Laboratory of Synaptic Mechanisms, Brain Mind Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Neuroscientist. 2024 Feb;30(1):87-104. doi: 10.1177/10738584221108083. Epub 2022 Jul 13.
Unraveling the neuronal mechanisms of fear learning might allow neuroscientists to make links between a learned behavior and the underlying plasticity at specific synaptic connections. In fear learning, an innocuous sensory event such as a tone (called the conditioned stimulus, CS) acquires an emotional value when paired with an aversive outcome (unconditioned stimulus, US). Here, we review earlier studies that have shown that synaptic plasticity at thalamic and cortical afferents to the lateral amygdala (LA) is critical for the formation of auditory-cued fear memories. Despite the early progress, it has remained unclear whether there are separate synaptic inputs that carry US information to the LA to act as a teaching signal for plasticity at CS-coding synapses. Recent findings have begun to fill this gap by showing, first, that thalamic and cortical auditory afferents can also carry US information; second, that the release of neuromodulators contributes to US-driven teaching signals; and third, that synaptic plasticity additionally happens at connections up- and downstream of the LA. Together, a picture emerges in which coordinated synaptic plasticity in serial and parallel circuits enables the formation of a finely regulated fear memory.
解析恐惧学习的神经元机制可能使神经科学家能够在特定的突触连接之间建立习得行为与潜在可塑性之间的联系。在恐惧学习中，无害的感觉事件（如音调）（称为条件刺激，CS）与厌恶的结果（非条件刺激，US）配对时会获得情感价值。在这里，我们回顾了早期的研究，这些研究表明，外侧杏仁核（LA）的丘脑和皮质传入的突触可塑性对于听觉提示恐惧记忆的形成至关重要。尽管取得了早期进展，但仍不清楚是否存在单独的突触输入，将 US 信息传递到 LA 作为 CS 编码突触可塑性的教学信号。最近的发现开始填补这一空白，首先表明，丘脑和皮质听觉传入也可以携带 US 信息；其次，神经调质的释放有助于 US 驱动的教学信号；第三，LA 上下游的连接也会发生突触可塑性。总的来说，一幅画面出现了，在这个画面中，串联和并联电路中的协调突触可塑性使精细调节的恐惧记忆得以形成。
