Exploring the Role of Muscle Proprioception in Kinesthesia and Spinal Proprio-Motor Circuits via fMRI: From Fundamental to Clinical Perspectives

When : at 2:00 PM 

Where : in the Charve Amphitheater (Building 9, Saint-Charles campus). 

The defense will be conducted in English.

A Zoom link is provided at the end of this email for those unable to attend in person.

Multisense & Body team - Centre de Recherche en Psychologie et Neurosciences (CRPN, UMR7077)

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Composition of the Jury :
Dimitri Van De Ville (École Polytechnique Fédérale de Lausanne) - Thesis Reviewer
Pavel Lindberg (Université de Paris) - Thesis Reviewer
Virginie Callot (Université Aix-Marseille) - Jury President
Anne Kavounoudias (Université Aix-Marseille) - Thesis Director
Julien Cohen-Adad (Université de Montréal) - Invited Member

Short Abstract: Muscle proprioception, often called the "sixth sense," allows us to perceive the position and movement of our body in space. This sense depends on specialized receptors within muscles that detect stretch and relay this information to the brain. By using muscle tendon vibration, we can elicit illusions of movement without any actual motion. Our research shows that these illusions become even clearer when combining proprioceptive input with visual cues, thanks to visuo-proprioceptive integration. Using spinal fMRI, we explored how these signals are processed in the spinal cord, and observed specific neural circuits in line with myotome maps, and that adapt after proprioceptive training. These findings open new doors for improving rehabilitation in patients recovering from strokes or amputations, suggesting that integrating multisensory approaches with advanced tools like spinal fMRI could significantly enhance recovery outcomes.

Full Abstract: Muscle proprioception, often referred to as the "sixth sense," enables the perception of one’s body position and movement in space. It relies on afferent fibers wrapped around the intrafusal fibers of muscle spindles, which detect muscle stretch and are essential for perceiving movement, or kinesthesia. These perceptions can be manipulated through mechanical tendon vibration, which selectively stimulates proprioceptive Ia afferents, giving rise to kinesthetic illusions of muscle elongation without actual movement. Vision also plays a key role in movement perception, as seen in the mirror box paradigm, a rehabilitation technique that uses visual feedback to create the illusion of movement in a paralyzed or missing limb. However, the efficiency of this method is still debated, possibly due to lack of concurrent proprioceptive feedback. A growing body of evidence highlights the benefits of optimal processing of multisensory integration in enhancing perceptual reliability and accuracy.
In the first part of this work, we studied the effects of adding proprioceptive stimulation to the mirror box paradigm to assess whether multisensory integration occurred and could be leveraged for rehabilitation purposes. Our study demonstrated that proprioceptive input alone produced clearer illusions than visual input and combining both visual and proprioceptive stimuli enhanced strength and clarity of illusions. These findings suggest the potential of visuo-proprioceptive integration for improving lower limb rehabilitation in stroke or amputated patients [Schlienger et al., 2023].
While central proprioceptive and multisensory integration has been well studied at the brain level, its mechanisms at the spinal level are less understood. The complex network of sensory inputs, interneurons, and motor neurons within the spinal cord has been anatomically evidenced by cadaver studies and its functional organization has been explored via clinical cases, invasive epidural electrical stimulation and, to a lesser extent, electrophysiology. Over the past decade, spinal functional Magnetic Resonance Imaging (fMRI) has overcome significant technical challenges, and has since emerged as a reliable, non-invasive tool, opening new possibilities for spinal research, where many questions remain.
In the second part of this thesis, we conducted two innovative studies in healthy adults to explore proprioceptive circuitsusing spinal fMRI in combination with muscle tendon vibration. By examining several muscle groups in the upper and lower limbs, we identified distinct patterns of in-plane and rostrocaudal organization depending on the stimulated muscle and body site. These findings mostly align with established myotome maps accounting for broad overlaps, plural innervation and asymmetry, but also reveal substantial individual variability. At the cervical level, a novel tool was developed through international collaboration to individualize analyses and improve precision of functional activation localization [Valošek et al., 2024]. We further explored spinal plasticity at the lumbar cord, observing increased activation after two weeks of proprioceptive training, particularly in levels associated with the targeted muscles.
In conclusion, this work emphasizes the importance of muscle proprioceptive information in kinesthetic perception and the benefits of integrating it with other sensory inputs such as vision for rehabilitation. It also provides new insights into spinal sensorimotor circuits, showing that they can be studied non-invasively and longitudinally using spinal fMRI. Mastering spinal fMRI to explore spinal circuit organization and modulation is a promising research avenue for clinical use. As the technique improves with advanced acquisition and analysis tools driven by a growing research community, it is expected to have significant clinical impact.