Cook N D
Department of Informatics, Kansai University, Takatsuki, Osaka 569-1089, Japan.
Neuroscience. 2008 May 15;153(3):556-70. doi: 10.1016/j.neuroscience.2008.02.042. Epub 2008 Feb 29.
An unusual property of the neuron is its capability for cell-to-cell communication via synapses, known to be the neuron-level "protophenomenon" underlying the brain-level "real phenomenon" of cognition. The temporal synchronization of such synaptic activity is the leading candidate for explaining "cognitive binding" and therefore the unity of mind. An equally-unusual property of the neuron is the action potential, the means by which the neuron sends a signal down the axon. Although infrequently noted by researchers in relation to consciousness, signal propagation within the neuron entails the momentary permeability of the neuronal membrane, allowing a massive influx of charged ions into the cellular interior. Such openness to the extracellular world is arguably the protophenomenon of neuronal "sentience," literally, feeling the charge-state of the electrochemical environment. Sensitivity to the external pH is a common feature of all living cells, but is greatly amplified during the neuron's action potential. Synchronization of the action potentials of the same neurons that are involved in cognitive binding is the likely mechanism by which the sentience of individual neurons is coordinated into the brain-level phenomenon of subjective awareness. I conclude that a proper understanding of the permeability of the neuronal membrane during the action potential is as important for consciousness studies as is a proper understanding of synaptic transmission for the explication of the cognition made possible by neurons.
神经元的一个不同寻常的特性是其通过突触进行细胞间通信的能力，而突触被认为是构成大脑层面认知“真实现象”基础的神经元层面的“原现象”。这种突触活动的时间同步性是解释“认知绑定”进而解释心智统一性的首要候选因素。神经元的另一个同样不同寻常的特性是动作电位，即神经元沿轴突发送信号的方式。尽管研究人员在讨论意识时很少提及，但神经元内的信号传播需要神经元膜瞬间通透，从而使大量带电离子涌入细胞内部。这种对细胞外环境的开放状态可以说是神经元“感知”的原现象，确切地说，就是感知电化学环境的电荷状态。对外部pH值敏感是所有活细胞的共同特征，但在神经元动作电位期间会大大增强。参与认知绑定的同一神经元动作电位的同步化，可能是将单个神经元的感知协调成大脑层面主观意识现象的机制。我的结论是，正确理解动作电位期间神经元膜的通透性对于意识研究的重要性，与正确理解突触传递对于解释神经元实现的认知的重要性相当。
