Cerebral cortical processing of swallowing in older adults

Abstract

While brain-imaging studies in young adults have implicated multiple cortical regions in swallowing, investigations in older subjects are lacking. This study examined the neural representations of voluntary saliva swallowing and water swallowing in older adults. Nine healthy females were examined with event-related functional magnetic resonance imaging (fMRI) while laryngeal swallow-related movements were recorded. Swallowing in the older adults, like young adults, activated multiple cortical regions, most prominently the lateral pericentral, perisylvian, and anterior cingulate cortex. Activation of the postcentral gyrus was lateralized to the left hemisphere for saliva and water swallowing, consistent with our findings in young female subjects. Comparison of saliva and water swallowing revealed a fourfold increase in the brain volume activated by the water swallow compared to the saliva swallow, particularly within the right premotor and prefrontal cortex. This task-specific activation pattern may represent a compensatory response to the demands of the water swallow in the face of age-related diminution of oral sensorimotor function.

Normal Swallowing and Functional Magnetic Resonance Imaging: A Systematic Review

“…Six studies in this review used only event-related designs [54,55,57,59,60,65]. Two additional studies used both block and event-related designs to compare and contrast the two data acquisition methods during swallowing [53,56].…”

“…Visual cues were provided using written instructions, drawings, or even flashlight [41,53,54,60,65] and auditory cues were typically instructions given by the investigator [64]. Some studies used subject selfinfusion of a water bolus as a swallow stimulus [55] or varied the stimulus depending on the task [57,58,[61][62][63] (i.e., saliva swallow used an audio cue and water swallow was initiated by water infusion).…”

“…These techniques primarily included surface electromyography (EMG) under the chin and/or on the neck to detect movement of the muscles of the larynx [57,[61][62][63] or MR-compatible bellows to measure movement of the larynx and the thoracic cavity (respiration) [54,59,60,65].…”

“…These areas of focus include cortical [41,53,54,56,61,63], cortical and subcortical [55,57,59,60,62,65], lower brain stem and cervical spinal cord regions [58], and the cerebellum and basal ganglia [64].…”

“…The relevant studies in this review that provided age data had an average age of 35 years. Only one study focused on the swallowing neurophysiology of older adults [54]. These pioneering studies of normal swallowing using fMRI included primarily younger individuals, probably because of increased procedure tolerance and homogeneity, reducing intersubject variability that can arise by including both young and elderly individuals.…”