Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, ON M5G1X5, Canada.
Neuron. 2011 Nov 17;72(4):572-86. doi: 10.1016/j.neuron.2011.09.005.
A neural network can sustain and switch between different activity patterns to execute multiple behaviors. By monitoring the decision making for directional locomotion through motor circuit calcium imaging in behaving Caenorhabditis elegans (C. elegans), we reveal that C. elegans determines the directionality of movements by establishing an imbalanced output between the forward and backward motor circuits and that it alters directions by switching between these imbalanced states. We further demonstrate that premotor interneurons modulate endogenous motoneuron activity to establish the output imbalance. Specifically, the UNC-7 and UNC-9 innexin-dependent premotor interneuron-motoneuron coupling prevents a balanced output state that leads to movements without directionality. Moreover, they act as shunts to decrease the backward-circuit activity, establishing a persistent bias for the high forward-circuit output state that results in the inherent preference of C. elegans for forward locomotion. This study demonstrates that imbalanced motoneuron activity underlies directional movement and establishes gap junctions as critical modulators of the properties and outputs of neural circuits.
神经网络可以维持和切换不同的活动模式，以执行多种行为。通过监测行为秀丽隐杆线虫（C. elegans）中运动回路钙成像的定向运动决策，我们揭示线虫通过在前后运动回路之间建立不平衡的输出来确定运动的方向性，并且通过在这些不平衡状态之间切换来改变方向。我们进一步证明，前运动神经元调节内源性运动神经元活动以建立输出不平衡。具体来说，UNC-7 和 UNC-9 缝隙连接依赖性前运动神经元-运动神经元偶联防止导致无方向性运动的平衡输出状态。此外，它们充当分流器以降低后回路活动，为高前回路输出状态建立持久的偏差，导致线虫对向前运动的固有偏好。这项研究表明，不平衡的运动神经元活动是定向运动的基础，并确立了缝隙连接作为神经回路特性和输出的关键调节剂。
