Early motor skill acquisition in healthy older adults: functional MRI and connectome correlates

decrement have been proposed, such as weakened acquisition of the motor skill. While the processes at play during the initial acquisition phase have been well-characterized in young adults, they were only scarcely investigated in older adults. The goal of this thesis was to assess the neural processes occurring during the acquisition phase of motor learning in older adults. Successful functioning of the brain is complex and relies on complementary types of organization, i.e. the principles of segregation and integration. In other words, the brain is composed of segregated and specialized brain regions that interact with each other by exchanging information. Motor learning, considered as a key function of the brain, does not deviate from this organization scheme. As such, the investigation of motor learning beneficiates from the study of both functional segregation and integration. The results of this thesis are based on the acquired data of a multiple-day experiment aiming at characterizing motor learning acquisition and improving sleep-dependent motor memory consolidation in older adults and stroke patients. 43 older adults and 15 stroke patients were included in this project and completed multiple measurements involving, among other methods, a novel motor learning task performed concurrently with func-tional magnetic resonance imaging. In the first study of this thesis, we examined the functional specialization of the brain during acquisition of the motor skill by investigating the within-session dynamics and their relationship with behavioral change. The results demonstrated that motor learning ability relied on the parallel involvement of motor-related cortical areas responsible for action selection and associative parietal areas involved in visuomotor processing. In the second study of this thesis, we assessed the integration of information transfer within functional subnetworks by looking at the changes in functional topology and structure-function correspondence in relation to motor learning ability. We were able to show that motor learning ability was associated with higher flexibility in visual and cognitive/associative networks suggested by increased modularity of the functional subnetworks and a detachment of the functional connectome from the structural connectome. In conclusion, this thesis demonstrates that the acquisition of a motor skill in healthy aging relies on the in-volvement and flexibility of distributed brain regions organized in networks. The achieved results expand on the existing knowledge of motor learning and offer an indication that multimodal studies are important to comprehend the functional processes of the brain.