The brain matters: effects of descending signals on motor control.
The brain matters: effects of descending signals on motor control.
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大脑很重要：下降信号对运动控制的影响。
DOI：
10.1152/jn.00107.2012
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发表时间：
2012
影响因子：
2.5
通讯作者：
Friesen,WOtto
中科院分区：
文献类型：
--
作者：
Mullins,OliviaJ;Friesen,WOtto
在许多物种中，神经索和脊髓在没有大脑的情况下表现出虚构的节律性运动的能力已得到充分证明。尽管大脑对于调节虚构的运动输出很重要，但人们普遍认为，在简化的制剂中识别出的神经元回路的功能特性在连接大脑的情况下是保守的。我们通过检查最近在水蛭（Hirudo verbana）神经索中发现的新型中间神经元的特性来检验这一假设。这个神经元，细胞E21，在被剥夺头脑的分离水蛭神经索的准备过程中启动并驱动刻板的虚构游泳活动。我们报告说，与预期相反，在附有大脑的制剂中刺激细胞 E21 时产生的运动输出是高度可变的。其中一些准备中游泳频率和发作持续时间增加，而另一些准备中游泳频率和持续时间减少。细胞 E21 部分地通过与细胞 204 的兴奋性突触相互作用来控制游泳，细胞 204 先前确定了门控神经元，当大脑缺席时，门控神经元可靠地启动并强烈增强水蛭的游泳活动。我们发现，在有大脑存在的制剂中，从细胞 E21 到细胞 204 的突触相互作用的强度降低了 50%，并且细胞 204 诱发的反应也高度可变。有趣的是，大多数这种变异性在半完整制剂中消失了。我们得出的结论是，在减少的制剂中发现的神经元回路特性可能会从根本上改变在更多生理条件下发生的神经元回路特性。
The ability of nerve cords and spinal cords to exhibit fictive rhythmic locomotion in the absence of the brain is well-documented in numerous species. Although the brain is important for modulating the fictive motor output, it is broadly assumed that the functional properties of neuronal circuits identified in simplified preparations are conserved with the brain attached. We tested this assumption by examining the properties of a novel interneuron recently identified in the leech (Hirudo verbana) nerve cord. This neuron, cell E21, initiates and drives stereotyped fictive swimming activity in preparations of the isolated leech nerve cord deprived of the head brain. We report that, contrary to expectation, the motor output generated when cell E21 is stimulated in preparations with the brain attached is highly variable. Swim frequency and episode duration are increased in some of these preparations and decreased in others. Cell E21 controls swimming, in part, via excitatory synaptic interactions with cells 204, previously identified gating neurons that reliably initiate and strongly enhance leech swimming activity when the brain is absent. We found that in preparations with the brain present, the magnitude of the synaptic interaction from cell E21 to cell 204 is reduced by 50% and that cell 204-evoked responses also were highly variable. Intriguingly, most of this variability disappeared in semi-intact preparations. We conclude that neuronal circuit properties identified in reduced preparations might be fundamentally altered from those that occur in more physiological conditions.