理智之声需要血清素
如果有更多的神经传递素—血清素，易怒的人就能冷静下来。研究人员给19位健康的志愿者一份能够降低他们血清素水平的日常饮食，并然后扫描他们的大脑。他们发现，大脑产生恐惧感的扁桃体区域之间的通讯及对前额皮质的控制都降低了。这可能导致对中等的威胁采取不恰当的暴力反应。
通过在志愿者进行功能性MRI大脑扫描时展示带着愤怒、悲伤或中性面部表情的低血清素志愿者的图片，研究小组发现了这一效果。这些志愿者们被要求说出这些每个图像是男人或者女人的，但是真正的意图是查看他们的大脑对以愤怒面孔摆出的威胁姿态作出的反应。
扫描显示，在所有的志愿者中，当他们看到愤怒面孔时，扁桃体和前额皮质之间的关联性降低。这种效果在那些通过调查问卷发现具有暴力倾向的人当中最为明显。“就好像丢失了理智的调解声，”团队的领导人、意大利卡坦札罗的Luca Passamonti说。
生物探索推荐英文论文摘要：
Effects of Acute Tryptophan Depletion on Prefrontal-Amygdala Connectivity While Viewing Facial Signals of Aggression
Background Reduced levels of serotonin (5-HT) within prefrontal cortex (PFC)–amygdala circuits have long been implicated in impulsive aggression. However, whether lowering 5-HT alters the dynamic interplay between the PFC and the amygdala has not been directly tested in humans. It is known that manipulating 5-HT via acute tryptophan depletion (ATD) causes variable effects on brain responses to a variety of emotional stimuli, but it remains unclear whether ATD affects functional connectivity in neural networks involved in processing social signals of aggression (e.g., angry faces).
Methods Thirty healthy individuals were enrolled in a randomized, double-blind, placebo-controlled ATD study. On each treatment, brain responses to angry, sad, and neutral faces were measured with functional magnetic resonance imaging. Two methods (psycho-physiological-interaction in a general linear model and dynamic causal modeling) were used to assess the impact of ATD on the functional connectivity between PFC and amygdala.
Results Data from 19 subjects were available for the final analyses. A whole-brain psycho-physiological-interaction in a general linear model showed that ATD significantly modulated the connectivity between the amygdala and two PFC regions (ventral anterior cingulate cortex and ventrolateral PFC) when processing angry vs. neutral and angry vs. sad but not sad vs. neutral faces. Dynamic causal modeling corroborated and extended these findings by showing that 5-HT depletion reduced the influence of processing angry vs. neutral faces on circuits within PFC and on PFC–amygdala pathways.
Conclusions We provide strong support for neurobiological accounts positing that 5-HT significantly influences PFC–amygdala circuits implicated in aggression and other affective behaviors.
