Department of Neurology, Emory University, Atlanta, Georgia.
Department of Psychology, Emory University, Atlanta, Georgia.
J Neurophysiol. 2020 Sep 1;124(3):728-739. doi: 10.1152/jn.00546.2019. Epub 2020 Jul 29.
In functional magnetic resonance imaging (fMRI) studies, performance of unilateral hand movements is associated with primary motor cortex activity ipsilateral to the moving hand (M1), in addition to contralateral activity (M1). The magnitude of M1 activity increases with the demand on precision of the task. However, it is unclear how demand-dependent increases in M1 recruitment relate to the control of hand movements. To address this question, we used fMRI to measure blood oxygenation level-dependent (BOLD) activity during performance of a task that varied in demand on precision. Participants ( = 23) manipulated an MRI-compatible joystick with their right or left hand to move a cursor into targets of different sizes (small, medium, large, extra large). Performance accuracy, movement time, and number of velocity peaks scaled with target size, whereas reaction time, maximum velocity, and initial direction error did not. In the univariate analysis, BOLD activation in M1 and M1 was higher for movements to smaller targets. Representational similarity analysis, corrected for mean activity differences, revealed multivoxel BOLD activity patterns during movements to small targets were most similar to those for medium targets and least similar to those for extra-large targets. Only models that varied with demand (target size, performance accuracy, and number of velocity peaks) correlated with the BOLD dissimilarity patterns, though differently for right and left hands. Across individuals, M1 and M1 similarity patterns correlated with each other. Together, these results suggest that increasing demand on precision in a unimanual motor task increases M1 activity and modulates M1 activity patterns. Contralateral primary motor cortex (M1) predominantly controls unilateral hand movements, but the role of ipsilateral M1 is unclear. We used functional magnetic resonance imaging (fMRI) to investigate how M1 activity is modulated by unimanual movements at different levels of demand on precision. Our results show that task characteristics related to demand on precision influence bilateral M1 activity, suggesting that in addition to contralateral M1, ipsilateral M1 plays a key role in controlling hand movements to meet performance precision requirements.
在功能磁共振成像（fMRI）研究中，单侧手部运动的表现与移动手对侧的初级运动皮层（M1）活动相关，此外还有对侧活动（M1）。M1 活动的幅度随着任务精度的要求而增加。然而，目前尚不清楚依赖任务的 M1 募集增加与手部运动控制之间的关系。为了解决这个问题，我们使用 fMRI 测量了在一项依赖精度要求的任务中血液氧合水平依赖（BOLD）活动。参与者（n=23）用右手或左手操纵一个与 MRI 兼容的操纵杆，将光标移动到不同大小的目标（小、中、大、特大）。表现精度、运动时间和速度峰值数量与目标大小相关，而反应时间、最大速度和初始方向误差则不相关。在单变量分析中，对于较小的目标，M1 和 M1 的 BOLD 激活更高。代表相似性分析，校正了平均活动差异，表明在较小目标运动期间的多体素 BOLD 活动模式与中等目标最相似，与特大目标最不相似。仅与需求（目标大小、表现精度和速度峰值数量）相关的模型与 BOLD 差异模式相关，但右手和左手的相关性不同。个体间，M1 和 M1 的相似性模式相互关联。总之，这些结果表明，在单臂运动任务中，对精度的要求增加会增加 M1 的活动并调节 M1 的活动模式。对侧初级运动皮层（M1）主要控制单侧手部运动，但对侧 M1 的作用尚不清楚。我们使用功能磁共振成像（fMRI）研究了在不同精度需求水平下，单侧运动如何调节 M1 活动。我们的结果表明，与精度需求相关的任务特征影响双侧 M1 活动，这表明除了对侧 M1 外，同侧 M1 在控制手部运动以满足性能精度要求方面也起着关键作用。
