Hamel Raphaël, Trempe Maxime, Bernier Pierre-Michel
Département de kinanthropologie, Faculté des sciences de l'activité physique, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada, and.
Department of Sports Studies, Bishop's University, Sherbrooke, Québec J1M 1Z7, Canada.
J Neurosci. 2017 Sep 20;37(38):9197-9206. doi: 10.1523/JNEUROSCI.3916-16.2017. Epub 2017 Aug 18.
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. 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.
在接触新的感觉运动关系时，运动行为在适应早期会反复变化，但最终会随着适应过程的推进而稳定下来。行为学研究表明，运动记忆巩固在达到渐近性能水平时开始。多条证据表明初级运动皮层（M1）在巩固过程中起关键作用。然而，渐近期M1活动与巩固之间的因果关系尚未得到证实。本研究在男性和女性参与者中使用单脉冲经颅磁刺激（TMS）来干扰斜坡-保持视觉运动适应范式两个行为阶段中M1的运动后活动，以研究这个问题。TMS要么在适应斜坡阶段的每次试验后提供，此时视觉运动旋转逐渐增加导致运动发生变化，要么在适应保持阶段的每次试验后提供，此时旋转保持恒定且运动趋于稳定。通过测量24小时后在相同任务上的表现来评估巩固情况。结果显示，在两种情况下TMS均不影响对新视觉运动关系的适应。然而，至关重要的是，当在适应的保持阶段提供TMS时，对M1活动的TMS干扰选择性地损害了运动记忆的巩固。当TMS施加在相邻的背侧运动前皮层上或防止晚期适应中的运动行为达到平稳状态时，这种效应并未发生。总之，这些数据表明巩固受损源于对M1中重复依赖性可塑性机制的干扰。本研究表明，当感觉运动适应期间表现达到渐近水平时，TMS对M1活动的干扰选择性地损害运动记忆的巩固。这些发现为M1在运动倾向于重复时对运动记忆形成的因果贡献提供了证据，可能是通过重复依赖性可塑性机制。
