IEEE Trans Biomed Circuits Syst. 2020 Oct;14(5):1036-1050. doi: 10.1109/TBCAS.2020.3018777. Epub 2020 Aug 24.
Biological nonassociative learning is one of the simplest forms of unsupervised learning in animals and can be categorized into habituation and sensitization according to mechanism. This paper proposes a memristive circuit that is based on nonassociative learning and can adapt to repeated inputs, reduce power consumption (habituation), and be sensitive to harmful inputs (sensitization). The circuit includes 1) synapse module, 2) neuron module, 3) feedback module. The first module mainly consists of memristors representing synapse weights that vary with corresponding inputs. Memristance is automatically reduced when a harmful stimulus is input, and climbs at the input interval according to the feedback input when repeated stimuli are input. The second module produces spiking voltage when the total input is above the given threshold. The third module can provide feedback voltage according to the frequency and quantity of input stimuli. Simulation results show that the proposed circuit can generate output signals with biological nonassociative learning characteristics, with varying amplitudes depending on the characteristics of input signals. When the frequency and quantity of the input stimuli are high, the degree of habituation and sensitization intensifies. The proposed circuit has good robustness; can reduce the influence of noise, circuit parasitics and circuit aging during nonassociative learning; and simulate the afterimages caused by visual fatigue for application in automatic exposure compensation.
生物非联想学习是非监督学习在动物中的最简单形式之一，可以根据机制分为习惯化和敏感化。本文提出了一种基于非联想学习的忆阻电路，该电路可以适应重复输入，降低功耗（习惯化），并对有害输入敏感（敏感化）。该电路包括 1）突触模块，2）神经元模块，3）反馈模块。第一个模块主要由代表突触权重的忆阻器组成，这些权重随相应的输入而变化。当输入有害刺激时，忆阻器的电阻自动降低，而当重复输入刺激时，根据反馈输入在输入间隔上升。第二个模块在总输入超过给定阈值时产生尖峰电压。第三个模块可以根据输入刺激的频率和数量提供反馈电压。仿真结果表明，所提出的电路可以产生具有生物非联想学习特征的输出信号，其幅度随输入信号的特征而变化。当输入刺激的频率和数量较高时，习惯化和敏感化的程度会加剧。所提出的电路具有良好的鲁棒性；可以减少非联想学习过程中噪声、电路寄生和电路老化的影响；并模拟视觉疲劳引起的后像，用于自动曝光补偿的应用。
