## 2 Materials and Methods
### fMRI Standard Procedure  
All 24 subjects participated in an 18-min total time functional imaging run during a single experimental session, while laying supine. The functional run was composed of 2 different \"cortical\" activation tasks, each lasting 9 min, and these were performed in a controlled order: first 12 participants with (1) Tongue Protrusion; (2) Tongue Elevation and then 12 participants with (1) Tongue Elevation; (2) Tongue Protrusion. Each task had a duration of 30 s, similar to the timing protocol by [PERSON] et al. (2001) [45]. The rationale for each task being 30 s is that a functional resonance of a just a few seconds on 4 mm thick slices would not be enough to have accurate information [15; 16]. Moreover, the subjects were instructed to swallow accumulated saliva, which requires some time to naturally be produced and although healthy subjects could swallow between 3 and 7 times in 30 s ([PERSON] et al. 2015), [46]. We felt that not imposing the additional strain of producing multiple saliva swallows would give us a better reading. A physiological swallow lasts between 1 s and 1.5 s, depending on many factors, including the viscosity of saliva or food [2; 3; 47] and [PERSON], 2008; [48] [PERSON] JA [49]. Therefore, the rationale for longer preparation times (compared to the time needed to swallow a few seconds) is linked to the type of investigation and refers to the time required from each patient to obtain the recording of three-dimensional images acquired at a rate every 2 or 3 s. To be sure of havingmore precise information it is necessary to acquire hundreds of images and for this reason we settled on 30 s intervals. For brain structures, the thickness of 4 mm instead of 2 mm is the right compromise to have a greater number of point of data acquisitions, reduced noise, and therefore a reduction of the artifacts and an increase in the image quality. Furthermore, taking a greater thickness during functional resonance test generates a greater number of ossiHb which contributes to the signal from each layer further improving the quality of the exam. Taking 2 mm slices would have reduced these outcomes, hence the choice of 4 mm. For brain structures, the thickness of 4 mm was deemed to be the appropriate choice to have a greater number of point of data acquisitions, reduced noise, and therefore a reduction of the artifacts and an increase in the image quality. Furthermore, taking a greater thickness during functional resonance test generates a greater number of ossiHb, which contributes to the signal from each layer further improving the quality of the exam. Taking 2 mm slices would have reduced these outcomes, hence the choice of 4 mm, chosen by the radiologist who performed this examination based on his professional experience. Furthermore, a study on functional magnetic resonance confirms that unlike magnetic resonance, the thickness of 4 mm is recommended [14; 49; 50]. Task switching was indicated using acoustic cues at the beginning and end of each block of tasks or rest. Participants were instructed just before each task, in order to correctly perform the tasks. The swallowing had to be performed only once for each task, without exaggerating any oral movements. (Figure 1). The issue arose that the first task sequence could influence the cerebral effect of the second, but we could not find publications on the subject to offer a reasonable guidance. Moreover, it was considered that in order to have a sufficiently long wash-out period (time needed for the cerebral effect of the first sequence to wear off), we would have needed to perform two fMRI sessions, triggering concerts about its ethical justification and economic sustainability. Therefore, we considered our choice as guided by clinical experience, since we were lacking peer-reviewed guidance. Our choice could guide future studies in considering more appropriate ways to eliminate unwanted side effects that could bias the outcomes.