Penhune V B, Doyon J
Department of Psychology, Concordia University, SP-A 244, 7141 Sherbrooke St. W, Montreal, Canada QC H4B 1R6.
Neuroimage. 2005 Jul 1;26(3):801-12. doi: 10.1016/j.neuroimage.2005.02.041. Epub 2005 Apr 7.
We used positron emission tomography (PET) to examine within-day learning of timed motor sequences. The results of this experiment are novel in showing an interaction between cerebellum and primary motor cortex (M1) during learning that appears to be mediated by the dentate nucleus (DN) and in demonstrating that activity in these regions is directly related to performance. Subjects were scanned during learning (LRN) across three blocks of practice and during isochronous (ISO) and perceptual (PER) baseline conditions. CBF was compared across blocks of learning and between the LRN and baseline conditions. Results demonstrated an interaction between the cerebellum and M1 such that earlier, poorer performance was associated with greater activity in the cerebellar hemispheres and later, better performance was associated with greater activity in M1. Inter-regional correlation analyses confirmed that as CBF in the cerebellum decreases, blood flow in M1 increases. Importantly, these analyses also revealed that activity in cerebellar cortex was positively correlated with activity in right DN and that DN activity was negatively correlated with blood flow in M1. Activity in the cerebellar hemispheres early in learning is likely related to error correction mechanisms which optimize movement kinematics resulting in improved performance. Concurrent DN activity may be related to encoding of this information and DN output to M1 may play a role in consolidation processes that lay down motor memories. Increased activity in M1 later in learning may reflect strengthening of synaptic connections associated with changes in motor maps that are characteristic of learning in both animals and humans.
我们使用正电子发射断层扫描（PET）来检测定时运动序列的日内学习情况。本实验结果具有创新性，表明学习过程中小脑与初级运动皮层（M1）之间存在一种相互作用，这种相互作用似乎由齿状核（DN）介导，并且证明这些区域的活动与表现直接相关。在学习过程中（LRN），对受试者进行了三个练习块的扫描，并在等时（ISO）和感知（PER）基线条件下进行了扫描。比较了各学习块之间以及LRN与基线条件之间的脑血流量（CBF）。结果表明小脑与M1之间存在相互作用，即早期表现较差与小脑半球的活动增加有关，而后期表现较好与M1的活动增加有关。区域间相关性分析证实，随着小脑CBF的减少，M1的血流量增加。重要的是，这些分析还表明，小脑皮层的活动与右侧DN的活动呈正相关，而DN的活动与M1的血流量呈负相关。学习早期小脑半球的活动可能与错误纠正机制有关，该机制优化运动运动学，从而提高表现。同时发生的DN活动可能与该信息的编码有关，并且DN向M1的输出可能在形成运动记忆的巩固过程中发挥作用。学习后期M1活动的增加可能反映了与运动图谱变化相关的突触连接的加强，这是动物和人类学习的特征。
