wiki笔记--nucleus accumbens core--2021/11/27

Core[edit]

The nucleus accumbens core (NAcc core) is the inner substructure of the nucleus accumbens.

Location: The nucleus accumbens core is part of the ventral striatum, located within the basal ganglia. Cell types: The core of the NAcc is made up mainly of medium spiny neurons containing mainly D1-type or D2-type dopamine receptors. The D1-type medium spiny neurons mediate reward-related cognitive processes,[5][35][36] whereas the D2-type medium spiny neurons mediate aversion-related cognition.[6] The neurons in the core, as compared to the neurons in the shell, have an increased density of dendritic spines, branch segments, and terminal segments. From the core, the neurons project to other sub-cortical areas such as the globus pallidus and the substantia nigra.

（在globus pallidus中，外侧苍白球活动抑制底丘脑核从而不去兴奋内侧苍白球，也就是说外侧苍白球活动的效果是不兴奋内侧苍白球，对于行为来说，外侧苍白球活动是有利于行为的产生，而内侧苍白球的活动是不利于行为的产生；在黑质中，reticulata部分活动不利于行为的产生，而compacta部分活动利于行为的产生。那么nucleus accumbens core中的D1-type medium spiny neurons与D2-type medium spiny neurons很有可能是分别投射到上述列举的结构，具体为D2-type medium spiny neurons投射抑制轴突到外侧苍白球、compacta部分，mediate aversion-related cognition；D1-type medium spiny neurons投射抑制轴突到内侧苍白球、reticulata部分，mediate reward-related cognitive processes，这时reticulata部分被一定程度抑制，这是可以一定程度反映在眼球转动和生理欲望的出现上，也就是说得到reward时，眼球很容易出现转动现象，至少是不那么直勾勾，pedunculopontine nucleus也不那么被抑制，能够投射出更多的aectylcholine递质进行广泛影响，从而不自觉地产生心理活动（类似于，哥们儿，得大奖了，说一下获奖感言吧。显然根据自身经验，得到reward时，内心总会有明确的感受出现，所以会问出感受如何的话。）。这意味着VTA通过多巴胺系统可以同时主导reward-related cognitive processes和aversion-related cognition，不过这种aversion-related cognition是区别于lateral habenula

导致的惩罚行为，因为lateral habenula同时抑制多巴胺系统、serotonin系统、acetylcholine系统，或者说个体之间逗闹中的躲避、害怕行为就是由VTA主导aversion-related cognition产生的。而nucleus accumbens core 中的D2-type medium spiny neurons又属于sleep-promoting nuclei，即可以被adenosine兴奋，产生睡眠倾向。我观察到秀秀两岁半之前存在这样的现象：她太调皮，我极为大声呵斥她，她会郁闷地跑去蒙头，然后很快就睡过去了，这种情况出现过很多次，她的睡眠行为与被大声呵斥而多巴胺系统被打压有因果关系。类似的，我也听说过很多别人受委屈而去蒙头睡觉的例子，我觉得其中的机制很有可能就是VTA被委屈抑制，然后nucleus accumbens core 中的D2-type medium spiny neurons能够对adenosine敏感，再加上蒙头导致血管中二氧化碳浓度增加，从而增加了raphe nucleus的活动，从而降低了大脑皮层与丘脑的放电量，进一步降低了arousal system接收大脑皮层的信号量，导致adenosine兴奋各处的sleep-promoting nuclei，导致人进入睡眠状态。）

 GABA is one of the main neurotransmitters in the NAcc, and GABA receptors are also abundant.[27][29]

Function: The nucleus accumbens core is involved in the cognitive processing of motor function related to reward and reinforcement and the regulation of slow-wave sleep.[4][11][12][13] Specifically, the core encodes new motor programs which facilitate the acquisition of a given reward in the future.[4] The indirect pathway (i.e., D2-type) neurons in the NAcc core which co-express adenosine A2A receptors activation-dependently promote slow-wave sleep.[11][12][13] The NAcc core has also been shown to mediate general Pavlovian-instrumental transfer, a phenomenon in which a classically conditioned stimulus modifies operant behavior.[32][9][10]

这一篇文章中干货内容十足，揭示几种重要的行为内在机制，而且可以用来验证的手段可谓遍地都是，随手就有，毕竟这里涉及到了sleep-promoting nuclei和reward-related cognitive processes和aversion-related cognition。而且，我还给出了解剖学上连接结构的预测，即D1-type medium spiny neurons 和D2-type medium spiny neurons投射到basal forebrain中的具体位置，从而对应着reward-related cognitive processes和aversion-related cognition。