Phillips W A, Larkum M E, Harley C W, Silverstein S M
School of Natural Sciences, University of Stirling, Scotland FK9 4LA, UK.
Neurocure Cluster of Excellence, Department of Biology, Humboldt University, Charitéplatz 1, Berlin 10117, Germany.
Neurosci Conscious. 2016 Sep 11;2016(1):niw015. doi: 10.1093/nc/niw015. eCollection 2016.
Neocortical pyramidal cells can integrate two classes of input separately and use one to modulate response to the other. Their tuft dendrites are electrotonically separated from basal dendrites and soma by the apical dendrite, and apical hyperpolarization-activated currents (I) further isolate subthreshold integration of tuft inputs. When apical depolarization exceeds a threshold, however, it can enhance response to the basal inputs that specify the cell's selective sensitivity. This process is referred to as apical amplification (AA). We review evidence suggesting that, by regulating I in the apical compartments, adrenergic arousal controls the coupling between apical and somatic integration zones thus modifying cognitive capabilities closely associated with consciousness. Evidence relating AA to schizophrenia, sleep, and anesthesia is reviewed, and we assess theories that emphasize the relevance of AA to consciousness. Implications for theories of neocortical computation that emphasize context-sensitive modulation are summarized. We conclude that the findings concerning AA and its regulation by arousal offer a new perspective on states of consciousness, the function and evolution of neocortex, and psychopathology. Many issues worthy of closer examination arise.
新皮层锥体细胞可以分别整合两类输入，并利用其中一类来调节对另一类的反应。它们的簇状树突通过顶端树突与基底树突和胞体在电紧张上分离，并且顶端超极化激活电流（Ih）进一步隔离了簇状输入的阈下整合。然而，当顶端去极化超过阈值时，它可以增强对指定细胞选择性敏感性的基底输入的反应。这个过程被称为顶端放大（AA）。我们回顾了相关证据，表明通过调节顶端区室中的Ih，肾上腺素能觉醒控制顶端和体细胞整合区之间的耦合，从而改变与意识密切相关的认知能力。我们还回顾了将AA与精神分裂症、睡眠和麻醉相关的证据，并评估了强调AA与意识相关性的理论。总结了对强调上下文敏感调制的新皮层计算理论的影响。我们得出结论，关于AA及其由觉醒调节机制的研究结果为意识状态、新皮层的功能和进化以及精神病理学提供了一个新的视角。许多值得更深入研究的问题由此产生。
