Center for Sleep and Circadian Neurobiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA.
Front Mol Neurosci. 2012 Feb 28;5:23. doi: 10.3389/fnmol.2012.00023. eCollection 2012.
Evolutionarily, what was the earliest engram? Biology has evolved to encode representations of past events, and in neuroscience, we are attempting to link experience-dependent changes in molecular signaling with cellular processes that ultimately lead to behavioral output. The theory of evolution has guided biological research for decades, and since phylogenetically conserved mechanisms drive circadian rhythms, these processes may serve as common predecessors underlying more complex behavioral phenotypes. For example, the cAMP/MAPK/CREB cascade is interwoven with the clock to trigger circadian output, and is also known to affect memory formation. Time-of-day dependent changes have been observed in long-term potentiation (LTP) within the suprachiasmatic nucleus and hippocampus, along with light-induced circadian phase resetting and fear conditioning behaviors. Together this suggests during evolution, similar processes underlying metaplasticity in more simple circuits may have been redeployed in higher-order brain regions. Therefore, this notion predicts a model that LTP and metaplasticity may exist in neural circuits of other species, through phylogenetically conserved pathways, leading to several testable hypotheses.
从进化的角度来看，最早的记忆痕迹是什么？生物学已经进化到可以对过去事件进行编码，而在神经科学中，我们试图将依赖经验的分子信号变化与最终导致行为输出的细胞过程联系起来。进化理论指导了生物学研究几十年，由于进化上保守的机制驱动着昼夜节律，这些过程可能是更复杂的行为表型的共同前身。例如，cAMP/MAPK/CREB 级联与生物钟交织在一起，触发昼夜节律输出，并且已知还会影响记忆形成。在视交叉上核和海马体中观察到长时程增强（LTP）的昼夜节律变化，以及光诱导的昼夜节律相位重置和恐惧条件反射行为。这表明，在进化过程中，在更简单的电路中调节记忆痕迹可塑性的类似过程可能已经在更高阶的大脑区域重新部署。因此，这一概念预测了一个模型，即 LTP 和记忆痕迹可塑性可能存在于其他物种的神经回路中，通过进化上保守的途径，产生了几个可测试的假设。
