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Cognition, Action, and sensorimotor plasticity

I-SITE Neural Plasticity and Mental Actions

Project : I-Site Neural Plasticity and Mental Actions
Principal investigator : Florent Lebon, Associate Professor
Grant program : Junior Fellowship

The current proposal, entitled « Neural Plasticity and Mental Actions », is part of the three main domains defined by ISITE-BFC: Soins individualisés et intégrés. This research in Cognitive and Behavioral Sciences focuses on the neural plasticity in humans induced by motor imagery. Motor imagery is the mental representation of the desired movement, without executing it.

Training by actual repetitions of the movement is an undeniable intervention for the acquisition and the consolidation of new motor abilities, such as playing piano, driving a car or performing in gymnastics1. However, it is not the unique way to learn. A well-known alternative method is mental training. This method is used by athletes, musicians or even surgeons, to improve their operating acts; it can also be used by patients to ease his/her rehabilitation.

My research proposal aims at determining the neural components at play during mental training. The goal is to explain how our system changes following such training. By means of complementary techniques, we test the implication of the different stages of our system, from the brain to the muscles, going through the spinal cord. This research is performed in the INSERM U1093 laboratory Cognition, Action and Sensorimotor Plasticity at the Dijon Sport Science Faculty.

In a first experiment, we tested a well-known model that improves motor performance: use-dependent learning. This consists in repeating the same movement to render this movement more efficient and more robust. We hypothesized that mentally repeating the same movement, without executing it, would reinforce our system and therefore change our behavior. To test this hypothesis, we used a safe and non-invasive stimulation technique: transcranial magnetic stimulation. When positioned on the scalp, the stimulation coil induces a magnetic field that stimulates the neurons of a specific area, which controls hand muscles for example. With markers positioned on the hand, we recorded the direction induced by the stimulation, when the participant was at rest. We then asked to imagine a movement in the opposite direction. For example, if the stimulation induced an extension of the hand, the participant imagined a flexion movement without moving. After the mental training, we observed that the stimulation induced hand movements towards the direction of the imagined movements. Even though the participant did not move, he/she changed the neural network that controls his/her hand. This behavioral change is explained by the reinforcement of connections between neurons going from the brain to the muscles. The findings of this study were presented at the conference of the Society for Neurosciences in November 20182 and are currently in revision in a renowned journal in the field of Neurosciences (Scientific Reports)3.

A second experiment is currently performed in the laboratory to determine which neural structures are activated during motor imagery. Since mental training consists in imagining movements without actually executing it, it is obvious to consider that everything happens within the brain. Yet, a series of experiments we performed in the lab showed that the spinal cord, which is the interface between the brain and the muscles, is also activated. The latest study4 showed that a one-week mental training changed the inhibition/activation balance at the spinal cord. As a follow-up, Cécilia Neige, a post-doctorate fellow in the laboratory, currently performs a study to identify the importance of inhibitory processes for performance improvements following mental training. A first series of experiment validated the methods to measure inhibition within the motor cortex. The findings are currently in preparation for publication in a methodological journal5. We are now entering the training phase. Thirty participants will be recruited to follow a mental training program (or a placebo training) of 2 weeks, with 5 training sessions per week. The aim is to confirm the strength increase after mental training and to assess the inhibitory mechanisms that explain such performance improvement. By means of complementary techniques, we will measure the activity of the brain, the spinal cord and the muscles. We hypothesized that the strength increase would be accompanied by a decrease in inhibition within the brain and the spinal cord. We expect that the greater the inhibitory decrease, the greater the strength increase.

References
1. Robertson EM, Pascual-Leone A, Miall RC (2004) Current concepts in procedural consolidation. Nat Rev Neurosci 5:576–582.
2. Lebon F., Ruffino C., Gaveau J. & Papaxanthis C. Use-dependent learning is subject to corticospinal excitability: data from motor imagery and motor preparation. Society for Neuroscience Conference, San Diego, CA, USA. 03 – 07 Novembre 2018
3. Ruffino C., Gaveau J., Papaxanthis C, & Lebon F. An acute session of motor imagery training induces use-dependent plasticity. Scientific Reports, in revision. 4. Grosprêtre S., Lebon F., Papaxanthis C., & Martin A. (2016) New evidence of cortico-spinal network modulation induced by motor imagery. Journal of Neurophysiology, 115, 1279-1288.
5. Neige C., Martin A., Grosprêtre S., & Lebon F. Effect of M-wave consideration in the normalization of the short interval intracortical inhibition during muscle contractions. In preparation for Journal of Neurophysiology.

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