Identification of neuronal ensembles mediating fear generalization in the infralimbic cortex

项目摘要 创伤后应激障碍（PTSD）困扰着8%的美国人口。PTSD的一个突出症状是 创伤记忆的过度概括泛化是指学习的迁移， 类似的刺激，但不完全相同，以原来的条件刺激（CS）。尽管重要的是 在基本记忆处理和创伤后应激障碍中，对一般化的理解， 神经元基质记忆被认为是编码在稀疏的，分布的神经元群中， “神经元集合体”随着时间的推移，支持记忆表达的神经元集合是动态的。 泛化也是动态的，随着时间的推移有增加的趋势，这表明 两个.神经科学中的一个主要问题是整体动力学如何介导 随着时间的推移，边缘下皮层（infarimbic cortex，IL）是大脑中对泛化有贡献的一个区域。 尽管IL在泛化中的作用是已知的，但IL神经元集合体介导的识别仍然是未知的。 随时间的泛化过程是未知的。研究神经元集合的一个障碍是 在整体识别和操作中固有的技术困难。新的分子工具，如 ArcCreERT 2 x EYFP转基因小鼠，用于在培养期间永久“标记”活性细胞（Arc/arg3.1表达）， 与记忆回忆过程中活跃的细胞进行比较，已经推进了这一领域。在目标1中，我们使用 ArcCreERT 2 x EYFP小鼠在学习期间标记IL中的细胞，以与回忆期间激活的细胞进行比较 无论是CS或后一个新的音调（泛化或歧视）在最近或远程保留间隔。 虽然“标记”技术提供了一个进入神经元系综动力学的窗口，但神经元系综动力学的分辨率仍然很低。 方法有限。提供更高的时间分辨率（亚秒级）以识别神经元集合 动力学，我们将在体内钙离子成像可视化，测量和比较协调的IL合奏 随着时间的推移与恐惧泛化相关的活动。在目标2中，全球IL活性和恐惧之间的因果关系 将建立使用化学遗传学双向调节IL锥体神经元的一般化 激发活性依赖性（ArcCreERT 2）化学遗传学将用于测试合成的 重新激活其活动先前与泛化相关联的少量神经元（即，一 “泛化集成”）足以驱动泛化表达。我很好地勾勒了一个研究计划- 适合本科神经科学研究。几乎所有提出的技术都已经被 在我的实验室里成功地完成了。预计这些实验产生的数据不仅 加强瓦萨大学的本科生研究，但将导致对恐惧泛化的更好理解 在神经元集合水平上的过程，希望为PTSD的治疗策略提供信息。

PROJECT SUMMARY Posttraumatic stress disorder (PTSD) afflicts 8% of the US population. One prominent symptom of PTSD is the over-generalization of traumatic memories. Generalization refers to the transfer of learned responding to stimuli that are similar, but not identical, to the original conditioned stimulus (CS). Despite the importance of understanding generalization, in both basic memory processing and PTSD, very little is known about the neuronal substrates. Memory is thought to be encoded in sparse, distributed groups of neurons known as “neuronal ensembles.” Over time, neuronal ensembles supporting memory expression are dynamic. Generalization is also dynamic, with a tendency to increase over time, suggesting a relationship between the two. A major question in neuroscience is how ensemble dynamics mediate changes in the expression of generalization over time. One brain region shown to contribute to generalization is the infralimbic cortex (IL). Despite a known role for the IL in generalization, the identification of IL neuronal ensembles mediating generalization processes over time is unknown. One obstacle in the way of studying neuronal ensembles is the inherent technical difficulty in ensemble identification and manipulation. New molecular tools, such as ArcCreERT2 x EYFP transgenic mice, for permanently “tagging” active cells (Arc/arg3.1 expression) during learning for comparison with cells active during memory recall, has advanced the field. In Aim 1, we use ArcCreERT2 x EYFP mice to tag cells in the IL during learning for comparison with cells activated during recall of either the CS or after a novel tone (generalization or discrimination) at recent or remote retention intervals. While “tagging” technology provides a window into neuronal ensemble dynamics, the resolution of the approach is limited. To provide greater temporal resolution (subsecond) for identifying neuronal ensembles dynamics, we incorporate in vivo Ca2+ imaging to visualize, measure, and compare coordinated IL ensemble activity associated with fear generalization over time. In Aim 2, a causal link between global IL activity and fear generalization will be established using chemogenetics to bi-directional modulate IL pyramidal neuron excitation. Activity-dependent (ArcCreERT2) chemogenetics will be used to test whether the synthetic reactivation of a small number of neurons whose activity was previously associated with generalization (i.e., a ”generalization ensemble”) is sufficient to drive generalization expression. I have outlined a research plan well- suited for undergraduate neuroscience research. Nearly all proposed techniques have already been successfully carried out in my lab. It is anticipated the data generated by these experiments will not only strengthen undergraduate research at Vassar but will lead to a greater understanding of fear generalization processes at the level of neuronal ensembles, with the hope of informing treatment strategies for PTSD.