Department of Neurobiology and Anatomy, Drexel University College of Medicine, 2900 Queen Lane, Philadelphia, PA 19129, USA.
J Neurophysiol. 2010 Mar;103(3):1147-57. doi: 10.1152/jn.00955.2009. Epub 2010 Jan 6.
Neocortex network activity varies from a desynchronized or activated state typical of arousal to a synchronized or deactivated state typical of quiescence. Such changes are usually attributed to the effects of neuromodulators released in the neocortex by nonspecific activating systems originating in basal forebrain and brain stem reticular formation. As a result, the only role attributed to thalamocortical cells projecting to primary sensory areas, such as barrel cortex, is to transmit sensory information. However, thalamocortical cells can undergo significant changes in spontaneous tonic firing as a function of state, although the role of such variations is unknown. Here we show that the tonic firing level of thalamocortical cells, produced by cholinergic and noradrenergic stimulation of the somatosensory thalamus in urethane-anesthetized rats, controls neocortex activation and deactivation. Thus in addition to its well-known role in the relay of sensory information, the thalamus can control the state of neocortex activation, which may complement the established roles in this regard of basal forebrain and brain stem nuclei. Because of the topographical organization of primary thalamocortical pathways, this mechanism provides a means by which area-specific neocortical activation can occur, which may be useful for modality-specific sensory processing or selective attention.
新皮层网络活动的变化范围从觉醒时的去同步或激活状态到安静时的同步或去激活状态。这种变化通常归因于非特异性激活系统在基底前脑和脑干网状结构中释放的神经调质对新皮层的影响。因此，投射到初级感觉区域（如桶状皮层）的丘脑皮质细胞的唯一作用被认为是传递感觉信息。然而，丘脑皮质细胞的自发紧张放电可以根据状态发生显著变化，尽管这种变化的作用尚不清楚。在这里，我们表明，在乌拉坦麻醉大鼠的体感丘脑中，乙酰胆碱能和去甲肾上腺素能刺激产生的丘脑皮质细胞的紧张放电水平控制着新皮层的激活和失活。因此，除了在感觉信息传递中的已知作用外，丘脑还可以控制新皮层激活的状态，这可能补充了基底前脑和脑干核在这方面的既定作用。由于初级丘脑皮质通路的拓扑组织，这种机制提供了一种方法，可以实现特定区域的新皮层激活，这对于特定感觉处理或选择性注意可能是有用的。
