近日，nature杂志在线发表了瑞士和法国研究人员的研究成果。虽然人们普遍认为基于任务或经验的学习涉及特定神经回路内的变化，但我们才刚刚开始了解这些变化是怎样发生的以及这些回路内不同类型神经元之间的哪些相互作用是重要的。
研究人员以小鼠经典的、基于音调的恐惧条件反射作为一个模型体系，识别出一个截然不同的、基于“去抑制”的回路，它对于学习至关重要。
研究人员提供的证据表明，这个回路并不是听觉皮层特有的，而是可能代表着“胆碱能神经调制”门控皮层活动的一个普遍机制。（生物谷Bioon.com）
doi:10.1038/nature10674
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A disinhibitory microcircuit for associative fear learning in the auditory cortex
Johannes J. Letzkus, Steffen B. E. Wolff, Elisabeth M. M. Meyer, Philip Tovote, Julien Courtin, Cyril Herry & Andreas Lüthi
Learning causes a change in how information is processed by neuronal circuits. Whereas synaptic plasticity, an important cellular mechanism, has been studied in great detail, we know much less about how learning is implemented at the level of neuronal circuits and, in particular, how interactions between distinct types of neurons within local networks contribute to the process of learning. Here we show that acquisition of associative fear memories depends on the recruitment of a disinhibitory microcircuit in the mouse auditory cortex. Fear-conditioning-associated disinhibition in auditory cortex is driven by foot-shock-mediated cholinergic activation of layer 1 interneurons, in turn generating inhibition of layer 2/3 parvalbumin-positive interneurons. Importantly, pharmacological or optogenetic block of pyramidal neuron disinhibition abolishes fear learning. Together, these data demonstrate that stimulus convergence in the auditory cortex is necessary for associative fear learning to complex tones, define the circuit elements mediating this convergence and suggest that layer-1-mediated disinhibition is an important mechanism underlying learning and information processing in neocortical circuits.
