Table 1.
| Author, Date | N | Age (range and/or avg.) | Design (fMRI) | Brain Location Focus | Task(s) | Stimuli | Plane of Image Acqui-sition | Swallowing monitoring | Results: Location of voxel activation (Swallowing Tasks only, group data) |
|---|---|---|---|---|---|---|---|---|---|
| Birn, 1999 | 6 | not reported | block and event-related | Cortical | (1)speaking out loud
(2)swallowing (saliva) (3)jaw clenching (4)tongue movement (5)finger-tapping |
visual (cued by flash light) | axial | none reported | motor cortex |
| Hamdy, 1999 | 10 | 32 avg. 22–61 yrs | event-related | cortical, subcortical | 20 wet swallows (water-infused bolus) | water infusion | axial | pneumographic belt | anterorostral cingulate cortex, caudolateral sensorimotor cortex, anterior insula, frontal opercular cortex, superior premotor cortex, anteriomedial temporal cortex, and precuneus. |
| Mosier, 1999a | 8 | 34 avg. | block | Cortical | (1) 10 sec saliva swallow
(2) 10 sec wet swallow (3) 15 sec saliva swallow, (4) finger tap |
“instructed” and self-infusion of water | axial and coronal | EMG | 10- and 15-second tasks: bilateral primary motor cortex (mid precentral gyrus) in all subjects. Activity also identified in primary somatosensory cortex, supplementary motor cortex, prefrontal cortex, transverse temporal gyrus, insular cortex, internal capsule |
| Mosier, 1999b | 8 | 39 avg. | block | cortical, subcortical | (1) 10 sec saliva swallow
(2) 10 sec water swallow (3) 15 sec saliva swallow, (4) finger tap |
audio and self-infusion of water | axial and coronal | EMG | 10- and 15-second tasks: primary motor cortex bilaterally in all subjects. Activation also in primary somatosensory cortex, supplementary motor area, prefrontal cortex, superior temporal gyrus, insular cortex, transverse temporal gyrus, cingulate gyrus, association areas, sensori-motor integration areas, thalamus, and internal capsule |
| Kern, 2001a | 8 | 24–27 yrs | event-related | cortical, subcortical | (1) volitional swallow
(2) relfexive swallow |
tap on the leg (vol. swallow) and infusion of water (reflx. swallow) | sagittal | EMG | Reflexive: bilateral activity in primary sensory and motor regions Volitional: bilateral activity in primary sensory and motor regions as well as insula, prefrontal, anterior cingulate, and parieto occipital regions |
| Kern, 2001b | 10 | 21–42 yrs | block and event-related | Cortical | (1) lip pursing (2) tongue rolling (3) jaw clenching (4) volitional swallow (saliva) | tap on the leg | axial and sagital | none reported | anterior cingulate, motor/premotor cortex, insula, occipital/parietal region |
| Martin, 2001 | 14 | 28 avg. 22–34 yrs | event-related | cortical, subcortical | (1 )naïve swallow (sbj unaware that swallowing being tested)
(2) voluntary (saliva) (3) swallow (water) |
“instructed” (voluntary saliva and water) | axial, coronal and sagittal | MR-compatible bellows (larynx) | Naïve, voluntary and water: lateral precentral gyrus, lateral post-central gyrus, right insula. Caudal anterior cingulate cortex activated with voluntary and water swallows sigificantly more than naïve swallows. |
| Mosier, 2001 | 8 | not provided | block | cortical networks | (1) 10 sec saliva swallow
(2) 10 sec wet swallow (3) 15 sec saliva swallow, (4) finger tap |
audio and self-infusion of water | axial and coronal | EMG | Activation in the sensorimotor cortices, cingulate, premotor cortex, parietal cortex, temporal cortex, basal ganglia and thalamus, insula, and cerebellum. Activation in these areas were not statistically different among tasks. |
| Fraser, 2002 | 8 | 26 avg. 23–34 yrs | block | Cortical | (1) swallow (water bolus) “on-period” (2) no swallowing “off period” (both tasks occurred after pharyngeal stimulation and sham) | visual | axial | none reported | Sensory and motor cortices had significantly increased voxel activation with pharyngeal stimulation compared to no-stimulation (p = 0.047) |
| Komisaruk, 2002 | 7 | 22–57 yrs | block | lower brainstem and cervical spinal cord regions | (1) tongue tapping
(2) smile-pucker (3) gaze shifting (4) face brushing (5) finger tapping (6) swallow (saliva and Mendelsohn maneuver) (7) taste |
“instructed” | coronal and sagittal | none reported | The nucleus ambiguus was activated 78% of the time during Mendelsohn maneuver (swallow with prolonged laryngeal elevation) and the inferolateral aspect of the motor cortex, just superior to the lateral sulcus (homuncular pharyngeal region) was also active. |
| Suzuki, 2003 | 11 | 24–42 yrs | block | Cerebellum and basal ganglia | (1) swallow (saliva)
(2) no swallow |
auditory | axial, coronal and sagittal | none reported | Precentral and postcentral gyri, insular gyrus, cerebellum, putamen, globus pallidus across subjects. All bilat except for cerbellum. |
| Martin, 2004 | 14 | 28 avg. 22–35 yrs | event-related | cortical, subcortical | (1) voluntary swallow (saliva) (2) voluntary tongue elevation (3) voluntary finger opposition. | visual | axial, coronal and sagittal | MR-compatible bellows (larynx and tongue) | Largest voxel activation: lat postcentral gyrus, parietal opeculum, supramarginal gyrus (left hem only). Secondary prominent areas: anterior cingulated cortex and supplementary motor area. |
| Toogood, 2005 | 8 | 23.8 avg. 22–26 yrs | event-related | cortical, subcortical | (1) swallow (saliva, “Go”/“do swallow” condition)
(2) relax, don’t swallow (during “No Go”/“don’t swallow” condition) |
visual | sagittal | MR-compatible bellows (larynx and resp) | Significantly more activated voxels for “Do swallow” in precentral gyrus (p = 0.01), postcentral gyrus (p = 0.02), anterior cingulated cortex corresponding to BA24 (p = 0.04) and corresponding to BA32 (p = 0.03). More active voxels in insula/operculum in “Do” condition, but not significant. |
| Martin, 2006 | 9 | 74.2 avg. 66–82 yrs | event-related | cortical | (1) saliva swallow
(2) water swallow (3ml) |
visual | axial | MR-compatible bellows (larynx) | Saliva Swallow: strong activation in the left pericentral cortex (including perisylvian, primary motor and sensory cortices). Some right pre- and post-central activity. Also prominent were right supplementary motor area, anterior cingulate cortex, superior and middle frontal gyri, inferior parietal lobule, and left insula/operculum. Less activity in left putamen and thalamus, precuneus/cuneus, lingual gyrus, and fusiform gyrus. |
| Water Swallow: largest activation in blateral superior and middle frontal gyri, followed by pericentral cortex. Also prominent were left supplementary motor area, anterior cingulate cortex, and inferior parietal lobule. Activation also observed in thalamus, precuneus/cuneus, right middle occipital gyrus, and lingual gyrus |