Mameli O, Melis F
Institute of Human Physiology, University of Sassari, Italy.
Brain Res Bull. 1992 Feb;28(2):239-44. doi: 10.1016/0361-9230(92)90185-z.
The experiments were designed to show whether visual inputs and somatosensory signals travelling along the common radial nerves converge onto the same hypoglossal neurons. The hypoglossal neurons (HN) type I (45.77%) and II (33.89%) responded to both visual and somatosensory stimuli. The HN type III (15.26%) responded only to the retinae and type IV (5.08%) only to the forelimb nerves stimulation. In the convergent neurons, types I and II, the influence of the somatosensory stimulation on the hypoglossal visual response was also analyzed. The conditioning stimulation of the radial nerve significantly increased (31%) the hypoglossal response to the less effective retina and significantly reduced (17%) the response to the more effective retina. The recordings of the electromyographic activity of the genioglossus (GM) and the superior longitudinal muscle (SLM), showed that the somatosensory afferents synergize the excitatory effect of the visual messages on the extrinsic tongue muscles (GM) and antagonize the inhibitory effect that visual messages induce on the intrinsic tongue muscles (SLM). The results suggest that visual messages induce tongue reflex responses functionally directed not only to prepare the oral cavity better for food reception, as previously demonstrated, but also to modulate the postural tone of the tongue together with somatosensory signals.
这些实验旨在表明，沿共同的桡神经传播的视觉输入和躯体感觉信号是否会汇聚到同一舌下神经元上。I型（45.77%）和II型（33.89%）舌下神经元对视觉和躯体感觉刺激均有反应。III型舌下神经元（15.26%）仅对视网膜有反应，IV型（5.08%）仅对前肢神经刺激有反应。在I型和II型汇聚神经元中，还分析了躯体感觉刺激对舌下视觉反应的影响。桡神经的条件刺激显著增加了（31%）舌下神经对效果较差的视网膜的反应，并显著降低了（17%）对效果较好的视网膜的反应。颏舌肌（GM）和舌上纵肌（SLM）的肌电图活动记录表明，躯体感觉传入神经协同视觉信息对外侧舌肌（GM）的兴奋作用，并拮抗视觉信息对舌内肌（SLM）诱导的抑制作用。结果表明，视觉信息不仅如先前所示能诱导舌反射反应，在功能上使口腔更好地准备接受食物，还能与躯体感觉信号一起调节舌的姿势张力。
