Modulation of circuit feedback specifies motor circuit output.
Modulation of circuit feedback specifies motor circuit output.
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DOI：
10.1523/jneurosci.1461-12.2012
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发表时间：
2012-07-04
期刊：
影响因子：
--
通讯作者：
Nusbaum MP
中科院分区：
文献类型：
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作者：
Blitz DM;Nusbaum MP
功能水平之间的双向通信（即前馈和反馈途径）在神经系统中很常见，但在大多数系统中，关于反馈途径的功能和可修改性知之甚少。我们正在探索这个问题在螃蟹（巨蟹座）口胃神经系统通过检查投射神经元和他们的目标中央模式发生器（CPG）电路神经元之间的双向通信。具体来说，我们解决了这样的问题：肽能POC神经元是否仅通过激活投射神经元或通过另外改变CPG反馈到这些投射神经元的强度来触发口胃神经节中的特定胃磨（咀嚼）运动模式。POC触发的胃磨节律是由CPG神经元对投射神经元的反馈抑制形成的。在这里，我们建立了POC刺激触发反馈介导的IPSC/Ps在投射神经元，持续相同的持续时间作为POC胃磨节奏的持久增强。这种增强的CPG反馈似乎是突触前调制的结果，因为它也发生在其他投射神经元中，这些投射神经元的活性在POC刺激后不会改变。为了确定这种强化的反馈突触的功能，我们比较了POC刺激后，将POC前和POC后幅度的动态钳位注入反馈IPSP到关键投射神经元的影响。只有后POC振幅IPSPs引起的POC触发的活动模式，在这个投射神经元，使充分表达的POC胃磨节律。因此，CPG反馈到投射神经元的强度是可修改的，并且可以有助于运动模式选择。
Bidirectional communication (i.e. feedforward and feedback pathways) between functional levels is common in neural systems, but in most systems little is known regarding the function and modifiability of the feedback pathway. We are exploring this issue in the crab (Cancer borealis) stomatogastric nervous system by examining bidirectional communication between projection neurons and their target central pattern generator (CPG) circuit neurons. Specifically, we addressed the question of whether the peptidergic POC neurons trigger a specific gastric mill (chewing) motor pattern in the stomatogastric ganglion solely by activating projection neurons, or by additionally altering the strength of CPG feedback to these projection neurons. The POC-triggered gastric mill rhythm is shaped by feedback inhibition onto projection neurons from a CPG neuron. Here we establish that POC stimulation triggers a long-lasting enhancement of feedback-mediated IPSC/Ps in the projection neurons, which persists for the same duration as POC-gastric mill rhythms. This strengthened CPG feedback appears to result from presynaptic modulation, because it also occurs in other projection neurons whose activity does not change after POC stimulation. To determine the function of this strengthened feedback synapse, we compared the influence of dynamic clamp-injected feedback IPSPs of pre- and post-POC amplitude into a pivotal projection neuron after POC stimulation. Only the post-POC amplitude IPSPs elicited the POC-triggered activity pattern in this projection neuron and enabled full expression of the POC-gastric mill rhythm. Thus, the strength of CPG feedback to projection neurons is modifiable and can be instrumental to motor pattern selection.