Department of Otolaryngology, Eye and Ear Institute, University of Pittsburgh, Room 519, Pittsburgh, PA 15213, USA.
Exp Brain Res. 2013 Mar;225(3):349-59. doi: 10.1007/s00221-012-3376-1. Epub 2012 Dec 29.
The dorsolateral reticular formation of the caudal medulla, the lateral tegmental field (LTF), participates in generating vomiting. LTF neurons exhibited complex responses to vestibular stimulation in decerebrate cats, indicating that they received converging inputs from a variety of labyrinthine receptors. Such a convergence pattern of vestibular inputs is appropriate for a brain region that participates in generating motion sickness. Since responses of brainstem neurons to vestibular stimulation can differ between decerebrate and conscious animals, the current study examined the effects of whole-body rotations in vertical planes on the activity of LTF neurons in conscious felines. Wobble stimuli, fixed-amplitude tilts, the direction of which moves around the animal at a constant speed, were used to determine the response vector orientation, and also to ascertain whether neurons had spatial-temporal convergence (STC) behavior (which is due to the convergence of vestibular inputs with different spatial and temporal properties). The proportion of LTF neurons with STC behavior in conscious animals (25 %) was similar to that in decerebrate cats. Far fewer neurons in other regions of the feline brainstem had STC behavior, confirming findings that many LTF neurons receive converging inputs from a variety of labyrinthine receptors. However, responses to vertical plane vestibular stimulation were considerably different in decerebrate and conscious felines for LTF neurons lacking STC behavior. In decerebrate cats, most LTF neurons had graviceptive responses to rotations, similar to those of otolith organ afferents. However, in conscious animals, the response properties were similar to those of semicircular canal afferents. These differences show that higher centers of the brain that are removed during decerebration regulate the labyrinthine inputs relayed to the LTF, either by gating connections in the brainstem or by conveying vestibular inputs directly to the region.
延髓尾侧背外侧网状结构，即外侧被盖区（LTF），参与呕吐的产生。LTF 神经元在去大脑猫中对前庭刺激表现出复杂的反应，表明它们接收来自各种迷路感受器的会聚输入。这种前庭输入的会聚模式适合于参与晕动病产生的脑区。由于脑干神经元对前庭刺激的反应在去大脑和有意识动物之间可能不同，因此目前的研究检查了在垂直平面内全身旋转对有意识猫 LTF 神经元活性的影响。摆动刺激，固定幅度倾斜，其方向以恒定速度围绕动物移动，用于确定响应向量方向，并且还确定神经元是否具有时空会聚（STC）行为（这是由于具有不同空间和时间特性的前庭输入的会聚引起的）。在有意识动物中具有 STC 行为的 LTF 神经元的比例（25％）与去大脑猫中的比例相似。在猫脑干的其他区域中，具有 STC 行为的神经元要少得多，这证实了许多 LTF 神经元接收来自各种迷路感受器的会聚输入的发现。然而，对于缺乏 STC 行为的 LTF 神经元，垂直平面前庭刺激的反应在去大脑和有意识猫中差异很大。在去大脑猫中，大多数 LTF 神经元对旋转具有重感反应，类似于耳石器官传入的反应。然而，在有意识的动物中，反应特性类似于半规管传入的反应。这些差异表明，在去大脑过程中被切除的大脑更高中心调节传递到 LTF 的迷路输入，要么通过在脑干中门控连接，要么通过将前庭输入直接传递到该区域。
