Charlotte Rosso1, Vincent Perlbarg2, Romain Valabregue3, Mickaël Obadia4, Claire Kemlin-Méchin5, Eric Moulton5, Sara Leder6, Sabine Meunier5, Jean-Charles Lamy3. 1. Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France; AP-HP, Urgences Cérébro-Vasculaires, Hôpital Pitié-Salpêtrière, F-75013, Paris, France. Electronic address: charlotte.rosso@gmail.com. 2. Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France; Sorbonne Universités, UPMC Univ Paris 06, CNRS, INSERM, Laboratoire d'imagerie biomédicale (LIB), F-75013, Paris, France; Bioinformatics and Biostatistics Core Facility, iCONICS, IHU-A-ICM, Institut du Cerveau et de la Moelle épinière, Paris, France. 3. Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France; Centre de Neuro-imagerie de Recherche, CENIR, F-75013, Paris, France. 4. Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France; AP-HP, Urgences Cérébro-Vasculaires, Hôpital Pitié-Salpêtrière, F-75013, Paris, France. 5. Inserm U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, Institut du Cerveau et de la Moelle épinière, ICM, F-75013, Paris, France. 6. AP-HP, Urgences Cérébro-Vasculaires, Hôpital Pitié-Salpêtrière, F-75013, Paris, France.
Abstract
BACKGROUND: Resting Motor threshold (rMT) provides information about cortical motor excitability. Interestingly, the influences of the structural or functional variability of the motor system on the rMT inter-individual variability have been poorly investigated. OBJECTIVE/HYPOTHESIS: To investigate relationships between rMT and measures of brain structures and function of the motor system. The hypothesis is that cortical excitability not only depends on the primary motor cortex (M1) but also on the integration of information originating from its vicinity such as premotor (PMd and SMA) and post-central (S1) cortices. METHODS: We measured brain structures, including grey and white matter properties (cortical volume and fiber coherence respectively), and functional interaction (resting-state functional connectivity-FC) in areas contributing to the corticospinal tract axons, i. e, M1, S1, SMA and PMd in the dominant hemisphere of 21 healthy subjects. RESULTS: The rMT was inversely correlated with the FC between PMd and M1 (r = -0.496, 95%CI: -0.764; -0.081; p = 0.02) and the grey matter volume of the dominant hemisphere (r = -0.463, 95%CI: -0.746; -0.039; p = 0.03). The multiple regression analysis model retained the FC between M1 and PMd (coefficient: -25 ± 9) as well as the grey matter volume of the dominant hemisphere (coefficient: -0.15 ± 0.06) explaining 44% of the variance of the rMT (p: 0.005). When adding age and coil-to-cortex distance, two factors known to influence rMT, the model reached a R2 of 75% (p: 0.0001). CONCLUSIONS: These results underline the major role of the PMd and the cortico-cortical connections toward M1 in the excitation of the corticospinal fibers likely through trans-synaptic pathways.
BACKGROUND: Resting Motor threshold (rMT) provides information about cortical motor excitability. Interestingly, the influences of the structural or functional variability of the motor system on the rMT inter-individual variability have been poorly investigated. OBJECTIVE/HYPOTHESIS: To investigate relationships between rMT and measures of brain structures and function of the motor system. The hypothesis is that cortical excitability not only depends on the primary motor cortex (M1) but also on the integration of information originating from its vicinity such as premotor (PMd and SMA) and post-central (S1) cortices. METHODS: We measured brain structures, including grey and white matter properties (cortical volume and fiber coherence respectively), and functional interaction (resting-state functional connectivity-FC) in areas contributing to the corticospinal tract axons, i. e, M1, S1, SMA and PMd in the dominant hemisphere of 21 healthy subjects. RESULTS: The rMT was inversely correlated with the FC between PMd and M1 (r = -0.496, 95%CI: -0.764; -0.081; p = 0.02) and the grey matter volume of the dominant hemisphere (r = -0.463, 95%CI: -0.746; -0.039; p = 0.03). The multiple regression analysis model retained the FC between M1 and PMd (coefficient: -25 ± 9) as well as the grey matter volume of the dominant hemisphere (coefficient: -0.15 ± 0.06) explaining 44% of the variance of the rMT (p: 0.005). When adding age and coil-to-cortex distance, two factors known to influence rMT, the model reached a R2 of 75% (p: 0.0001). CONCLUSIONS: These results underline the major role of the PMd and the cortico-cortical connections toward M1 in the excitation of the corticospinal fibers likely through trans-synaptic pathways.
Authors: Fiona M Baumer; Kristina Pfeifer; Adam Fogarty; Dalia Pena-Solorzano; Camarin E Rolle; Joanna L Wallace; Alexander Rotenberg; Robert S Fisher Journal: J Clin Neurophysiol Date: 2020-03 Impact factor: 2.590