Coenen A M
Department of Psychology, University of Nijmegen, The Netherlands.
Conscious Cogn. 1998 Mar;7(1):42-53. doi: 10.1006/ccog.1997.0324.
The neuroanatomical substrates controlling and regulating sleeping and waking, and thus consciousness, are located in the brain stem. Most crucial for bringing the brain into a state conducive for consciousness and information processing is the mesencephalic part of the brain stem. This part controls the state of waking, which is generally associated with a high degree of consciousness. Wakefulness is accompanied by a low-amplitude, high-frequency electroencephalogram, due to the fact that thalamocortical neurons fire in a state of tonic depolarization. Information can easily pass the low-level threshold of these neurons, leading to a high transfer ratio. The complexity of the electroencephalogram during conscious waking is high, as expressed in a high correlation dimension. Accordingly, the level of information processing is high. Spindles, and alpha waves in humans, mark the transition from wakefulness to sleep. These phenomena are related to drowsiness, associated with a reduction in consciousness. Drowsiness occurs when cells undergo moderate hyperpolarizations. Increased inhibitions result in a reduction of afferent information, with a lowered transfer ratio. Information processing subsides, which is also expressed in a diminished correlation dimension. Consciousness is further decreased at the onset of slow wave sleep. This sleep is controlled by the medullar reticular formation and is characterized by a high-voltage, low-frequency electroencephalogram. Slow wave sleep becomes manifest when neurons undergo a further hyperpolarization. Inhibitory activities are so strong that the transfer ratio further drops, as does the correlation dimension. Thus, sensory information is largely blocked and information processing is on a low level. Finally, rapid eye movement sleep is regulated by the pontine reticular formation and is associated with a "wake-like" electroencephalographic pattern. Just as during wakefulness, this is the expression of a depolarization of thalamocortical neurons. The transfer ratio of rapid eye movement sleep has not yet been determined, but seems to vary. Evidence exists that this type of sleep, associated with dreaming, with some kind of perception and consciousness, is involved in processing of "internal" information. In line with this, rapid eye movement sleep has higher correlation dimensions than slow-wave sleep and sometimes even higher than wakefulness. It is assumed that the "near-the-threshold" depolarized state of neurons in the thalamus and cerebral cortex is a necessary condition for perceptual processes and consciousness, such as occurs during waking and in an altered form during rapid eye movement sleep.
控制和调节睡眠与觉醒，进而调节意识的神经解剖学基质位于脑干。脑干中脑部分对于使大脑进入有利于意识和信息处理的状态最为关键。这部分控制觉醒状态，觉醒通常与高度的意识相关。觉醒时伴随着低振幅、高频脑电图，这是因为丘脑皮质神经元在紧张性去极化状态下放电。信息能够轻易越过这些神经元的低水平阈值，从而导致高传递率。清醒时脑电图的复杂性很高，表现为高关联维数。相应地，信息处理水平也很高。纺锤波以及人类的阿尔法波标志着从觉醒到睡眠的转变。这些现象与嗜睡有关，嗜睡伴随着意识的降低。当细胞经历中度超极化时就会出现嗜睡。抑制作用增强导致传入信息减少，传递率降低。信息处理减弱，这也表现为关联维数减小。在慢波睡眠开始时意识进一步下降。这种睡眠由延髓网状结构控制，其特征是高电压、低频率脑电图。当神经元进一步超极化时慢波睡眠就会显现。抑制活动非常强烈，传递率和关联维数进一步下降。因此，感觉信息在很大程度上被阻断，信息处理处于低水平。最后，快速眼动睡眠由脑桥网状结构调节，并且与“类似觉醒”的脑电图模式相关。就像在觉醒期间一样，这是丘脑皮质神经元去极化的表现。快速眼动睡眠的传递率尚未确定，但似乎有所不同。有证据表明，这种与做梦、某种感知和意识相关的睡眠类型参与“内部”信息的处理。与此一致的是，快速眼动睡眠的关联维数高于慢波睡眠，有时甚至高于觉醒状态。据推测，丘脑和大脑皮质中神经元的“接近阈值”去极化状态是感知过程和意识的必要条件，比如在觉醒期间以及在快速眼动睡眠期间以改变的形式出现时。
