Center for Mathematics, Computing, and Cognition-Universidade Federal do ABC, Santo André, Brazil.
Department of Psychology, University of Alberta, Edmonton, Alberta, Canada.
J Neurophysiol. 2020 Sep 1;124(3):781-789. doi: 10.1152/jn.00293.2020. Epub 2020 Jul 29.
Significant evidence shows that the acquisition of delay conditioning can occur in out-of-awareness states, such as under anesthesia. However, it is unclear to what extent and what type of conditioning animals may achieve during nonawake states. Trace conditioning is an appealing protocol to study under anesthesia, given the long empty gap separating the conditioned and unconditioned stimuli, which must be bridged for acquisition to happen. Here, we show evidence that rats develop physiological responses during the trace conditioning paradigm under anesthesia. We recorded the activity of the hippocampus (HPC) and lateral entorhinal cortex (LEC) in urethane-anesthetized rats, along with an electromyogram and an electrocardiogram. The protocol consisted of randomly presenting two distinct sound stimuli (CS- and CS+), where only one stimulus (CS+) was assigned to be trace-paired with a footshock. A trial-average analysis revealed that animals developed significant climbing heart rate activity initiating at the CS onset and persisting during the trace period. Such climbing arose for both CS- and CS+ with similar slopes but different intercepts, suggesting CS+ heart rates were typically above CS-. The power and coherence of HPC and LEC high-frequency bands (>100 Hz) significantly increased during CS presentation and trace, similarly to CS- and CS+ and insensitive to either activated or deactivated states. To the best of our knowledge, this is the first attempt to perform a trace conditioning protocol under anesthesia. Confirmation of this procedure acquisition can allow a new preparation for the exploration of brain mechanisms that bind time-discontinuous events. Some forms of learning, such as some types of conditioning, can occur in anesthetized states. However, the extent to which memories can be formed in these states is still an open question. Here, we investigated the trace conditioning under urethane anesthesia and found heart rate, hippocampus, and lateral entorhinal cortex physiological changes to stimuli presentation. This new preparation may allow for exploration of memory acquisition of time-discontinuous events in the nonawake brain.
大量证据表明，在无意识状态下，如麻醉状态下，也可以获得延迟条件反射。然而，在非清醒状态下，动物能达到何种程度和何种类型的条件反射尚不清楚。痕迹条件反射是一种在麻醉状态下很有吸引力的研究方案，因为条件刺激和非条件刺激之间存在很长的空白间隔，必须通过这种间隔才能发生获得。在这里，我们证明了在麻醉状态下，大鼠在痕迹条件反射范式中会产生生理反应。我们在氨基甲酸乙酯麻醉的大鼠中记录了海马体（HPC）和外侧内嗅皮层（LEC）的活动，同时记录了肌电图和心电图。该方案包括随机呈现两种不同的声音刺激（CS-和 CS+），其中只有一种刺激（CS+）被分配与足部电击进行痕迹配对。试验平均分析显示，动物在 CS 开始时出现明显的心跳加速活动，并在痕迹期持续存在。这种心跳加速在 CS-和 CS+中都出现了，斜率相似，但截距不同，这表明 CS+的心率通常高于 CS-。CS 呈现和痕迹期间，HPC 和 LEC 高频带（>100 Hz）的功率和相干性显著增加，与 CS-和 CS+相似，且不受激活或去激活状态的影响。据我们所知，这是首次在麻醉状态下尝试进行痕迹条件反射方案。确认这种程序的获得可以为探索将时间不连续事件联系起来的大脑机制提供一种新的准备。某些形式的学习，如某些类型的条件反射，可以在麻醉状态下发生。然而，在这些状态下可以形成记忆的程度仍然是一个悬而未决的问题。在这里，我们研究了在氨基甲酸乙酯麻醉下的痕迹条件反射，发现了刺激呈现时心率、海马体和外侧内嗅皮层的生理变化。这种新的准备可能允许在非清醒大脑中探索时间不连续事件的记忆获得。
