Poster No:
182
Submission Type:
Abstract Submission
Authors:
Paige Howell1, Finn Rabe2, Simon Schading3, Harshal Sonar4, Jamie Paik4, Patrick Freund5, Nicole Wenderoth1, Sanne Kikkert2
Institutions:
1ETH Zürich, Zürich, Zürich, 2ETH Zürich, Zürich, Switzerland, 3Spinal Cord Injury Center Balgrist, University of Zürich, Zürich, Switzerland, 4École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland, 5Spinal Cord Injury Center Balgrist, University of Zürich, Zürich, Zürich
First Author:
Co-Author(s):
Simon Schading
Spinal Cord Injury Center Balgrist, University of Zürich
Zürich, Switzerland
Harshal Sonar
École Polytechnique Fédérale de Lausanne
Lausanne, Switzerland
Jamie Paik
École Polytechnique Fédérale de Lausanne
Lausanne, Switzerland
Patrick Freund
Spinal Cord Injury Center Balgrist, University of Zürich
Zürich, Zürich
Introduction:
Following tetraplegia (i.e., cervical spinal cord injury; SCI), individuals experience a loss of muscle function and sensation in their limbs and torso. Seminal non-human primate studies demonstrated that this leads to extensive reorganisation in brain areas containing detailed map-like body representations (e.g., the primary somatosensory cortex; S1), such that the cortical area deprived of sensory inputs (e.g., of the hand) becomes responsive to touch on intact body parts (e.g., of the face; Reed et al., 2016)). While animal models of SCI have consistently revealed reorganisation in S1, the degree and pattern of cortical remapping in humans following SCI is less clear (Jutzeler et al., 2015; Makin et al., 2015; Makin & Bensmaia, 2017). There are several potential reasons for the apparent divergence of reorganisation results in non-human primates and humans: Firstly, while work in non-human primates showed chin-to-hand area reorganisation in S1, research in humans has primarily explored lip-to-face area reorganisation. Second, non-human primate research made use of tactile stimulation protocols, while human reorganisation research typically made use of movement paradigms due to the difficulty of providing tactile face stimulation inside an MRI. Lastly, while the S1 face representation is inverted in non-human primates with the chin neighbouring the hand area (Kaas, 1983), we (Kikkert et al., 2023), and others (Root et al., 2022), have shown that in human S1 the forehead is least distance to the hand representation. In this study, we attempt to tackle these methodological differences and uncover the full architecture of S1 face reorganisation in human tetraplegic patients. We used fMRI during tactile stimulation of the forehead, lips, and chin to characterize S1 face-to-hand reorganisation in detail in tetraplegic patients.
Methods:
Suprathreshold vibrotactile stimulation was applied to the forehead, lips, cheek, and thumb of 16 chronic tetraplegic patients and 21 healthy control participants while they underwent 3T fMRI. The patient sample was heterogeneous in neurological level of injury (C1-C7), severity of neurological loss (ASIA A-D), and retained hand functioning (GRASSP score 22-188, healthy score = 232). Tactile stimulation was provided in a blocked-design fashion using an in-house build MRI-compatible pneumatic stimulator device that we previously validated for use in somatotopic mapping fMRI experiments (Kikkert et al., 2023; Sonar et al., 2021; Sonar & Paik, 2016). To uncover reorganisation, we first assessed the level of forehead, lips, and chin activity in an anatomical S1 hand area. We further assessed potential cortical shifts by extraction the geodesic distance of the peak S1 forehead, lips, and chin activity from an S1 foot area anchor.
Results:
Our results did not show any differences in level of face parts activity in the S1 hand area between control participants and tetraplegic patients (p > 0.51; BF10 < 0.38), nor any representational shifts of the forehead, lips, or chin (p > 0.73; BF10 < 0.34). We did not find any significant correlations between our indicators of reorganisation and patients' retained hand functioning, time since injury, or anatomically defined amount of tissue bridges at the level of the spinal injury.
Conclusions:
Our results did not show evidence for face-to-hand area reorganisation in S1 of human tetraplegic patients. Given that we aimed to match our approaches to those used in classical non-human primates experiments demonstrating face reorganisation, we suggest that face reorganisation is not apparent in humans. Future experiments that use intracortical recording methods (as in non-human primate studies) are needed.
Disorders of the Nervous System:
Neurodegenerative/ Late Life (eg. Parkinson’s, Alzheimer’s) 1
Perception, Attention and Motor Behavior:
Perception: Tactile/Somatosensory 2
Keywords:
FUNCTIONAL MRI
Plasticity
Somatosensory
Other - spinal cord injury; somatotopy; reorganisation; tetraplegia
1|2Indicates the priority used for review
Provide references using author date format
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Kaas, J. H. (1983). What, if anything, is SI? Organization of first somatosensory area of cortex. Physiological Reviews, 63(1), 206–231.
Kikkert, S., Sonar, H. A., Freund, P., Paik, J., & Wenderoth, N. (2023). Hand and face somatotopy shown using MRI-safe vibrotactile stimulation with a novel soft pneumatic actuator (SPA)-skin interface. NeuroImage, 269. https://doi.org/10.1016/j.neuroimage.2023.119932
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