Human Informatics and Interaction Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8566, Japan; Neural Computation Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan.
Health and Medical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8564, Japan; Animal Resources Section, Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan.
Neuroimage. 2024 Oct 1;299:120840. doi: 10.1016/j.neuroimage.2024.120840. Epub 2024 Sep 5.
Previous studies of operant learning have addressed neuronal activities and network changes in specific brain areas, such as the striatum, sensorimotor cortex, prefrontal/orbitofrontal cortices, and hippocampus. However, how changes in the whole-brain network are caused by cellular-level changes remains unclear. We, therefore, combined resting-state functional magnetic resonance imaging (rsfMRI) and whole-brain immunohistochemical analysis of early growth response 1 (EGR1), a marker of neural plasticity, to elucidate the temporal and spatial changes in functional networks and underlying cellular processes during operant learning. We used an 11.7-Tesla MRI scanner and whole-brain immunohistochemical analysis of EGR1 in mice during the early and late stages of operant learning. In the operant training, mice received a reward when they pressed left and right buttons alternately, and were punished with a bright light when they made a mistake. A group of mice (n = 22) underwent the first rsfMRI acquisition before behavioral sessions, the second acquisition after 3 training-session-days (early stage), and the third after 21 training-session-days (late stage). Another group of mice (n = 40) was subjected to histological analysis 15 min after the early or late stages of behavioral sessions. Functional connectivity increased between the limbic areas and thalamus or auditory cortex after the early stage of training, and between the motor cortex, sensory cortex, and striatum after the late stage of training. The density of EGR1-immunopositive cells in the motor and sensory cortices increased in both the early and late stages of training, whereas the density in the amygdala increased only in the early stage of training. The subcortical networks centered around the limbic areas that emerged in the early stage have been implicated in rewards, pleasures, and fears. The connectivities between the motor cortex, somatosensory cortex, and striatum that consolidated in the late stage have been implicated in motor learning. Our multimodal longitudinal study successfully revealed temporal shifts in brain regions involved in behavioral learning together with the underlying cellular-level plasticity between these regions. Our study represents a first step towards establishing a new experimental paradigm that combines rsfMRI and immunohistochemistry to link macroscopic and microscopic mechanisms involved in learning.
先前的操作性学习研究主要集中在特定脑区的神经元活动和网络变化，如纹状体、感觉运动皮层、前额叶/眶额皮层和海马体。然而，细胞水平的变化如何导致全脑网络的变化尚不清楚。因此，我们结合静息态功能磁共振成像（rsfMRI）和早期生长反应 1（EGR1）的全脑免疫组化分析，EGR1 是神经可塑性的标志物，以阐明操作性学习过程中功能网络的时空变化及其潜在的细胞过程。我们使用 11.7-Tesla MRI 扫描仪和 EGR1 的全脑免疫组化分析，在小鼠进行操作性学习的早期和晚期阶段进行。在操作性训练中，当小鼠交替按下左右按钮时，它们会得到奖励，当它们犯错误时，会受到强光惩罚。一组小鼠（n=22）在行为课程之前进行了第一次 rsfMRI 采集，在 3 个训练日之后进行了第二次采集（早期），在 21 个训练日之后进行了第三次采集（晚期）。另一组小鼠（n=40）在行为课程的早期或晚期之后 15 分钟进行了组织学分析。在训练的早期阶段后，边缘区域和丘脑或听觉皮层之间的功能连接增加，在训练的晚期阶段后，运动皮层、感觉皮层和纹状体之间的功能连接增加。在训练的早期和晚期，运动和感觉皮层中 EGR1 免疫阳性细胞的密度都增加了，而杏仁核中的密度仅在训练的早期阶段增加。在早期阶段出现的以边缘区域为中心的亚皮质网络与奖励、愉悦和恐惧有关。在晚期阶段巩固的运动皮层、躯体感觉皮层和纹状体之间的连接与运动学习有关。我们的多模态纵向研究成功地揭示了参与行为学习的脑区的时间变化，以及这些区域之间潜在的细胞水平可塑性。我们的研究代表了朝着建立一种新的实验范式迈出的第一步，该范式将 rsfMRI 和免疫组织化学相结合，将学习涉及的宏观和微观机制联系起来。
