Timing of cortical activation during spontaneous swallowing

Abstract

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

Nocturnal swallowing augments arousal intensity and arousal tachycardia

“…This suggests that afferents encoding airway pressures and touch are highly salient stimuli and that maintaining airway patency involves higher order vigilance. The swallow motor act is under constant somatosensory cortical surveillance (29), with neuronal activity increasing immediately prior to an automatic saliva swallow, and two peaks of activation that relate to the pharyngeal (2 s) and esophageal (15 to 20 s) swallow phases (29). Experts suggest that cortical representation is an important modifier of the involuntary swallow motor act and note problems with swallowing Fig.…”

“…It is a complex motor act, requiring precisely coordinated sequential activation and inhibition of various respiratory and nonrespiratory muscles regulated by a brain stem neuronal network, the so-called swallow central pattern generator (CPG) (26)(27)(28). Swallowing occurs episodically, triggered by sensory inputs or cortical commands, and is coordinated with rhythmic breathing, mastication, and other motor behaviors by the brainstem CPGs (27), and by feedback to higher level centers for sensorimotor planning and control (29,30). Thus, during quiet wakefulness, involuntary or reflexive swallows produce patterns of cortical and subcortical activation via sensory and central feedback (29)(30)(31)(32)(33)(34).…”

“…Swallowing occurs episodically, triggered by sensory inputs or cortical commands, and is coordinated with rhythmic breathing, mastication, and other motor behaviors by the brainstem CPGs (27), and by feedback to higher level centers for sensorimotor planning and control (29,30). Thus, during quiet wakefulness, involuntary or reflexive swallows produce patterns of cortical and subcortical activation via sensory and central feedback (29)(30)(31)(32)(33)(34). Swallows also trigger autonomic…”

Spontaneous Swallowing Frequency in Post-Stroke Patients with and Without Oropharyngeal Dysphagia: An Observational Study

“…Normal swallowing requires the participation of a widely extended cerebral network with final output motor commands occurring after activation of brainstem circuits involving the nuclei of the central pattern generators [ 18 , 19 ]. The integrity of this complex top-to-bottom neural axis is necessary for the coordination of the oropharyngeal swallow response during volitional swallows and ideal for reflexive or spontaneous swallows in order to adapt the motor response to the passage of the oral content through the oropharynx [ 20 , 21 ]. Spontaneous swallowing is, therefore, a protective aerodigestive oligosynaptic brainstem reflex, the primary trigger of which depends on a “peripheral” stimulus (saliva) but could also involve a central source and modulation mechanism [ 21 ] although this aspect is still under discussion.…”

Funcionalidade global, da deglutição e da comunicação de idosos com comprometimento cognitivo avançado

“…A deglutição tem a função de conduzir o conteúdo da cavidade oral, como saliva, líquidos, alimentos e medicamentos até o estômago. É uma ação complexa, que depende da integridade das vias neuronais, do sistema ósseo, muscular e articular, além do comando voluntário e da intenção de se alimentar (Mistry, Handy, 2008;Society for Neuroscience, 2018;Kamarunas, 2018).…”