Hoshino Osamu, Zheng Meihong, Watanabe Kazuo
Department of Intelligent Systems Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi, Ibaraki, 316-8511, Japan.
Southern Tohoku Research Institute for Neuroscience, Southern Tohoku General Hospital, 7-115, Yatsuyamada, Koriyama, Fukushima, 963-8563, Japan.
J Comput Neurosci. 2018 Apr;44(2):233-251. doi: 10.1007/s10827-018-0677-9. Epub 2018 Jan 31.
Recurrent input to sensory cortex, via long-range reciprocal projections between motor and sensory cortices, is essential for accurate perceptual judgments. GABA levels in sensory cortices correlate with perceptual performance. We simulated a neuron-astrocyte network model to investigate how top-down, feedback signaling from a motor network (Nmot) to a sensory network (Nsen) affects perceptual judgments in association with ambient (extracellular) GABA levels. In the Nsen, astrocytic transporters modulated ambient GABA levels around pyramidal cells. A simple perceptual task was implemented: detection of a feature stimulus presented to the Nsen. The Nmot showed distinct perceptual behaviors: hit, fault, and miss. A hit is a correct response to the stimulus, a fault is a wrong response to the stimulus, and a miss is no response to the stimulus. In hits, the feedback signaling increased the gain of Nsen pyramidal cells and accelerated the reaction speed of Nmot pyramidal cells to the stimulus. Without feedback signaling, the Nsen but not Nmot responded to the stimulus, resulting in a miss. With too strong feedback signaling, the Nmot resulted in a fault, namely, stimulus-insensitive but not stimulus-sensitive pyramidal cells wrongly responded. Balancing the feedforward and feedback signaling formed a coherent, ongoing-spontaneous neuronal state, by which the highest hit rate was achieved. A transient reduction in local ambient GABA levels, triggered by the stimulus, contributed to accelerating the reaction speed under noisy environmental conditions. Adjusting the basal ambient GABA level ensured high hit rates. We suggest that motor cortex feedback may accelerate reaction speed to sensory stimulation by promoting coherency in ongoing-spontaneous neuronal activity between sensory and motor cortices, thereby achieving prompt perceptual judgments. Spatiotemporal modulation of ambient GABA levels, possibly by astrocytic transporters, assists in making reliable perceptual judgments.
通过运动皮层和感觉皮层之间的长程相互投射，感觉皮层的反复输入对于准确的感知判断至关重要。感觉皮层中的GABA水平与感知表现相关。我们模拟了一个神经元-星形胶质细胞网络模型，以研究从运动网络（Nmot）到感觉网络（Nsen）的自上而下的反馈信号如何与周围（细胞外）GABA水平相关联地影响感知判断。在Nsen中，星形胶质细胞转运体调节锥体细胞周围的周围GABA水平。实施了一个简单的感知任务：检测呈现给Nsen的特征刺激。Nmot表现出不同的感知行为：命中、错误和未命中。命中是对刺激的正确反应，错误是对刺激的错误反应，未命中是对刺激无反应。在命中时，反馈信号增加了Nsen锥体细胞的增益，并加速了Nmot锥体细胞对刺激的反应速度。没有反馈信号时，Nsen而非Nmot对刺激做出反应，导致未命中。反馈信号过强时，Nmot会出现错误，即对刺激不敏感而非敏感的锥体细胞做出错误反应。平衡前馈和反馈信号形成了一种连贯的、持续自发的神经元状态，从而实现了最高的命中率。由刺激引发的局部周围GABA水平的短暂降低，有助于在嘈杂的环境条件下加速反应速度。调整基础周围GABA水平可确保高命中率。我们认为，运动皮层反馈可能通过促进感觉皮层和运动皮层之间持续自发神经元活动的连贯性来加速对感觉刺激的反应速度，从而实现迅速的感知判断。周围GABA水平的时空调节，可能是通过星形胶质细胞转运体，有助于做出可靠的感知判断。
