Human premotor areas parse sequences into their spatial and temporal features.
Human premotor areas parse sequences into their spatial and temporal features.
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DOI：
10.7554/elife.03043
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发表时间：
2014-08-12
期刊：
影响因子：
7.7
通讯作者：
Diedrichsen J
中科院分区：
文献类型：
--
作者：
Kornysheva K;Diedrichsen J
熟练的表演的特点是在空间和时间上精确而灵活地控制动作序列。最近的理论表明，综合的时空轨迹是由运动和前运动网络的内在动力学产生的。这与当训练好的序列空间或时间特征被转移到一个新的时空组合时出现的行为优势形成对比，该组合主张这些序列特征的独立神经表征。我们使用了一种新的fMRI模式分类方法来识别具有独立表征和集成表征的大脑区域。在运动区域中发现了明显的区域分离：虽然只有对侧初级运动皮层对每个时空序列组合表现出独特的模式，但双侧运动前区相互独立地表现出空间和时间特征。这些发现表明，高级运动区域具有独特的功能，可以灵活地重组和有效地编码复杂的运动行为。DOI: http://dx.doi.org/10.7554/eLife.03043.001一旦钢琴家学会了演奏一首歌曲，他或她几乎可以毫不费力地重现演奏歌曲所需的手指动作序列，并带有特定的节奏。一个熟练的钢琴家也可以即兴演奏，用不同的节奏搭配相同的按键，或者用稍微不同的键序列演奏相同的节奏。这种在空间和时间上灵活调整和重组身体运动序列的能力，使人类在音乐、语言和许多其他需要运动技能的任务中表现出巨大的创造力。然而，允许这种灵活性的潜在大脑机制才刚刚开始被探索。一些科学家的理论认为，大脑中控制运动的部分的脑细胞网络将时间和空间序列作为一个不可分割的单元存储起来。然而，这一理论并不能解释为什么钢琴家和其他熟练的人能够以新的方式分离和重新组合一个序列的物理动作和时间。另一种观点是，大脑捕捉执行一系列物理动作所必需的信息，而不是这些动作将要执行的时间。这将允许这些功能以新的方式组合在一起。Kornysheva和Diedrichsen教了一组志愿者一系列配合特定节奏的手指动作。一半的志愿者用左手完成任务，另一半用右手。经过训练后，志愿者们在制作训练过的序列时表现得更好，即使在节奏或手指序列略有改变的试验中也是如此。志愿者还被要求完成训练后的动作，同时他们的大脑活动被功能性磁共振成形仪（fMRI）监测。Kornysheva和Diedrichsen寻找的是，每当执行特定的序列时，大脑活动增加和减少的模式相似的区域。该研究确定了在每个训练过的手指运动和节奏序列组合中显示出独特模式的区域，这可以与在节奏或手指运动中序列活动模式保持相似的区域区分开来。Kornysheva和Diedrichsen发现，大脑中控制运动的区域编码的序列与移动的手相反。在大脑的这个部分，运动和时间被编码为一个单元。然而，在运动前区域——已知是帮助个人计划运动的区域——时间和手指的运动似乎是在大脑两侧重叠的斑块中分别编码的。这种自动分离似乎是运动前皮层的一项基本功能，它使行为变得灵活，并在空间和时间上存储复杂的运动序列。DOI: http://dx.doi.org/10.7554/eLife.03043.002
Skilled performance is characterized by precise and flexible control of movement sequences in space and time. Recent theories suggest that integrated spatio-temporal trajectories are generated by intrinsic dynamics of motor and premotor networks. This contrasts with behavioural advantages that emerge when a trained spatial or temporal feature of sequences is transferred to a new spatio-temporal combination arguing for independent neural representations of these sequence features. We used a new fMRI pattern classification approach to identify brain regions with independent vs integrated representations. A distinct regional dissociation within motor areas was revealed: whereas only the contralateral primary motor cortex exhibited unique patterns for each spatio-temporal sequence combination, bilateral premotor areas represented spatial and temporal features independently of each other. These findings advocate a unique function of higher motor areas for flexible recombination and efficient encoding of complex motor behaviours. DOI: http://dx.doi.org/10.7554/eLife.03043.001 Once a pianist has learned to play a song, he or she can nearly effortlessly reproduce the sequence of finger movements needed to play the song with a particular rhythm. A skilled pianist can also improvise, pairing the same keystrokes with a different rhythm or playing the same rhythm with a slightly different sequence of keys. This ability to flexibly modify and recombine sequences of physical movements in space and time enables humans to exhibit great creativity in music, language, and many other tasks that require motor skills. However, the underlying brain mechanisms that allow this flexibility are only beginning to be explored. Some scientists have theorized that networks of brain cells in the parts of the brain that control movement store a sequence in time and space as one inseparable unit. However, this theory doesn't explain why pianists and other skilled individuals can separate and recombine the physical movements and timing of a sequence in new ways. An alternate idea is that the brain captures the information necessary to execute a series of physical movements separately from the timing at which the movements are to be carried out. This would allow these features to be put together in new ways. Kornysheva and Diedrichsen taught a group of volunteers a series of finger movements paired with particular rhythms. Half the volunteers performed the task using their left hand and the other half with their right hand. After training the volunteers performed better when producing sequences they had been trained on, even in trials where either the rhythm or the finger sequence was slightly changed. The volunteers were also asked to perform the trained movements while their brain activity was monitored in a functional magnetic resonance imaging (fMRI) machine. Kornysheva and Diedrichsen looked for areas that showed similar patterns of increases and decreases in activity whenever a particular sequence was performed. This identified areas that showed unique patterns for each trained sequence combination of finger movements and rhythm, which could be distinguished from areas where the activity patterns for sequences remained similar across rhythms or across finger movements. Kornysheva and Diedrichsen found that a region of the brain that controls movement encodes sequences on the opposite side of the brain from the moving hand. In this part of the brain, the movement and timing were encoded together as one unit. However, in premotor areas—which are known to help individuals to plan movements—the timing and the finger movements appeared to be encoded separately in overlapping patches on both sides of the brain. This automatic separation appears to be a fundamental function of the premotor cortex, enabling behavioural flexibility and the storage of complex sequences of movements in space and time. DOI: http://dx.doi.org/10.7554/eLife.03043.002