L'apprentissage moteur auprès de populations avec déficits sensoriel et moteur

Learning new motor skills is essential to the human experience and to the performance of everyday activities. Motor learning can be defined as a set of processes associated with practice or experience leading to the ability to skillfully perform a new motor skill. At the root of these learning mechanisms, precise motor control and adequate sensorimotor integration are critical. Additionally, the ability to identify a sequence in serial events and accurately reproduce the series of detected movements is also important with regards to learning motor sequences that are present in many human behaviors. If any of these fundamental processes are compromised by any pathology, one can expect to observe difficulties in learning different motor skills.    The studies that compose the present thesis had as a main objective to characterize the motor learning abilities in two clinical populations presenting a sensory or motor abnormality with the serial reaction time task (SRTT). In article 1, the consequences of hearing impairment on motor learning were investigated. Few studies have examined motor capacities in the profoundly deaf and these studies have suggested the presence of deficits in manual dexterity and delays in movement production. Before the publication of this article, the ability to learn complex sequential motor patterns had not been explored in a deaf adult population. Non-specific and sequence-specific learning on the SRTT were analyzed in relation to individual features related to the hearing loss. The results revealed significant differences between groups in sequence-specific learning, with deaf subjects being less efficient than controls in acquiring sequence-specific knowledge. We interpreted the results in light of cross-modal plasticity and the auditory scaffolding hypothesis. In article 2, motor learning, intermanual transfer of a newly acquired motor skill and activity-dependent modulation of electrophysiological motor overflow (physiological mirror movements; pMM) were assessed in a large, four-generational family with a Deleted in Colorectal Cancer (DCC) gene mutation and congenital mirror movements (CMM). CMM are involuntary muscle contractions in the opposite side of the body occurring during voluntary unilateral movement. They have been associated with a frameshift mutation in the DCC gene, resulting in abnormal corticospinal tracts and reduced interhemispheric inhibition (IHI). Compared with family members without CMM and unrelated healthy controls, pMM were significantly increased in CMM individuals following execution of the SRTT. Motor learning and intermanual transfer did not differ between groups. However, when participants with the DCC mutation, with or without CMM, were compared with participants without the DCC mutation, non-specific learning of a motor sequence was significantly reduced in individuals with the DCC mutation. These data suggest that increased physiological mirroring in CMM patients is associated with reduced IHI. Furthermore, impairments in non-specific motor learning in DCC mutation carriers may be related to the reported alterations in cerebellar activity and connectivity. In summary, the studies comprised in the present thesis significantly increase our knowledge of motor learning abilities in the contexts of sensory or motor deficits.

Keyphrases: Motor learning, Hearing impairment, Deafness, Mirror movements, Congenital mirror movements, SRTT, Interhemispheric inhibition, DCC gene