Effect of Age on Cortical Activation during Swallowing: An fMRI Study

Abstract

Objective: Understanding the neural functional organization of swallowing in the elderly is essential when diagnosing and treating older adults with swallowing difficulties. While brain-imaging studies in young adults have implicated multiple cortical regions in swallowing, only a few investigations were performed on older subjects. In this study, we aimed to compare neural activation in regions for swallowing between healthy young and older adults and to better understand neural control of deglutition, complex sensory-motor process which occurs as a result of old age. Method: Fifteen young and fifteen older healthy individuals without a swallowing problem were examined with functional magnetic resonance imaging (fMRI) during voluntary saliva swallowing. Functional image data was obtained with a T2 gradient-echo, echo planar imaging (EPI) pulse sequence optimized for blood-oxygen level dependent (BOLD) contrast. Two samples t-test was conducted to perform group comparison (younger adults versus older adults) for the areas in which the activation was larger for the swallowing condition than the non-swallow condition. Result: Both groups showed activations in areas involved in the motor control and execution. In both groups, main regions of activation included bilateral prefrontal cortex, primary somatosensory cortex, insula, basal ganglia, and cerebellum. Between-group comparisons revealed statistically stronger activations in the prefrontal cortex and middle temporal gyrus of older adults during swallowing. Conclusion: This study provides evidence that swallowing requires larger and more widespread areas of neural control in older adults group, especially in prefrontal cortex and inferior frontal gyrus. These findings suggest that more demanding swallowing tasks are necessary for elderly patients because of their inefficient neural network due to their age.