia in Patients with Vitamin D Deficiency

OBJECTIVE

To investigate the prevalence of phonatory and swallowing symptoms in patients with hypovitaminosis D.

METHODS/DESIGN

All patients presenting to the endocrinology clinic and investigated for vitamin D deficiency between January 2018 and April 2018 were asked to participate in this study. Demographic data included age, gender, allergy, and history of smoking. Patients filled Voice handicap Index (VHI-10) and Eating Assessment Tool (EAT-10).

RESULTS

A total of 136 consecutive subjects presenting to the endocrinology clinic for vitamin D testing were included: 60 with hypovitaminosis D and 76 with no hypovitaminosis D. The mean vitamin D level in the study group and controls was 13.25 ng/mL and 31.91 ng/mL, respectively. There was no significant difference in the mean score of VHI-10, nor in the mean score of EAT-10 in patients with hypovitaminosis D versus those with no hypovitaminosis D (P value >0.05).

CONCLUSION

There was no significant difference in the prevalence of phonatory and dysphagia symptoms using VHI-10 and EAT-10 questionnaires between subjects with hypovitaminosis D and those with normal serum vitamin D levels.

Piezoelectric Polyacrylonitrile Nanofiber Film-Based Dual-Function Self-Powered Flexible Sensor

To meet the growing demands in flexible and wearable electronics, various sensors have been designed for detecting and monitoring the physical quantity changes. However, most of these sensors can only detect one certain kind of physical quantity based on a single mechanism. In this paper, we have fabricated a multifunctional sensor made from carbonized electrospun polyacrylonitrile/barium titanate (PAN-C/BTO) nanofiber film. It can detect two physical quantities (pressure and curvature), independently and simultaneously, by integrating piezoresistive, piezoelectric, and triboelectric effects. For flex sensing with the impedance change of PAN-C/BTO nanofiber films during bending, it had a sensitivity of 1.12 deg^-1 from 58.9° to 120.2° and a working range of 28°-150°. For self-powered force sensing, it had a gauge factor of 1.44 V·N^-1 within the range of 0.15-25 N. The sensor had a long stability over 60 000 cycles at both sensing modes. The inclusion of barium titanate nanoparticles (BTO NPs) into the nanofiber film had an over 2.4 times enhancement of sensitivity for pressure sensing because of the synergy of piezoelectric and triboelectric effects. On the basis of multifunction and modularity, a series of potential applications of the sensor were demonstrated, including sensing human's swallowing, walking gaits, finger flexure, and finger-tapping. The self-powered flexible dual-mode sensor has great application potential in human-computer interactive and smart wearable sensing systems.

Influence of attention and bolus volume on brain organization during swallowing

It has been shown that swallowing involves certain attentional and cognitive resources which, when disrupted can influence swallowing function with in dysphagic patient. However, there are still open questions regarding the influence of attention and cognitive demands on brain activity during swallowing. In order to understand how brain regions responsible for attention influence brain activity during swallowing, we compared brain organization during no-distraction swallowing and swallowing with distraction. Fifteen healthy male adults participated in the data collection process. Participants performed ten 1 ml, ten 5 ml, and ten 10 ml water swallows under both no-distraction conditions and during distraction while EEG signals were recorded. After standard pre-processing of the EEG signals, brain networks were formed using the time-frequency based synchrony measure. The brain networks formed were then compared between the two sets of conditions. Results showed that there are differences in the Delta, Theta, Alpha, Beta, and Gamma frequency bands between no-distraction swallowing and swallowing with distraction. Differences in the Delta and Theta frequency bands can be attributed to changes in subliminal processes, while changes in the Alpha and Beta frequency bands are directly associated with the various levels of attention and cognitive demands during swallowing process, and changes in the Gamma frequency band are due to changes in motor activity. Furthermore, we showed that variations in bolus volume influenced the swallowing brain networks in the Delta, Theta, Alpha, Beta, and Gamma frequency bands. Changes in the Delta, Theta, and Alpha frequency bands are due to sensory perturbations evoked by the various bolus volumes. Changes in the Beta frequency band are due to reallocation of cognitive demands, while changes in the Gamma frequency band are due to changes in motor activity produced by variations in bolus volume. These findings could potentially lead to the development of better understanding of the nature of dysphagia and various rehabilitation strategies for patients with neurogenic dysphagia who have altered attention or impaired cognitive functions.

Deep Belief Networks for Electroencephalography: A Review of Recent Contributions and Future Outlooks

Deep learning, a relatively new branch of machine learning, has been investigated for use in a variety of biomedical applications. Deep learning algorithms have been used to analyze different physiological signals and gain a better understanding of human physiology for automated diagnosis of abnormal conditions. In this paper, we provide an overview of deep learning approaches with a focus on deep belief networks in electroencephalography applications. We investigate the state-of-the-art algorithms for deep belief networks and then cover the application of these algorithms and their performances in electroencephalographic applications. We covered various applications of electroencephalography in medicine, including emotion recognition, sleep stage classification, and seizure detection, in order to understand how deep learning algorithms could be modified to better suit the tasks desired. This review is intended to provide researchers with a broad overview of the currently existing deep belief network methodology for electroencephalography signals, as well as to highlight potential challenges for future research.

Differences in brain networks during consecutive swallows detected using an optimized vertex-frequency algorithm

Patients with dysphagia can have higher risks of aspiration after repetitive swallowing activity due to the "fatigue effect". However, it is still unknown how consecutive swallows affect brain activity. Therefore, we sought to investigate differences in swallowing brain networks formed during consecutive swallows using a signal processing on graph approach. Data were collected from 55 healthy people using electroencephalography (EEG) signals. Participants performed dry swallows (i.e., saliva swallows) and wet swallows (i.e., water, nectar-thick, and honey thick swallows). After standard pre-processing of the EEG time series, brain networks were formed using the time-frequency-based synchrony measure, while signals on graphs were formed as a line graph of the brain networks. For calculating the vertex frequency information from the signals on graphs, the proposed algorithm was based on the optimized window size for calculating the windowed graph Fourier transform and the graph S-transform. The proposed algorithms were tested using synthetic signals and showed improved energy concentration in comparison to the original algorithm. When applied to EEG swallowing data, the optimized windowed graph Fourier transform and the optimized graph S-transform showed that differences exist in brain activity between consecutive swallows. In addition, the results showed higher differences between consecutive swallows for thicker liquids.

Spatiotemporal characteristics of the pharyngeal event-related potential in healthy subjects and older patients with oropharyngeal dysfunction

BACKGROUND

Oropharyngeal dysphagia (OD) is a highly prevalent symptom in older people. Appropriate oropharyngeal sensory feedback is essential for safe and efficient swallowing. However, pharyngeal sensitivity decreases with advancing age and could play a fundamental role in the physiopathology of swallowing dysfunction associated with aging. We aimed to characterize pharyngeal sensitivity and cortical response to a pharyngeal electrical stimulus in healthy volunteers (HV) and older patients with and without OD.

METHODS

Eight young HV, eight older HV without OD, and 14 older patients with OD were studied by electroencephalography through 32 scalp electrodes. Pharyngeal event-related potentials (ERP) were assessed following electrical stimulation of the pharynx. Sensory and tolerance thresholds to the electrical stimulus and latency, amplitude, and scalp current density of each ERP component were analyzed and compared. An ERP source localization study was also performed using the sLORETA software.

KEY RESULTS

Older participants (with and without OD) presented an increased sensory threshold to pharyngeal electrical stimulation (10.2 ± 1.7 mA and 11.5 ± 1.9 mA respectively), compared with young HV (6.0 ± 1.2 mA). The cortical activation of older HV in response to pharyngeal electrical stimulus was reduced compared with young HV (N2 amplitude: 0.22 ± 0.79 vs -3.10 ± 0.59, P<.05). Older patients with OD also presented disturbances to the pharyngo-cortical connection together with disrupted pattern of cortical activation.

CONCLUSIONS AND INFERENCES

Older people present a decline in pharyngeal sensory function, more severe in older patients with OD. This sensory impairment might be a critical pathophysiological element and a potential target for treatment of swallowing dysfunction in older patients.

A fast algorithm for vertex-frequency representations of signals on graphs

The windowed Fourier transform (short time Fourier transform) and the S-transform are widely used signal processing tools for extracting frequency information from non-stationary signals. Previously, the windowed Fourier transform had been adopted for signals on graphs and has been shown to be very useful for extracting vertex-frequency information from graphs. However, high computational complexity makes these algorithms impractical. We sought to develop a fast windowed graph Fourier transform and a fast graph S-transform requiring significantly shorter computation time. The proposed schemes have been tested with synthetic test graph signals and real graph signals derived from electroencephalography recordings made during swallowing. The results showed that the proposed schemes provide significantly lower computation time in comparison with the standard windowed graph Fourier transform and the fast graph S-transform. Also, the results showed that noise has no effect on the results of the algorithm for the fast windowed graph Fourier transform or on the graph S-transform. Finally, we showed that graphs can be reconstructed from the vertex-frequency representations obtained with the proposed algorithms.

Functional connectivity patterns of normal human swallowing: difference among various viscosity swallows in normal and chin-tuck head positions

Consuming thicker fluids and swallowing in the chin-tuck position has been shown to be advantageous for some patients with neurogenic dysphagia who aspirate due to various causes. The anatomical changes caused by these therapeutic techniques are well known, but it is unclear whether these changes alter the cerebral processing of swallow-related sensorimotor activity. We sought to investigate the effect of increased fluid viscosity and chin-down posture during swallowing on brain networks. 55 healthy adults performed water, nectar-thick, and honey thick liquid swallows in the neutral and chin-tuck positions while EEG signals were recorded. After pre-processing of the EEG timeseries, the time-frequency based synchrony measure was used for forming the brain networks to investigate whether there were differences among the brain networks between the swallowing of different fluid viscosities and swallowing in different head positions. We also investigated whether swallowing under various conditions exhibit small-world properties. Results showed that fluid viscosity affects the brain network in the Delta, Theta, Alpha, Beta, and Gamma frequency bands and that swallowing in the chin-tuck head position affects brain networks in the Alpha, Beta, and Gamma frequency bands. In addition, we showed that swallowing in all tested conditions exhibited small-world properties. Therefore, fluid viscosity and head positions should be considered in future swallowing EEG investigations.

Neural and cortical analysis of swallowing and detection of motor imagery of swallow for dysphagia rehabilitation-A review

Swallowing is an essential function in our daily life; nevertheless, stroke or other neurodegenerative diseases can cause the malfunction of swallowing function, ie, dysphagia. The objectives of this review are to understand the neural and cortical basis of swallowing and tongue, and review the latest techniques on the detection of motor imagery of swallow (MI-SW) and motor imagery of tongue movements (MI-TM), so that a practical system can be developed for the rehabilitation of poststroke dysphagia patients. Specifically, we firstly describe the swallowing process and how the swallowing function is assessed clinically. Secondly, we review the techniques that performed the neural and cortical analysis of swallowing and tongue based on different modalities such as functional magnetic resonance imaging, positron emission tomography, near-infrared spectroscopy (NIRS), and magnetoencephalography. Thirdly, we review the techniques that performed detection and analysis of MI-SW and MI-TM for dysphagia stroke rehabilitation based on electroencephalography (EEG) and NIRS. Finally, discussions on the advantages and limitations of the studies are presented; an example system and future research directions for the rehabilitation of stroke dysphagia patients are suggested.