Changes in hemodynamic signals accompanying motor imagery and motor execution of swallowing: a near-infrared spec troscopy study

In the present study we investigated hemodynamic changes in the brain in response to motor execution (ME) and motor imagery (MI) of swallowing using near-infrared spectroscopy (NIRS). Previous studies provide evidence that ME and MI of limb movements lead to comparable brain activation patterns indicating the potential value of MI for motor rehabilitation. In this context, identifying brain correlates of MI of swallowing may be potentially useful for the treatment of dysphagia. Fourteen healthy participants actively swallowed water (ME) and mentally imagined to swallow water (MI) in a randomized order while changes in concentration of oxygenated hemoglobin (oxy-Hb) and deoxygenated hemoglobin (deoxy-Hb) were assessed. MI and ME led to the strongest NIRS signal changes in the inferior frontal gyrus. During and after ME, oxy-Hb significantly increased, with a maximum peak around 15s after task onset. In contrast, oxy-Hb decreased during MI compared to a rest period probably because of motor inhibition mechanisms. Changes in deoxy-Hb were largely comparable between MI and ME, especially when participants used a kinesthetic motor imagery strategy during MI compared to no specific strategy. Hence, the present study provides new evidence concerning timing and topographical distribution of the hemodynamic response during ME and MI of swallowing.