FUNCTIONAL ORGANIZATION OF CERVICAL SPINAL INTERNEURONS

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。在本报告所述期间，继续对颈脊髓神经元的特性进行研究。这些研究将阐明脊髓回路对正常行为灵长类动物自主运动控制的贡献。我们的长期目标是了解和克服与CNS损伤或疾病相关的运动缺陷。 到目前为止，C3-C4神经元的活动已记录在3个清醒的，行为猕猴训练，使手腕，达到，等长的头部运动。大多数神经元的活动在手臂的行为调制没有响应，在孤立的头部运动。肌电活动（EMG）的尖峰触发平均值（STA）确定了与肌肉的功能联系。在316个神经元中，27%的神经元在STA中表现出明显的特征。大多数（64%）的影响跨越或之前的尖峰放电时间，其发病lavelets过早引起的神经元运动神经元的突触连接。大多数与尖峰相关的影响发生在肩部和手臂肌肉。平滑的神经元放电率和EMG之间的交叉相关记录了每个任务的活动的协变。61%的测试神经元与EMG具有显著的峰值相关性，颈部，肩部和手臂肌肉的比例相似。我们的数据支持C3-C4神经元在手臂运动过程中招募任务依赖性肌肉协同作用的作用。这些细胞也可能在手臂运动期间帮助协调颈部和手臂肌肉的活动。 在C6-T1节段的神经元的定向调谐确定多维手腕运动之前和之后的离子电渗应用GABA能和甘氨酸能拮抗剂。阻断抑制对大多数神经元的定向调谐影响不大。这表明抑制调节脊髓神经元的兴奋性和增益控制，而不是塑造方向性调谐。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. During the period covered by this report, studies continued on the properties of neurons in the cervical spinal cord. These studies will elucidate the contribution of spinal cord circuits to the control of voluntary movements in normal, behaving primates. Our long-term goal is understand, and overcome, the motor deficits associated with CNS injury or disease. To date, the activity of C3-C4 neurons has been recorded in 3 awake, behaving macaques trained to make wrist, reaching, and isometric head movements. Most neurons whose activity was modulated during the arm behaviors did not respond during isolated head movements. Spike-triggered averages (STAs) of electromyographic activity (EMG) identified functional linkages with muscles. 27% of 316 neurons exhibited significant features in STAs. The majority (64%) of effects straddled or preceded the spike discharge time; their onset latencies were too early to be caused by synaptic connections of the neuron to motoneurons. Most of the spike-related effects were in shoulder and arm muscles. Cross-correlations between smoothed neuronal firing rate and EMG documented the covariation of activity for each task. 61% of the tested neurons had significant peak correlations with EMG, with similar proportions for neck, shoulder, and arm muscles. Our data support a role for C3-C4 neurons in recruiting task-dependent muscle synergies during arm movements. It is also possible that these cells help coordinate the activity of neck and arm muscles during arm movements. The directional tuning of neurons in the C6-T1 segments was determined for multi-dimensional wrist movements before and after the iontophoretic application of GABAergic and glycinergic antagonists. Block of inhibition had little effect on the neurons' directional tuning for the majority of neurons. This suggests that inhibition regulates spinal neuron excitability and gain control, rather than shaping directional tuning.