Brain Activation During Oral Exercises Used for Dysphagia Rehabilitation in Healthy Human Subjects: A Functional Magnetic Resonance Imaging Study

Cerebellar control of targeted tongue movements

The cerebellum is critical for coordinating movements related to eating, drinking and swallowing, all of which require proper control of the tongue. Cerebellar Purkinje cells can encode tongue movements, but it is unclear how their simple spikes and complex spikes induce changes in the shape of the tongue that contribute to goal-directed movements. To study these relations, we recorded and stimulated Purkinje cells in the vermis and hemispheres of mice during spontaneous licking from a stationary or moving water spout. We found that Purkinje cells can encode rhythmic licking with both their simple spikes and complex spikes. Increased simple spike firing during tongue protrusion induces ipsiversive bending of the tongue. Unexpected changes in the target location trigger complex spikes that alter simple spike firing during subsequent licks, adjusting the tongue trajectory. Furthermore, we observed increased complex spike firing during behavioural state changes at both the start and the end of licking bouts. Using machine learning, we confirmed that alterations in Purkinje cell activity accompany licking, with different Purkinje cells often exerting heterogeneous encoding schemes. Our data highlight that directional movement control is paramount in cerebellar function and that modulation of the complex spikes and that of the simple spikes are complementary during acquisition and execution of sensorimotor coordination. These results bring us closer to understanding the clinical implications of cerebellar disorders during eating, drinking and swallowing. KEY POINTS: When drinking, mice make rhythmic tongue movements directed towards the water source. Cerebellar Purkinje cells can fire rhythmically in tune with the tongue movements. Purkinje cells encode changes in the position of the water source with complex spikes. Purkinje cell simple spike firing affects the direction of tongue movements. Purkinje cells that report changes in the position of the target can also adjust movements in the right direction.

Cortical Activation during Swallowing Exercise Tasks: an fNIRS Pilot Study

This pilot study used functional near-infrared spectroscopy (fNIRS) to examine brain activity in selected regions of the left motor and sensory cortex while doing swallowing-related tasks. Specifically, differences in cortical activation during normal saliva swallows, effortful swallows, and tongue pressing were investigated. Nine healthy, right-handed adults (5 female, 4 male; Age: 22-30 years) were recruited. The tasks included were (1) normal saliva swallowing, (2) effortful saliva swallowing, and (3) lingual pressing against the palate. Each task was completed three times in a block, for a total of five blocks. Blocks were randomized and presented with set time intervals using PsychoPy. Motor activity was highest during effortful swallows, followed by normal swallows, and lingual presses. Activation in the sensory region was not significantly different across tasks; however, effortful swallows elicited the highest mean peak activation. Our findings suggest that fNIRS can be a viable imaging method used to examine differences in cortical activity in the context of swallowing. Its applicability in future dysphagia research should be explored.

Anterior Cervical Spine Surgery Complicated With Dysphagia

Anterior cervical spine surgery is a common type of neck surgery in orthopaedics. Swallowing disorder is one of the most common complications after surgery. It is characterized by food entering the esophagus from the mouth through the pharynx. The process of reaching the stomach is hampered and leads to increases in a range of risk factors that affect the health of the patient. This article reviews relevant literature reports from recent years retrieved from various national and international medical databases, aiming to find more economical, effective, and simple perioperative nursing strategies for patients with cervical anterior surgery through evidence-based thinking and methods, with the aim of developing a personalized care model that is easy to implement and has a long-lasting effect and a wide range of rehabilitation benefits to better serve patients.

Videofluoroscopic Swallowing Study Features and Resting-State Functional MRI Brain Activity for Assessing Swallowing Differences in Patients with Mild Cognitive Impairment and Risk of Dysphagia

To examine the swallowing characteristics in patients with mild cognitive impairment (MCI) and dysphagia risk and explore brain activity changes using regional homogeneity (ReHo) with resting-state functional magnetic resonance imaging (rs-fMRI). We included 28 patients with MCI and dysphagia risk and 17 age-matched older adults. All participants underwent neurological, cognitive examinations, and a videofluoroscopic swallowing study (VFSS). We quantitatively analyzed the VFSS temporal and kinetic parameters of the 5- and 10-mL swallows. The participants underwent rs-fMRI, and the ReHo values were calculated. Differences in the swallowing physiology and rs-fMRI findings between participants with MCI and controls were analyzed. Correlation analyses were also conducted. Compared to the control group, patients with MCI and dysphagia risk had lower global cognition scores, longer 10-mL oral transit times (OTTs), and lower executive function scores. ReHo in the bilateral inferior occipital lobes (IOLs) and left prefrontal lobe decreased in patients with MCI and dysphagia risk compared to participants in the control group. In patients with MCI, the 10-mL OTT was negatively correlated with the Montreal Cognitive Assessment (MoCA) score, and the ReHo values were positive correlated with quantitative temporal swallowing measurements using canonical correlation analysis. Mediation analysis revealed that the ReHo values of the left and right IOL acted as significant mediators between the MoCA score and the 10-mL OTT. We found that individuals with MCI and dysphagia risk, verified by reduced MoCA scores, demonstrated prolonged OTTs when swallowing larger boluses compared with age-matched controls. There was a negative correlation between the MoCA score and 10-mL OTT, which was partially mediated by the left and right IOL ReHo values, suggesting that functional changes in the IOLs and left prefrontal lobe associated with oral swallowing status and cognitive level in individuals with MCI and dysphagia risk.

Effect of Tongue-Pressure Resistance Training in Poststroke Dysphagia Patients With Oral Motor Dysfunction: A Randomized Controlled Trial

OBJECTIVES

The aims of the study were to investigate the effect of tongue-pressure resistance training in poststroke dysphagia patients with oral motor dysfunction and to examine the therapeutic value of tongue-pressure resistance training in the oral and pharyngeal phases.

DESIGN

Patients were divided into an experimental and a control group. Both groups received 30 mins of traditional swallowing rehabilitation treatment every day for 4 wks. In addition, the experimental group received tongue-pressure resistance training for an extra 20 mins/d. Maximum tongue pressure and fiberoptic endoscopic examination of swallowing were assessed before and after treatments.

RESULTS

Compared with the control group, the experimental group showed significant improvement in Functional Communication Measure for swallowing, Oral Motor Function Scale, maximum tongue pressure, Murray Secretion Scale, Rosenbek Penetration-Aspiration Scale, and food residue in pyriform sinuses ( P < 0.05). There was no significant difference in food residue in epiglottic vallecula between both groups ( P > 0.05).

CONCLUSIONS

This study demonstrated that tongue-pressure resistance training is an effective approach to improve the overall swallowing function in patients with oral motor dysfunction. The improvement of oral motor function could facilitate the recovery of pharyngeal motor function. Tongue-pressure resistance training seems to have more clearance of residue in piriform sinus than epiglottic vallecula.

Neural Correlates of Oral Stereognosis—An fMRI Study

Oral stereognosis is the ability to recognize, discriminate and localize a bolus in the oral cavity. Clinical observation indicates deficits in oral stereognosis in patients with vascular or neurodegenerative diseases particularly affecting the parietal lobes. However, the precise neural representation of oral stereognosis remains unclear whereas the neural network of manual stereognosis has already been identified. We hypothesize that oral and manual stereognosis share common neuronal substrates whilst also showing somatotopic distribution. Functional magnetic resonance images (fMRI; Siemens Prisma 3 T) from 20 healthy right-handed participants (11 female; mean age 25.7 years) using a cross-modal task of oral and manual spatial object manipulation were acquired. Data were analyzed using FSL software using a block design and standard analytical and statistical procedures. A conjunction analysis targeted the common neuronal substrate for stereognosis. Activations associated with manual and oral stereognosis were found in partially overlapping fronto-parietal networks in a somatotopic fashion, where oral stereognosis is located caudally from manual stereognosis. A significant overlap was seen in the left anterior intraparietal sulcus. Additionally, cerebellar activations were shown particularly for the oral condition. Spatial arrangement of shaped boli in the oral cavity is associated with neuronal activity in fronto-parietal networks and the cerebellum. These findings have significant implications for clinical diagnostics and management of patients with lesions or atrophy in parietal lobule (e.g. Alzheimer’s disease, stroke). More studies are required to investigate the clinical effect of damage to these areas, such as loss of oral stereognosis or an impaired oral phase.

Beyond language: The unspoken sensory-motor representation of the tongue in non-primates, non-human and human primates

The English idiom "on the tip of my tongue" commonly acknowledges that something is known, but it cannot be immediately brought to mind. This phrase accurately describes sensorimotor functions of the tongue, which are fundamental for many tongue-related behaviors (e.g., speech), but often neglected by scientific research. Here, we review a wide range of studies conducted on non-primates, non-human and human primates with the aim of providing a comprehensive description of the cortical representation of the tongue's somatosensory inputs and motor outputs across different phylogenetic domains. First, we summarize how the properties of passive non-noxious mechanical stimuli are encoded in the putative somatosensory tongue area, which has a conserved location in the ventral portion of the somatosensory cortex across mammals. Second, we review how complex self-generated actions involving the tongue are represented in more anterior regions of the putative somato-motor tongue area. Finally, we describe multisensory response properties of the primate and non-primate tongue area by also defining how the cytoarchitecture of this area is affected by experience and deafferentation.

Effects of Tongue Pressure on Cerebral Blood Volume Dynamics: A Functional Near-Infrared Spectroscopy Study

Tongue pressure measurement (TPM) is an indicator of oral function. However, the association between tongue pressure and cerebral activation remains unclear. We used near-infrared spectroscopy (NIRS) to examine the correlation between cerebral cortex activation and tongue pressure stimulation against the anterior palatal mucosa. We measured voluntary maximum tongue pressure (MTP) using a TPM device; a pressure value of approximately 60% of the MTP was used for the experimental tongue pressure (MTP_60%). We examined the effect of oral functional tongue pressure stimulation against the anterior palatal mucosa on cerebral activation using NIRS in 13 adults. Tongue pressure stimulation caused significant changes in cerebral blood flow in some areas compared with controls (p < 0.05). We performed a correlation analysis (p < 0.05) between MTP_60% and changes in oxygenated hemoglobin in all 47 NIRS channels. MTP_60% triggered activation of the right somatosensory motor area and right dorsolateral prefrontal cortex and deactivation of the anterior prefrontal cortex (APFC). TPM balloon-probe insertion in the oral cavity activated the bilateral somatosensory motor area and deactivated the wide area of the APFC. Moreover, MTP_60% via the TPM balloon probe activated the bilateral somatosensory and motor cortex areas. Tongue pressure stimulation changes cerebral blood flow, and NIRS is useful in investigating the relationship between oral stimulation and brain function.

A systematic review and meta-analysis of the effects of intraoral treatments for neurogenic oropharyngeal dysphagia

BACKGROUND

Rehabilitative treatments for oropharyngeal dysphagia, including oromotor exercises and sensory stimulation, have been widely adopted into clinical practice. However, the effects of these treatments are mainly supported by exploratory studies. As such, their clinical efficacy remains uncertain.

OBJECTIVE

Our systematic review and meta-analysis aimed to evaluate the efficacy of intraoral treatments for neurogenic oropharyngeal dysphagia based on evidence from randomised controlled trials (RCTs).

METHODS

Six electronic databases were systematically searched between January 1970 and July 2021. Data were extracted and analysed by two independent reviewers. The outcome measure was changes in (any) relevant clinical swallowing-related characteristics.

RESULTS

Data from 285 dysphagic patients were collected from 8 RCT studies across a range of intraoral dysphagia treatments. The pooled effect size of all intraoral dysphagia treatments was non-significant compared to control comparators (SMD [95%CI] = 0.23 [-0.22, 0.69], p = .31; I²  = 73%). Subgroup analysis revealed that the pooled effect sizes were also non-significant for oromotor exercises (device-facilitated lip resistance exercises and tongue exercises) (SMD [95%CI] = 0.11 [-0.76, 0.97]; p = .81; I²  = 88%) and sensory stimulation (thermal-tactile, thermo-chemical and electrical stimulation) (SMD [95%CI] = 0.35 [-0.03, 0.72]; p = .07; I²  = 0%).

CONCLUSIONS

Our results showed that overall, intraoral dysphagia treatments, including oromotor exercises and sensory stimulation, do not show beneficial effects for neurogenic oropharyngeal dysphagia. The evidence for these treatments remains weak and currently inadequate to support clinical use. Large-scale, multi-centre RCTs are warranted to fully explore their clinical efficacy.

Adaptive brain activity changes during tongue movement with palatal coverage from fMRI data

Successful adaptation to wearing dentures with palatal coverage may be associated with cortical activity changes related to tongue motor control. The purpose was to investigate the brain activity changes during tongue movement in response to a new oral environment. Twenty-eight fully dentate subjects (mean age: 28.6-years-old) who had no experience with removable dentures wore experimental palatal plates for 7 days. We measured tongue motor dexterity, difficulty with tongue movement, and brain activity using functional magnetic resonance imaging during tongue movement at pre-insertion (Day 0), as well as immediately (Day 1), 3 days (Day 3), and 7 days (Day 7) post-insertion. Difficulty with tongue movement was significantly higher on Day 1 than on Days 0, 3, and 7. In the subtraction analysis of brain activity across each day, activations in the angular gyrus and right precuneus on Day 1 were significantly higher than on Day 7. Tongue motor impairment induced activation of the angular gyrus, which was associated with monitoring of the tongue's spatial information, as well as the activation of the precuneus, which was associated with constructing the tongue motor imagery. As the tongue regained the smoothness in its motor functions, the activation of the angular gyrus and precuneus decreased.

Gastrointestinal microecology: a crucial and potential target in acute pancreatitis

In the early stage of acute pancreatitis (AP), abundant cytokines induced by local pancreatic inflammation enter the bloodstream, further cause systemic inflammatory response syndrome (SIRS) by "trigger effect", which eventually leads to multiple organ dysfunction syndrome (MODS). During SIRS and MODS, the intestinal barrier function was seriously damaged accompanied by the occurrence of gut-derived infection which forms a "second hit summit" by inflammatory overabundance. Gastrointestinal microecology, namely the biologic barrier, could be transformed into a pathogenic state, which is called microflora dysbiosis when interfered by the inflammatory stress during AP. More and more evidences indicate that gastrointestinal microflora dysbiosis plays a key role in "the second hit" induced by AP gut-derived infection. Therefore, the maintenance of gastrointestinal microecology balance is likely to provide an effective method in modulating systemic infection of AP. This article reviewed the progress of gastrointestinal microecology in AP to provide a reference for deeply understanding the pathogenic mechanisms of AP and identifying new therapeutic targets.

Real-world Effectiveness of Speech Therapy Time on Cognitive Recovery in Older Patients with Acute Stroke

Objective

The purpose of this research was to investigate the real-world effectiveness of speech therapy time on cognitive recovery in older patients with acute stroke.

Methods

The participants of this retrospective cohort study were hospitalized patients with acute stroke registered in the Japan Rehabilitation Database between December 2005 and September 2014. The patients were divided into two groups according to the amount of time they spent undergoing speech therapy, i.e., a high-intensity speech therapy group and a control group. Multivariate linear regression analysis was performed to assess the association between cognitive Functional Independence Measure efficiency and high-intensity speech therapy.

Results

Of the 3341 eligible stroke patients (mean age: 77 years) extracted from the database, 53% received high-intensity speech therapy. Patients in the high-intensity speech therapy group had significantly higher cognitive Functional Independence Measure efficiency scores than those in the control group (mean, 0.17 vs. 0.10, respectively; P < 0.001). Multivariate regression analysis showed that cognitive Functional Independence Measure efficiency was significantly and positively correlated with high-intensity speech therapy (coefficient, 0.03; 95% confidence interval, 0.004-0.056; P = 0.026).

Conclusions

These data suggest that a large amount of speech therapy time in older patients with acute stroke is a significant predictor of good cognitive recovery. Increased amounts of speech therapy for such patients may lead to better cognitive recovery after stroke.

Nonspeech Oral Movements and Oral Motor Disorders: A Narrative Review

PURPOSE

Speech and other oral functions such as swallowing have been compared and contrasted with oral behaviors variously labeled quasispeech, paraspeech, speechlike, and nonspeech, all of which overlap to some degree in neural control, muscles deployed, and movements performed. Efforts to understand the relationships among these behaviors are hindered by the lack of explicit and widely accepted definitions. This review article offers definitions and taxonomies for nonspeech oral movements and for diverse speaking tasks, both overt and covert.

METHOD

Review of the literature included searches of Medline, Google Scholar, HighWire Press, and various online sources. Search terms pertained to speech, quasispeech, paraspeech, speechlike, and nonspeech oral movements. Searches also were carried out for associated terms in oral biology, craniofacial physiology, and motor control.

RESULTS AND CONCLUSIONS

Nonspeech movements have a broad spectrum of clinical applications, including developmental speech and language disorders, motor speech disorders, feeding and swallowing difficulties, obstructive sleep apnea syndrome, trismus, and tardive stereotypies. The role and benefit of nonspeech oral movements are controversial in many oral motor disorders. It is argued that the clinical value of these movements can be elucidated through careful definitions and task descriptions such as those proposed in this review article.

Neuronal correlates of voluntary facial movements

Whereas the somatotopy of finger movements has been extensively studied with neuroimaging, the neural foundations of facial movements remain elusive. Therefore, we systematically studied the neuronal correlates of voluntary facial movements using the Facial Action Coding System (FACS, Ekman et al., 2002). The facial movements performed in the MRI scanner were defined as Action Units (AUs) and were controlled by a certified FACS coder. The main goal of the study was to investigate the detailed somatotopy of the facial primary motor area (facial M1). Eighteen participants were asked to produce the following four facial movements in the fMRI scanner: AU1+2 (brow raiser), AU4 (brow lowerer), AU12 (lip corner puller) and AU24 (lip presser), each in alternation with a resting phase. Our facial movement task induced generally high activation in brain motor areas (e.g., M1, premotor cortex, supplementary motor area, putamen), as well as in the thalamus, insula, and visual cortex. BOLD activations revealed overlapping representations for the four facial movements. However, within the activated facial M1 areas, we could find distinct peak activities in the left and right hemisphere supporting a rough somatotopic upper to lower face organization within the right facial M1 area, and a somatotopic organization within the right M1 upper face part. In both hemispheres, the order was an inverse somatotopy within the lower face representations. In contrast to the right hemisphere, in the left hemisphere the representation of AU4 was more lateral and anterior compared to the rest of the facial movements. Our findings support the notion of a partial somatotopic order within the M1 face area confirming the “like attracts like” principle (Donoghue et al., 1992). AUs which are often used together or are similar are located close to each other in the motor cortex.

Role of cerebellum in deglutition and deglutition disorders

The objective of this review is to gather available evidence regarding the role of the cerebellum in swallowing-related functions. We reviewed literature on cerebellar functions related to healthy swallowing, patterns of dysphagia in individuals with cerebellar lesions, and the role of the cerebellum in therapeutic intervention of neurogenic dysphagia since 1980. A collective understanding of these studies suggests that both hemispheres of the cerebellum, predominantly the left, participate in healthy swallowing. Also, it appears that the cerebellum contributes to specific physiological functions within the entire act of swallowing, but this is not clearly understood. The understanding of patterns of dysphagia in cerebellar lesions remains ambiguous with equivocal results across a small number of studies. The cerebellum appears to be involved in oral exercises for dysphagia in the relationship between oral movements in such exercises, and deglutition remains uncertain. There is increasing evidence to suggest successful use of transcranial magnetic stimulation of the cerebellum to improve neuromotor control of swallowing. Future studies should address activation of the cerebellum with swallowing of different consistencies and tastes in healthy adults to gain better insights. Studies should also investigate dynamics of neural activation during different stages of recovery from dysphagia following strokes to cortical centers to determine if the cerebellum plays a compensatory role during instances of increased neural demands.

Compensatory recombination phenomena of neurological functions in central dysphagia patients

We speculate that cortical reactions evoked by swallowing activity may be abnormal in patients with central infarction with dysphagia. The present study aimed to detect functional imaging features of cerebral cortex in central dysphagia patients by using blood oxygen level-dependent functional magnetic resonance imaging techniques. The results showed that when normal controls swallowed, primary motor cortex (BA4), insula (BA13), premotor cortex (BA6/8), supramarginal gyrus (BA40), and anterior cingulate cortex (BA24/32) were activated, and that the size of the activated areas were larger in the left hemisphere compared with the right. In recurrent cerebral infarction patients with central dysphagia, BA4, BA13, BA40 and BA6/8 areas were activated, while the degree of activation in BA24/32 was decreased. Additionally, more areas were activated, including posterior cingulate cortex (BA23/31), visual association cortex (BA18/19), primary auditory cortex (BA41) and parahippocampal cortex (BA36). Somatosensory association cortex (BA7) and left cerebellum in patients with recurrent cerebral infarction with central dysphagia were also activated. Experimental findings suggest that the cerebral cortex has obvious hemisphere lateralization in response to swallowing, and patients with recurrent cerebral infarction with central dysphagia show compensatory recombination phenomena of neurological functions. In rehabilitative treatment, using the favorite food of patients can stimulate swallowing through visual, auditory, and other nerve conduction pathways, thus promoting compensatory recombination of the central cortex functions.