Escudero M, Vidal P P
Laboratorio de Neurociencia, Facultad de Biología, Universidad de Sevilla, Spain.
Eur J Neurosci. 1996 Mar;8(3):572-80. doi: 10.1111/j.1460-9568.1996.tb01242.x.
The qualitative and quantitative characteristics of cerebral cortex electrical activity, ocular motility and muscular activity were studied in six head-restrained guinea-pigs during wakefulness, slow-wave and paradoxical sleep. Animals were chronically implanted with bipolar electrodes in the obliquus capitis muscle for electromyographic recordings and epidurally through the parietal bones for electroencephalographic (EEG) recordings. Eye movements were recorded using the scleral search-coil technique. After postoperative recovery and a short period of habituation to immobilization, head-restrained animals exhibited a polyphasic sleep-wake cycle similar to what has already been described in the unrestrained guinea-pig. Paradoxical sleep periods of mean duration 110 +/- 42 s occurred at a mean interval of 32.2 +/- 7.2 min. Amplitude and frequency components of EEG activity were different for each state of vigilance. EEG amplitude was highest and frequency range lowest-with two well-defined peaks at 4 and 10 Hz-during slow-wave sleep. During paradoxical sleep, frequencies were higher and amplitudes lower than during wakefulness. Three types of eye movement intermingled with periods of ocular fixation were recorded: saccadic movements during wakefulness and paradoxical sleep, slow drifts during slow-wave sleep and paradoxical sleep, and a new type of eye movement-bursts of high-velocity eye oscillations during paradoxical sleep. Saccadic eye movements during paradoxical sleep were more frequent and showed higher velocities and amplitudes than during wakefulness. During paradoxical sleep the episodes of eye oscillation (8-14 Hz) occurred quite regularly every 1.6 s and had a mean duration of 1.4 s. During wakefulness, the obliquus muscle activity displayed a burst-tonic pattern. Bursting components were closely related to saccadic eye movements directed to the side of the recorded muscle. The muscle activity was predominantly tonic during slow-wave sleep and was completely absent during paradoxical sleep except for small bursts or twitches. These twitches were tightly synchronized with the occurrence of the rapid eye movements oriented towards the side of the recorded obliquus muscle, as during wakefulness. These results strongly suggest that paradoxical sleep is characterized by the oscillatory discharge of at least two neuronal populations: the brainstem saccadic generators and the tecto-reticular spinal network which underlies gaze-orienting behaviour during wakefulness. The occurrence of rhythmic discharges at approximately 11 Hz may explain the spinal motoneurons' inhibition during paradoxical sleep in order to avoid anarchic motor behavior. Whether these neuronal oscillations are simply an epiphenomenon or have functional implications remains to be determined.
在六只头部受限的豚鼠清醒、慢波睡眠和异相睡眠期间，研究了大脑皮质电活动、眼球运动和肌肉活动的定性和定量特征。动物被长期植入电极，在头斜肌中植入双极电极用于肌电图记录，通过顶骨硬膜外植入电极用于脑电图（EEG）记录。使用巩膜搜索线圈技术记录眼球运动。术后恢复并经过短时间适应固定后，头部受限的动物表现出多相睡眠-觉醒周期，类似于在未受限豚鼠中已经描述的情况。平均持续时间为110±42秒的异相睡眠期平均间隔为32.2±7.2分钟。脑电图活动的振幅和频率成分在每种警觉状态下都不同。在慢波睡眠期间，脑电图振幅最高，频率范围最低，有两个明确的峰值，分别在4赫兹和10赫兹。在异相睡眠期间，频率高于清醒时，振幅低于清醒时。记录到三种类型的眼球运动与眼球固定期交织在一起：清醒和异相睡眠期间的快速眼球运动、慢波睡眠和异相睡眠期间的缓慢漂移，以及一种新型的眼球运动——异相睡眠期间的高速眼球振荡爆发。异相睡眠期间的快速眼球运动比清醒时更频繁，速度和振幅更高。在异相睡眠期间，眼球振荡（8 - 14赫兹）的发作相当规律，每隔1.6秒出现一次，平均持续时间为1.4秒。在清醒期间，头斜肌活动呈现爆发-紧张模式。爆发成分与指向记录肌肉一侧的快速眼球运动密切相关。在慢波睡眠期间，肌肉活动主要是紧张性的，在异相睡眠期间除了小的爆发或抽搐外完全没有活动。这些抽搐与朝向记录的头斜肌一侧的快速眼球运动的出现紧密同步，如同在清醒时一样。这些结果强烈表明，异相睡眠的特征是至少两个神经元群体的振荡放电：脑干快速眼球运动发生器和在清醒期间构成注视定向行为基础的顶盖-网状脊髓网络。大约11赫兹的节律性放电的出现可能解释了异相睡眠期间脊髓运动神经元的抑制，以避免无规律的运动行为。这些神经元振荡仅仅是一种附带现象还是具有功能意义仍有待确定。
