Burst and tonic response modes in thalamic neurons during sleep and wakefulness.
Burst and tonic response modes in thalamic neurons during sleep and wakefulness.
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DOI：
10.1152/jn.2001.85.3.1107
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发表时间：
2001-03
影响因子：
2.5
通讯作者：
T. Weyand;Michael Boudreaux;W. Guido
中科院分区：
文献类型：
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作者：
T. Weyand;Michael Boudreaux;W. Guido
丘脑神经元可以表现出两种不同的放电模式：强直和爆发。在外侧膝状核（LGN）中，强直模式表现为视觉信息从视网膜到皮层的相对忠实的中继。对突发模式的功能了解较少。它在慢波睡眠（SWS）中普遍存在，并与同步皮质脑电图（EEG）相关联，表明它在慢波睡眠中起重要作用。虽然不常见，但在清醒时也会发生爆裂。本研究的目的是确定影响突发概率的条件，并比较睡眠和清醒时的突发发生率。LGN神经元在睡眠和清醒时爆发的程度是非常不同的。一些LGN神经元在任何清醒状态下都不会爆发，一些在慢波睡眠状态下也不会爆发。在清醒状态下，<1%的动作电位与脑破裂有关，而在睡眠状态下，这一比例跃升至18%。虽然在慢波睡眠期间爆发最为常见，但超过50%的爆发源于14%的LGN细胞。睡眠时爆发主要局限于持续1-5秒的发作，其中约47%的发作是有节奏的，在δ频率范围内（0.5- 4hz）。在清醒状态下，尽管视觉刺激导致了最多的脉冲，但它仍然只占总反应的一小部分（4%，93个细胞中742个脉冲/17,744个周期）。我们确定了影响突发概率的两个变量：用于引发反应的视觉刺激的大小和行为状态。增加刺激规模增加爆发概率。我们将此归因于大刺激对细胞抑制机制的影响增加。就像睡眠一样，大部分的爆裂都是由少数细胞引起的。在视觉刺激时，9%的神经元产生50%的破裂。警惕性增强与突发概率负相关。在主动注视期间呈现的视觉刺激（即，当动物必须注视一个明显的注视点时）比在没有注视点的情况下呈现相同的视觉刺激（“被动”注视）时更不容易产生爆裂。这些观察结果表明，即使短暂地离开专注状态，也会使神经元过度极化，足以使爆发机制失效。我们的结果为慢波睡眠中爆发的时间结构提供了新的视角；在完整的动物中支持幕式节律性活动的器官。此外，由于爆发可能与清醒状态下的特定条件有关，我们认为爆发在这种状态下具有特定的功能。
Thalamic neurons can exhibit two distinct firing modes: tonic and burst. In the lateral geniculate nucleus (LGN), the tonic mode appears as a relatively faithful relay of visual information from retina to cortex. The function of the burst mode is less understood. Its prevalence during slow-wave sleep (SWS) and linkage to synchronous cortical electroencephalogram (EEG) suggest that it has an important role during this form of sleep. Although not nearly as common, bursting can also occur during wakefulness. The goal of this study was to identify conditions that affect burst probability, and to compare burst incidence during sleeping and waking. LGN neurons are extraordinarily heterogenous in the degree to which they burst, during both sleeping and waking. Some LGN neurons never burst under any conditions during wakefulness, and several never burst during slow-wave sleep. During wakefulness, <1% of action potentials were associated with bursting, whereas during sleep this fraction jumps to 18%. Although bursting was most common during slow-wave sleep, more than 50% of the bursting originated from 14% of the LGN cells. Bursting during sleep was largely restricted to episodes lasting 1-5 s, with approximately 47% of these episodes being rhythmic and in the delta frequency range (0.5-4 Hz). In wakefulness, although visual stimulation accounted for the greatest number of bursts, it was still a small fraction of the total response (4%, 742 bursts/17,744 cycles in 93 cells). We identified two variables that appeared to influence burst probability: size of the visual stimuli used to elicit responses and behavioral state. Increased stimulus size increased burst probability. We attribute this to the increased influence large stimuli have on a cell's inhibitory mechanisms. As with sleep, a large fraction of bursting originated from a small number of cells. During visual stimulation, 50% of bursting was generated by 9% of neurons. Increased vigilance was negatively correlated with burst probability. Visual stimuli presented during active fixation (i.e., when the animal must fixate on an overt fixation point) were less likely to produce bursting, than when the same visual stimuli were presented but no fixation point present ("passive" fixation). Such observations suggest that even brief departures from attentive states can hyperpolarize neurons sufficiently to de-inactivate the burst mechanism. Our results provide a new view of the temporal structure of bursting during slow-wave sleep; one that supports episodic rhythmic activity in the intact animal. In addition, because bursting could be tied to specific conditions within wakefulness, we suggest that bursting has a specific function within that state.