Pedrosa Victor, Clopath Claudia
Department of Bioengineering, Imperial College LondonLondon, UK; CAPES Foundation, Ministry of Education of BrazilBrasilia, Brazil.
Department of Bioengineering, Imperial College London London, UK.
Front Synaptic Neurosci. 2017 Jan 10;8:38. doi: 10.3389/fnsyn.2016.00038. eCollection 2016.
Neuromodulators play a ubiquitous role across the brain in regulating plasticity. With recent advances in experimental techniques, it is possible to study the effects of diverse neuromodulatory states in specific brain regions. Neuromodulators are thought to impact plasticity predominantly through two mechanisms: the gating of plasticity and the upregulation of neuronal activity. However, the consequences of these mechanisms are poorly understood and there is a need for both experimental and theoretical exploration. Here we illustrate how neuromodulatory state affects cortical plasticity through these two mechanisms. First, we explore the ability of neuromodulators to gate plasticity by reshaping the learning window for spike-timing-dependent plasticity. Using a simple computational model, we implement four different learning rules and demonstrate their effects on receptive field plasticity. We then compare the neuromodulatory effects of upregulating learning rate versus the effects of upregulating neuronal activity. We find that these seemingly similar mechanisms do not yield the same outcome: upregulating neuronal activity can lead to either a broadening or a sharpening of receptive field tuning, whereas upregulating learning rate only intensifies the sharpening of receptive field tuning. This simple model demonstrates the need for further exploration of the rich landscape of neuromodulator-mediated plasticity. Future experiments, coupled with biologically detailed computational models, will elucidate the diversity of mechanisms by which neuromodulatory state regulates cortical plasticity.
神经调质在整个大脑中对调节可塑性起着普遍作用。随着实验技术的最新进展，研究特定脑区中不同神经调节状态的影响成为可能。人们认为神经调质主要通过两种机制影响可塑性：可塑性的门控和神经元活动的上调。然而，这些机制的后果尚不清楚，需要进行实验和理论探索。在这里，我们阐述神经调节状态如何通过这两种机制影响皮质可塑性。首先，我们通过重塑依赖于尖峰时间的可塑性的学习窗口来探索神经调质对可塑性进行门控的能力。使用一个简单的计算模型，我们实现了四种不同的学习规则，并展示了它们对感受野可塑性的影响。然后，我们比较上调学习率的神经调节作用与上调神经元活动的作用。我们发现，这些看似相似的机制并不会产生相同的结果：上调神经元活动可能导致感受野调谐的拓宽或锐化，而上调学习率只会增强感受野调谐的锐化。这个简单的模型表明需要进一步探索神经调质介导的可塑性的丰富图景。未来的实验，结合具有生物学细节的计算模型，将阐明神经调节状态调节皮质可塑性的机制多样性。
