Department of Physiology, University of Bern, Bühlplatz 5, CH-3012 Bern, Switzerland.
Proc Natl Acad Sci U S A. 2009 Dec 1;106(48):20482-6. doi: 10.1073/pnas.0910379106. Epub 2009 Nov 16.
Almost nothing is known about dendritic activity in awake animals and even less about its relationship to behavior. The tuft dendrites of layer 5 (L5) pyramidal neurons lie in layer 1, where long-range axons from secondary thalamic nuclei and higher cortical areas arrive. This class of input is very dependent on active thalamo-cortical loops and activity in higher brain areas and so is likely to be heavily influenced by the conscious state of the animal. If, as has been suggested, the dendrites of pyramidal neurons actively participate in this process, dendritic activity should greatly increase in the awake state. Here, we measured calcium activity in L5 pyramidal neuron dendrites using the "periscope" fiberoptic system. Recordings were made in the sensorimotor cortex of awake and anesthetized rats following sensory stimulation of the hindlimb. Bi-phasic dendritic responses evoked by hindlimb stimulation were extremely dependent on brain state. In the awake state, there was a prominent slow, delayed response whose integral was on average 14-fold larger than in the anesthetized state. Moreover, the dramatic increases in dendritic activity closely correlated to the strength of subsequent hindlimb movement. These changes were confined to L5 pyramidal dendrites and were not reflected in the response of layer 2/3 (L2/3) neurons to air-puff stimuli in general (which actually decreased in the awake state). The results demonstrate that the activity of L5 pyramidal dendrites is a neural correlate of awake behavior.
在清醒动物中，树突活动几乎一无所知，更不用说其与行为的关系了。第 5 层（L5）锥体神经元的树突位于第 1 层，长程轴突来自次级丘脑核和更高的皮质区。这一类输入非常依赖于活跃的丘脑皮质环路和大脑更高区域的活动，因此很可能受到动物清醒状态的强烈影响。如果如前所述，锥体神经元的树突积极参与这个过程，那么在清醒状态下，树突活动应该会大大增加。在这里，我们使用“潜望镜”光纤系统测量 L5 锥体神经元树突中的钙活动。在感觉刺激后，在清醒和麻醉大鼠的感觉运动皮层中进行了记录。后腿刺激引起的双相树突反应极其依赖于大脑状态。在清醒状态下，有一个明显的缓慢、延迟反应，其积分平均比麻醉状态下大 14 倍。此外，树突活动的剧烈增加与随后后腿运动的强度密切相关。这些变化仅限于 L5 锥体树突，而一般不会反映在空气喷刺激下 L2/3（L2/3）神经元的反应中（实际上在清醒状态下会减少）。结果表明，L5 锥体树突的活动是清醒行为的神经相关物。
