The Largest Response Component in the Motor Cortex Reflects Movement Timing but Not Movement Type.
The Largest Response Component in the Motor Cortex Reflects Movement Timing but Not Movement Type.
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DOI：
10.1523/eneuro.0085-16.2016
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发表时间：
2016-07
期刊：
影响因子：
3.4
通讯作者：
Churchland MM
中科院分区：
文献类型：
--
作者：
Kaufman MT;Seely JS;Sussillo D;Ryu SI;Shenoy KV;Churchland MM
猴子运动皮质(M1)和背侧运动前皮质(PMD)的神经活动可以在运动开始之前很好地反映所选择的运动。就在运动开始之前，神经活动的模式发生了深刻的变化。我们认为，从准备到运动的转变可能伴随着神经状态的巨大整体变化，这反映了什么时候进行运动，而不是什么运动。这一预测源于形式上的考虑。具体地说，我们研究了群体反应的“组成部分”：每个神经元的反应大致由其组成的活动的时变模式。在单个M1和PMD神经元的反应复杂性中，我们识别出“条件不变”的强健反应成分：它们的大小和时间进程几乎相同，无论到达的方向或路径如何。这些条件不变的反应成分占据了与“调谐”反应成分所占据的维度垂直的维度。最大的条件不变成分比任何调谐成分都大得多，也就是说，它更好地解释了单个神经元反应的结构。这种条件不变的反应成分在运动开始前经历了快速变化。这一变化的时机预测了反应时间的大部分逐个试验的差异。因此，尽管单个M1和PMD神经元基本上总是反映做出了哪种运动，但群体反应的最大组成部分反映的是运动时间而不是运动类型。
Neural activity in monkey motor cortex (M1) and dorsal premotor cortex (PMd) can reflect a chosen movement well before that movement begins. The pattern of neural activity then changes profoundly just before movement onset. We considered the prediction, derived from formal considerations, that the transition from preparation to movement might be accompanied by a large overall change in the neural state that reflects when movement is made rather than which movement is made. Specifically, we examined “components” of the population response: time-varying patterns of activity from which each neuron’s response is approximately composed. Amid the response complexity of individual M1 and PMd neurons, we identified robust response components that were “condition-invariant”: their magnitude and time course were nearly identical regardless of reach direction or path. These condition-invariant response components occupied dimensions orthogonal to those occupied by the “tuned” response components. The largest condition-invariant component was much larger than any of the tuned components; i.e., it explained more of the structure in individual-neuron responses. This condition-invariant response component underwent a rapid change before movement onset. The timing of that change predicted most of the trial-by-trial variance in reaction time. Thus, although individual M1 and PMd neurons essentially always reflected which movement was made, the largest component of the population response reflected movement timing rather than movement type.