Motor memory interference

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Motor learning is the process of improving the performance of motor skills through motor practice. Practice is essential for learning motor skills because it is during practice that the nervous system encodes the sensorimotor information, which is used for the elaboration of motor memories. However, the nervous system does not stop processing information with the end of practice. After practicing a motor task (A), the information encoded during practice is consolidated within the brain as a form of motor memory. If consolidation is successful, the memory encoded during the practice of A becomes more stable, leading to the retention of A or even to further improvements in skill performance between practice sessions without additional training. During the initial stages of consolidation, however, motor memories are still fragile and if a second motor task (B) is practiced soon after, memory interference may occur. The performance of B may result in two types of interference: retrograde and anterograde interference. Retrograde interference occurs when the practice of B disrupts the consolidation of A and anterograde interference when the practice of B impairs the performance of A at retention. When interference occurs, memories do not consolidate properly and the retention of previous learning (A) is compromised. Memory interference is a useful experimental tool to investigate memory formation processes because it allows to test the strength of a memory trace during its consolidation, however, its underlying mechanisms are not well understood. The short term objective of my research program is to conduct 4 studies that use memory interference paradigms applied through behavioural and non-invasive brain stimulation techniques to discover neurophysiological mechanisms underlying memory interference in the context of healthy aging. Study 1 explores if the coupling between cortico-spinal neurons changes as a result of retrograde and anterograde interference. Study 2 investigates if the susceptibility to interference of the primary motor cortex signals the pace of memory consolidation. Study 3 explores if the inhibition of brain networks involved in processing different types of memory modifies the susceptibility to interference between different memory systems. Study 4 investigates if long term potentiation, a substrate of memory formation, predicts interference. The long term goal of my research program is to create a novel framework to explain memory interference. This framework argues that interference arises as the competition for neural networks and resources between the primary (A) and interfering tasks (B). When no overlap between memory representations exists and 2 independent neuronal pools are elicited, both memory traces can be consolidated in parallel and interference does not occur. In contrast, when consolidation requires the same pool of synapses, interference occurs.    **