Department of Neuroscience, City University of Hong Kong, Hong Kong, China.
Centre for Regenerative Medicine and Health, Hong Kong Institute of Science & Innovation, Chinese Academy of Sciences, Hong Kong, China.
Elife. 2024 Mar 4;13:e83356. doi: 10.7554/eLife.83356.
The entorhinal cortex is involved in establishing enduring visuo-auditory associative memory in the neocortex. Here we explored the mechanisms underlying this synaptic plasticity related to projections from the visual and entorhinal cortices to the auditory cortex in mice using optogenetics of dual pathways. High-frequency laser stimulation (HFS laser) of the visuo-auditory projection did not induce long-term potentiation. However, after pairing with sound stimulus, the visuo-auditory inputs were potentiated following either infusion of cholecystokinin (CCK) or HFS laser of the entorhino-auditory CCK-expressing projection. Combining retrograde tracing and RNAscope in situ hybridization, we show that expression is higher in entorhinal cortex neurons projecting to the auditory cortex than in those originating from the visual cortex. In the presence of CCK, potentiation in the neocortex occurred when the presynaptic input arrived 200 ms before postsynaptic firing, even after just five trials of pairing. Behaviorally, inactivation of the CCK projection from the entorhinal cortex to the auditory cortex blocked the formation of visuo-auditory associative memory. Our results indicate that neocortical visuo-auditory association is formed through heterosynaptic plasticity, which depends on release of CCK in the neocortex mostly from entorhinal afferents.
内嗅皮层参与在新皮层中建立持久的视听联想记忆。在这里，我们使用双通路光遗传学方法探索了与视觉和内嗅皮层投射到听觉皮层相关的突触可塑性的机制。视觉-听觉投射的高频激光刺激（HFS 激光）不会诱导长时程增强。然而，在与声音刺激配对后，在给予胆囊收缩素（CCK）或 HFS 激光刺激内嗅-听觉 CCK 表达投射后，视觉-听觉输入被增强。通过逆行追踪和 RNAscope 原位杂交，我们表明，投射到听觉皮层的内嗅皮层神经元的表达高于起源于视觉皮层的神经元。在 CCK 的存在下，当突触前输入在突触后放电前 200 毫秒到达时，即使在仅仅五次配对试验后，新皮层中的增强仍然发生。行为上，内嗅皮层到听觉皮层的 CCK 投射的失活阻断了视觉-听觉联想记忆的形成。我们的结果表明，新皮层的视听联想是通过异突触可塑性形成的，这主要依赖于内嗅传入释放 CCK。
