Tal M
Brain Res. 1987 May 12;411(1):58-64. doi: 10.1016/0006-8993(87)90680-9.
The central pattern generator for rhythmic jaw movements is readily activated by repetitive stimulation (40 Hz) of the midbrain in the region of the cerebral peduncle in anaesthetized guinea pigs. The pattern of rhythmic digastric EMG evoked by midbrain stimulation after acute decerebration closely resembled that evoked by electrical stimulation of the masticatory cortex. Since the decerebration boundary was caudal to the substantia nigra and the thalamus, impulses ascending to these centers and others further rostral are not necessary for the generation of rhythmic jaw movements. This leaves local midbrain nuclei, and pathways descending from the forebrain (fibers-of-passage) as possible substrates for activating the rhythmic jaw movements. To distinguish between these two possibilities, midbrain stimulation was delivered in guinea pigs that underwent unilateral ablation of the masticatory cortex, and survived long enough to permit degeneration of all corticobulbar fibers that pass through the midbrain. In these animals no response was detected from stimulation of the ipsilateral midbrain. However, stimulation of the contralateral midbrain did evoke bilateral rhythmic digastric activity. These results suggest that rhythmic digastric activity and jaw movements evoked by midbrain stimulation are caused by activation of fibers that descend from the masticatory cortex, travel down through the midbrain, probably in the cerebral peduncle, and decussate only just rostral to the motor nucleus of the Vth cranial nerve.
在麻醉的豚鼠中，通过对大脑脚区域的中脑进行重复刺激（40赫兹），可轻易激活用于节律性颌部运动的中枢模式发生器。急性去大脑后，中脑刺激诱发的节律性二腹肌肌电图模式与咀嚼皮质电刺激诱发的模式极为相似。由于去大脑边界位于黑质和丘脑的尾侧，因此向这些中枢及更靠前脑区的冲动对于节律性颌部运动的产生并非必需。这使得局部中脑核团以及从前脑下行的通路（传导纤维）成为激活节律性颌部运动的可能底物。为区分这两种可能性，在单侧切除咀嚼皮质且存活时间足够长以允许所有穿过中脑的皮质延髓纤维发生变性的豚鼠中进行中脑刺激。在这些动物中，同侧中脑刺激未检测到反应。然而，对侧中脑刺激确实诱发了双侧节律性二腹肌活动。这些结果表明，中脑刺激诱发的节律性二腹肌活动和颌部运动是由从咀嚼皮质下行、穿过中脑（可能在大脑脚）且仅在第五对脑神经运动核前方交叉的纤维激活所致。
