Maxime Trempe

Distinct consolidation outcomes in a visuomotor adaptation task: Off-line leaning and persistent after-effect

Consolidation is a time-dependent process responsible for the storage of information in long-term memory. As such, it plays a crucial role in motor learning. In two experiments, we sought to determine whether ones performance influences the outcome of the consolidation process. We used a visuomotor adaptation task in which the cursor moved by the participants was rotated 30 degrees clockwise. Thus, participants had to learn a new internal model to compensate for the rotation of the visual feedback. The results indicated that when participants showed good adaptation in the first session, consolidation resulted in a persistent after-effect in a no-rotation transfer test; they had difficulty returning to their normal no-rotation internal model. However, when participants showed poor adaptation in the first session, consolidation led to significant off-line learning (between sessions improvement) but labile after-effects. These observations suggest that distinct consolidation outcomes (off-line learning and persistent after-effect) may occur depending on the learners initial performance.

Straight ahead acts as a reference for visuomotor adaptation

One can adapt movement planning to compensate for a mismatch between vision and action. Previous research with prismatic lenses has shown this adaptation to be accompanied with a shift in the evaluation of one’s body midline, suggesting an important role of this reference for successful adaptation. This interpretation leads to the prediction that rotation adaptation could be more difficult to learn for some directions than others. Specifically, we hypothesized that targets seen to the right of the body midline but for which a rotation imposes a movement to its left would generate a conflict leading to a bias in movement planning. As expected, we observed different movement planning biases across movement directions. The same pattern of biases was observed in a second experiment in which the starting position was translated 15 cm to the right of the participants’ midline. This indicates that the “straight ahead” direction, not one’s midline, serves as an important reference for movement planning during rotation adaptation.

Added value of money on motor performance feedback: Increased left central beta-band power for rewards and fronto-central theta-band power for punishments

&NA; Monetary rewards and punishments have been shown to respectively enhance retention of motor memories and short‐term motor performance, but their underlying neural bases in the context of motor control tasks remain unclear. Using electroencephalography (EEG), the present study tested the hypothesis that monetary rewards and punishments are respectively reflected in post‐feedback beta‐band (20–30 Hz) and theta‐band (3–8 Hz) oscillatory power. While participants performed upper limb reaching movements toward visual targets using their right hand, the delivery of monetary rewards and punishments was manipulated as well as their probability (i.e., by changing target size). Compared to unrewarded and unpunished trials, monetary rewards and the successful avoidance of punishments both entailed greater beta‐band power at left central electrodes overlaying contralateral motor areas. In contrast, monetary punishments and reward omissions both entailed increased theta‐band power at fronto‐central scalp sites. Additional analyses revealed that beta‐band power was further increased when rewards were lowly probable. In light of previous work demonstrating similar beta‐band modulations in basal ganglia during reward processing, the present results may reflect functional communication of reward‐related information between the basal ganglia and motor cortical regions. In turn, the increase in fronto‐central theta‐band power after monetary punishments may reflect an emphasized cognitive need for behavioral adjustments. Globally, the present work identifies possible neural substrates for the growing behavioral evidence showing beneficial effects of monetary feedback on motor learning and performance. HighlightsBeta‐ and theta‐band power encodes rewards and punishments in a motor task.Monetary feedback entails greater oscillatory power than performance feedback alone.Successful punishment avoidance entails similar beta‐band power as rewards.Beta‐band power is greater after lowly probable than highly probable target hits.Reward omissions entail similar fronto‐central theta‐band power as punishments.

Disruption of M1 Activity during Performance Plateau Impairs Consolidation of Motor Memories

Upon exposure to a new sensorimotor relationship, motor behaviors iteratively change early in adaptation but eventually stabilize as adaptation proceeds. Behavioral work suggests that motor memory consolidation is initiated upon the attainment of asymptotic levels of performance. Separate lines of evidence point to a critical role of the primary motor cortex (M1) in consolidation. However, a causal relationship between M1 activity during asymptote and consolidation has yet to be demonstrated. The present study investigated this issue in male and female participants using single-pulse transcranial magnetic stimulation (TMS) to interfere with postmovement activity in M1 in two behavioral phases of a ramp-and-hold visuomotor adaptation paradigm. TMS was either provided after each trial of the ramp phase of adaptation when a gradual increase in the visuomotor rotation caused movements to be changing, or after each trial of the hold phase of adaptation when the rotation was held constant and movements tended to stabilize. Consolidation was assessed by measuring performance on the same task 24 h later. Results revealed that TMS did not influence adaptation to the new visuomotor relationship in either condition. Critically, however, TMS disruption of M1 activity selectively impaired consolidation of motor memories when it was provided during the hold phase of adaptation. This effect did not take place when TMS was delivered over adjacent dorsal premotor cortex or when motor behaviors in late adaptation were prevented from plateauing. Together, these data suggest that the impaired consolidation stemmed from interference with mechanisms of repetition-dependent plasticity in M1. SIGNIFICANCE STATEMENT The present work demonstrates that TMS disruption of M1 activity impairs the consolidation of motor memories selectively when performance reaches asymptotic levels during sensorimotor adaptation. These findings provide evidence for a causal contribution of M1 to motor memory formation when movements tend to repeat, likely through mechanisms of repetition-dependent plasticity.

Serial practice impairs motor skill consolidation

Recent reports have revealed that motor skill learning is impaired if two skills are practiced one after the other, that is before the first skill has had the time to become consolidated. This suggests that motor skills should be practiced in isolation from one another to minimize interference. At the moment, little is known about the effect of practice schedules high in contextual interference on motor skill consolidation. In Experiment 1, we investigated whether a serial practice schedule impairs motor skill consolidation. Participants had to learn two distinct sequences of finger movements (A and B) under either a blocked practice schedule or a serial practice schedule before being retested the following day. A control group also practiced Sequence A only. Our results revealed that a blocked practice schedule led to no interference between the sequences, whereas a serial practice schedule impaired the consolidation of Sequence B. In Experiment 2, we investigated the origin of the interference caused by a serial practice schedule by replacing the physical practice of Sequence A with either the observation of a model performing Sequence A or by asking participants to produce random finger movements. Our results revealed that both tasks interfered with the consolidation of Sequence B. Thus, we suggest that a serial practice schedule impairs motor skill consolidation through a conflict in the brain networks involved in the acquisition of the cognitive representation of the sequence and its execution.