Department of Morphological Brain Science, Graduate School of Medicine, Kyoto University, Kyoto, 606-8501, Japan.
Laboratory for Behavioral Neurophysiology, Brain Science Institute, RIKEN, Wako, Saitama, 351-0198, Japan.
Brain Struct Funct. 2018 Mar;223(2):851-872. doi: 10.1007/s00429-017-1522-z. Epub 2017 Oct 9.
Massive corticothalamic afferents originating from layer 6a of primary sensory cortical areas modulate sensory responsiveness of thalamocortical neurons and are pivotal for shifting neuronal firing between burst and tonic modes. The influence of the corticothalamic pathways on the firing mode and sensory gain of thalamic neurons has only been extensively examined in anesthetized animals, but has yet to be established in the awake state. We made lesions of the rat barrel cortex and on the following day recorded responses of single thalamocortical and thalamic reticular neurons to a single vibrissal deflection in the somatosensory system during wakefulness. Our results showed that the cortical lesions shifted the response of thalamic neurons towards bursting, elevated the response probability and the gain of thalamocortical neurons, predominantly of recurring responses. In addition, after the lesions, the spontaneous activities of the vibrissa-responsive thalamic neurons, but not those of vibrissa-unresponsive cells, were typified by waxing-and-waning spindle-like rhythmic spiking with frequent bursting. In awake rats with intact cortex, identified layer 6a corticothalamic neurons responded to a single vibrissal deflection with short latencies that matched those of layer 4 neurons, strongly suggesting the existence of an immediate corticothalamic feedback. The present results show the importance of corticothalamic neurons in shaping thalamic activities during wakefulness.
大量源自初级感觉皮层 6a 层的皮质丘脑传入纤维调节丘脑皮层神经元的感觉反应，对于在爆发和紧张模式之间切换神经元放电至关重要。皮质丘脑通路对丘脑神经元的放电模式和感觉增益的影响仅在麻醉动物中得到广泛研究，但在清醒状态下尚未建立。我们对大鼠的桶状皮层进行了损伤，第二天在清醒状态下记录了单个丘脑皮层和丘脑网状神经元对单个触须偏转的反应。我们的结果表明，皮层损伤使丘脑神经元的反应向爆发转变，提高了丘脑皮层神经元的反应概率和增益，主要是反复出现的反应。此外，损伤后，触须反应性丘脑神经元的自发活动，而不是触须非反应性细胞的自发活动，以逐渐增强和减弱的纺锤状节律性刺发放电为特征，频繁爆发。在皮层完整的清醒大鼠中，鉴定出的 6a 层皮质丘脑神经元对单个触须偏转的反应具有与 4 层神经元相匹配的短潜伏期，强烈表明存在即时的皮质丘脑反馈。本研究结果表明，皮质丘脑神经元在清醒状态下塑造丘脑活动方面具有重要作用。
