Model-Based and Model-Free Analyses of the Neural Correlates of Tongue Movements

Abstract

The tongue performs movements in all directions to subserve its diverse functions in chewing, swallowing, and speech production. Using task-based functional MRI in a group of 17 healthy young participants, we studied (1) potential differences in the cerebral control of frontal (protrusion), horizontal (side to side), and vertical (elevation) tongue movements and (2) inter-individual differences in tongue motor control. To investigate differences between different tongue movements, we performed voxel-wise multiple linear regressions. To investigate inter-individual differences, we applied a novel approach, spatio-temporal filtering of independent components. For this approach, individual functional data were decomposed into spatially independent components and corresponding time courses using independent component analysis. A temporal filter (correlation with the expected brain response) was used to identify independent components time-locked to the tongue motor tasks. A spatial filter (cross-correlation with established neurofunctional systems) was used to identify brain activity not timelocked to the tasks. Our results confirm the importance of an extended bilateral cortical and subcortical network for the control of tongue movements. Frontal (protrusion) tongue movements, highly overlearned movements related to speech production, showed less activity in the frontal and parietal lobes compared to horizontal (side to side) and vertical (elevation) movements and greater activity in the left frontal and temporal lobes compared to vertical movements (cluster-forming threshold of Z > 3.1, cluster significance threshold of p < 0.01, corrected for multiple comparisons). The investigation of inter-individual differences revealed a component representing the tongue primary sensorimotor cortex time-locked to the task in all participants. Using the spatial filter, we found the default mode network in 16 of 17 participants, the left fronto-parietal network in 16, the right fronto-parietal network in 8, and the executive control network in four participants (Pearson's r > 0.4 between neurofunctional systems and individual components). These results demonstrate that spatio-temporal filtering of independent components allows to identify individual brain activity related to a specific task and also structured spatiotemporal processes representing known neurofunctional systems on an individual basis. This novel approach may be useful for the assessment of individual patients and results may be related to individual clinical, behavioral, and genetic information.

NeuroVAD: Real-Time Voice Activity Detection from Non-Invasive Neuromagnetic Signals

“…While this analysis highlights common sensors across subjects, there is still large intersubject variability as shown in Figure 6d. This variability may speak to the high level of inter-individual variation in neuro-cognitive network structure observed in neuroimaging experiments and reflect the necessity of subject-dependent decoding [39]. Nevertheless, the efficacy of this study is in getting high accuracy in single-trial level with an average standard deviation of <10%.…”

Functional MRI of native and non-native speech production in sequential German-English bilinguals

“…The lateral primary sensori-motor cortex directly controls the muscles of the larynx (20, 21) and the articulators, including the tongue (11), and processes somatosensory information of the oral cavity (22). Although the laryngeal and oro-facial midline muscles are innervated by both hemispheres, specific speech motor plans, or articulatory gestures, are primarily represented in the left primary motor cortex (23).…”

“…This experiment was part of a larger project on oral and speech language functions. Detailed inclusion and exclusion criteria for the participants were published in a paper on the neural correlates of tongue movements (11). In brief, all participants were part of a convenience sample of students of the University of Oldenburg, Germany, without a history of neurological or psychiatric disorders or substance abuse.…”

“…After the experiment described here, three additional experiments were performed during the same imaging session, including the overt production of tongue twisters, movements of the tongue (11), and overt production of sentences 6 . The duration of the entire scanning session was approximately 45 min.…”

“…Structural and functional MR images of the entire brain were acquired on a researchonly Siemens MAGNETOM Prisma whole-body scanner at 3 Tesla (Siemens, Erlangen, Germany) and a 64-channel head/neck receive-array coil located at the Neuroimaging Unit, School of Medicine and Health Sciences, University of Oldenburg, Germany. 7 We used a T1-weighted MPRAGE sequence to acquire structural data and a T2*-weighted BOLD sequence (305 volumes, time of acquisition: 9:16 min) to acquire functional data (for details, see (11)).…”