Kwag Jeehyun, Jang Hyun Jae, Kim Mincheol, Lee Sujeong
Neural Computation Laboratory, Department of Brain and Cognitive Engineering, Korea University, Seoul, Korea
Neural Computation Laboratory, Department of Brain and Cognitive Engineering, Korea University, Seoul, Korea.
J R Soc Interface. 2014 Oct 6;11(99). doi: 10.1098/rsif.2014.0604.
Rate and phase codes are believed to be important in neural information processing. Hippocampal place cells provide a good example where both coding schemes coexist during spatial information processing. Spike rate increases in the place field, whereas spike phase precesses relative to the ongoing theta oscillation. However, what intrinsic mechanism allows for a single neuron to generate spike output patterns that contain both neural codes is unknown. Using dynamic clamp, we simulate an in vivo-like subthreshold dynamics of place cells to in vitro CA1 pyramidal neurons to establish an in vitro model of spike phase precession. Using this in vitro model, we show that membrane potential oscillation (MPO) dynamics is important in the emergence of spike phase codes: blocking the slowly activating, non-inactivating K+ current (IM), which is known to control subthreshold MPO, disrupts MPO and abolishes spike phase precession. We verify the importance of adaptive IM in the generation of phase codes using both an adaptive integrate-and-fire and a Hodgkin-Huxley (HH) neuron model. Especially, using the HH model, we further show that it is the perisomatically located IM with slow activation kinetics that is crucial for the generation of phase codes. These results suggest an important functional role of IM in single neuron computation, where IM serves as an intrinsic mechanism allowing for dual rate and phase coding in single neurons.
速率编码和相位编码被认为在神经信息处理中很重要。海马位置细胞就是一个很好的例子，在空间信息处理过程中，这两种编码方式共存。在位置域中，动作电位发放速率增加，而动作电位相位相对于正在进行的θ振荡呈进动状态。然而，单个神经元产生包含这两种神经编码的动作电位输出模式的内在机制尚不清楚。我们使用动态钳制技术，将位置细胞类似体内的阈下动力学模拟到体外培养的CA1锥体神经元上，以建立动作电位相位进动的体外模型。利用这个体外模型，我们发现膜电位振荡（MPO）动力学在动作电位相位编码的出现中很重要：阻断已知可控制阈下MPO的缓慢激活、非失活钾电流（IM），会破坏MPO并消除动作电位相位进动。我们使用自适应积分发放模型和霍奇金-赫胥黎（HH）神经元模型，验证了适应性IM在相位编码产生中的重要性。特别是，使用HH模型，我们进一步表明，对于相位编码的产生至关重要的是位于胞体周围、具有缓慢激活动力学的IM。这些结果表明IM在单个神经元计算中具有重要的功能作用，其中IM作为一种内在机制，允许单个神经元进行双重速率和相位编码。
