Abstract
In the present multiple case study, we examined hemodynamic changes in the brain in response to motor execution (ME) and motor imagery (MI) of swallowing in dysphagia patients compared to healthy matched controls using near-infrared spectroscopy (NIRS). Two stroke patients with cerebral lesions in the right hemisphere, two stroke patients with lesions in the brainstem, and two neurologically healthy control subjects actively swallowed saliva (ME) and mentally imagined to swallow saliva (MI) in a randomized order while changes in concentration of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) were assessed. In line with recent findings in healthy young adults, MI and ME of swallowing led to the strongest NIRS signal change in the inferior frontal gyrus in stroke patients as well as in healthy elderly. We found differences in the topographical distribution and time course of the hemodynamic response in dependence on lesion location. Dysphagia patients with lesions in the brainstem showed bilateral hemodynamic signal changes in the inferior frontal gyrus during active swallowing comparable to healthy controls. In contrast, dysphagia patients with cerebral lesions in the right hemisphere showed more unilateral activation patterns during swallowing. Furthermore, patients with cerebral lesions showed a prolonged time course of the hemodynamic response during MI and ME of swallowing compared to healthy controls and patients with brainstem lesions. Brain activation patterns associated with ME and MI of swallowing were largely comparable, especially for changes in deoxy-Hb. Hence, the present results provide new evidence regarding timing and topographical distribution of the hemodynamic response during ME and MI of swallowing in dysphagia patients and may have practical impact on future dysphagia treatment.
Highlights
Dysphagia is a difficulty in swallowing that often occurs in neurological patients [1]
In a recent study performed in our lab, we investigated brain activation patterns associated with motor execution (ME) and mental imagery of swallowing in healthy young adults using near-infrared spectroscopy (NIRS)
To identify the NIRS channels that showed the strongest NIRS signal change during ME/motor imagery (MI) of swallowing compared to the baseline interval in each individual participant, we used the false discovery rate (FDR) method to control the proportion of false positives among the channels that are detected as significant [60]
Summary
Dysphagia is a difficulty in swallowing that often occurs in neurological patients [1]. We aimed at identifying brain correlates of active swallowing and mental imagination of swallowing in single stroke patients with dysphagia compared to healthy matched controls, which might be the basis for upcoming dysphagia rehabilitation [5]. Brain activation patterns associated with mental imagination of swallowing have been scarcely investigated. In a recent study performed in our lab, we investigated brain activation patterns associated with ME and mental imagery of swallowing in healthy young adults using near-infrared spectroscopy (NIRS). We found the strongest activation during both tasks in the inferior frontal gyrus bilaterally This prior NIRS study provided first evidence that the hemodynamic response during ME and MI of swallowing is largely comparable in healthy people [5]
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