Mair Robert G, Francoeur Miranda J, Gibson Brett M
Department of Psychology, University of New Hampshire, Durham, NH, United States.
Neural Engineering and Translation Lab, University of California, San Diego, San Diego, CA, United States.
Front Behav Neurosci. 2021 Apr 8;15:642204. doi: 10.3389/fnbeh.2021.642204. eCollection 2021.
The medial prefrontal cortex (mPFC) has robust afferent and efferent connections with multiple nuclei clustered in the central thalamus. These nuclei are elements in large-scale networks linking mPFC with the hippocampus, basal ganglia, amygdala, other cortical areas, and visceral and arousal systems in the brainstem that give rise to adaptive goal-directed behavior. Lesions of the mediodorsal nucleus (MD), the main source of thalamic input to middle layers of PFC, have limited effects on delayed conditional discriminations, like DMTP and DNMTP, that depend on mPFC. Recent evidence suggests that MD sustains and amplifies neuronal responses in mPFC that represent salient task-related information and is important for detecting and encoding contingencies between actions and their consequences. Lesions of rostral intralaminar (rIL) and ventromedial (VM) nuclei produce delay-independent impairments of egocentric DMTP and DNMTP that resemble effects of mPFC lesions on response speed and accuracy: results consistent with projections of rIL to striatum and VM to motor cortices. The ventral midline and anterior thalamic nuclei affect allocentric spatial cognition and memory consistent with their connections to mPFC and hippocampus. The dorsal midline nuclei spare DMTP and DNMTP. They have been implicated in behavioral-state control and response to salient stimuli in associative learning. mPFC functions are served during DNMTP by discrete populations of neurons with responses related to motor preparation, movements, lever press responses, reinforcement anticipation, reinforcement delivery, and memory delay. Population analyses show that different responses are timed so that they effectively tile the temporal interval from when DNMTP trials are initiated until the end. Event-related responses of MD neurons during DNMTP are predominantly related to movement and reinforcement, information important for DNMTP choice. These responses closely mirror the activity of mPFC neurons with similar responses. Pharmacological inactivation of MD and adjacent rIL affects the expression of diverse action- and outcome-related responses of mPFC neurons. Lesions of MD before training are associated with a shift away from movement-related responses in mPFC important for DNMTP choice. These results suggest that MD has short-term effects on the expression of event-related activity in mPFC and long-term effects that tune mPFC neurons to respond to task-specific information.
内侧前额叶皮质（mPFC）与聚集在丘脑中央的多个核团有着强大的传入和传出连接。这些核团是大规模网络的组成部分，该网络将mPFC与海马体、基底神经节、杏仁核、其他皮质区域以及脑干中的内脏和觉醒系统相连，从而产生适应性的目标导向行为。丘脑背内侧核（MD）是PFC中层丘脑输入的主要来源，其损伤对依赖mPFC的延迟条件辨别（如延迟匹配-样本任务和延迟不匹配-样本任务）影响有限。最近的证据表明，MD维持并放大了mPFC中代表显著任务相关信息的神经元反应，并且对于检测和编码动作与其后果之间的偶发事件很重要。嘴侧层内（rIL）核和腹内侧（VM）核的损伤会导致以自我为中心的延迟匹配-样本任务和延迟不匹配-样本任务出现与延迟无关的损伤，这类似于mPFC损伤对反应速度和准确性的影响：结果与rIL向纹状体和VM向运动皮层的投射一致。腹侧中线和前丘脑核影响以自我为中心的空间认知和记忆，这与其与mPFC和海马体的连接相符。背侧中线核不影响延迟匹配-样本任务和延迟不匹配-样本任务。它们与行为状态控制以及在联想学习中对显著刺激的反应有关。在延迟不匹配-样本任务期间，mPFC的功能由不同的神经元群体完成，这些神经元的反应与运动准备、运动、杠杆按压反应、强化预期、强化给予和记忆延迟有关。群体分析表明，不同的反应是定时的，以便它们有效地覆盖从延迟不匹配-样本任务试验开始到结束的时间间隔。延迟不匹配-样本任务期间MD神经元的事件相关反应主要与运动和强化有关，这对延迟不匹配-样本任务的选择很重要。这些反应紧密反映了具有相似反应的mPFC神经元的活动。MD和相邻rIL的药理学失活会影响mPFC神经元各种与动作和结果相关反应的表达。训练前MD的损伤与mPFC中对延迟不匹配-样本任务选择很重要的与运动相关反应的转变有关。这些结果表明，MD对mPFC中事件相关活动的表达有短期影响，并且对调整mPFC神经元以响应特定任务信息有长期影响。
