Department of Physiology, Technion-Israel Institute of Technology, Haifa, Israel.
Department of Neurobiology, University of Haifa, Haifa, Israel.
Elife. 2021 Oct 26;10:e70383. doi: 10.7554/eLife.70383.
The piriform cortex (PCx) is essential for learning of odor information. The current view postulates that odor learning in the PCx is mainly due to plasticity in intracortical (IC) synapses, while odor information from the olfactory bulb carried via the lateral olfactory tract (LOT) is 'hardwired.' Here, we revisit this notion by studying location- and pathway-dependent plasticity rules. We find that in contrast to the prevailing view, synaptic and optogenetically activated LOT synapses undergo strong and robust long-term potentiation (LTP) mediated by only a few local NMDA-spikes delivered at theta frequency, while global spike timing-dependent plasticity (STDP) protocols failed to induce LTP in these distal synapses. In contrast, IC synapses in apical and basal dendrites undergo plasticity with both NMDA-spikes and STDP protocols but to a smaller extent compared with LOT synapses. These results are consistent with a self-potentiating mechanism of odor information via NMDA-spikes that can form branch-specific memory traces of odors that can further associate with contextual IC information via STDP mechanisms to provide cognitive and emotional value to odors.
梨状皮层(PCx)对于学习气味信息至关重要。目前的观点假设,PCx 中的气味学习主要归因于皮质内(IC)突触的可塑性,而来自嗅球的气味信息通过外侧嗅束(LOT)“硬连线”传递。在这里,我们通过研究位置和途径依赖性的可塑性规则来重新审视这个概念。我们发现,与流行的观点相反,突触和光遗传学激活的 LOT 突触通过仅在 theta 频率下传递几个局部 NMDA 尖峰,经历强烈和稳健的长时程增强(LTP),而全局尖峰时间依赖性可塑性(STDP)方案未能在这些远端突触中诱导 LTP。相比之下,在顶端和基底树突中的 IC 突触通过 NMDA 尖峰和 STDP 方案进行可塑性,但与 LOT 突触相比,程度较小。这些结果与 NMDA 尖峰通过自我增强机制形成气味的分支特异性记忆痕迹一致,该机制可以通过 STDP 机制与 IC 信息进一步关联,为气味提供认知和情感价值。