主页 > 医学新闻 >
【科普】PNAS：大脑发育解释缘何“青春无畏”
美国康奈尔大学、布朗大学和纽约州立大学医学院学者的一项联合医学研究发现，在一些哺乳动物青春期时，大脑发生变化，产生一种恐惧记忆抑制效应，使动物对恐惧经历的记忆力降低，进而表现为一种无所畏惧、敢于再次冒险的性格现象。
研究者在实验室对实验鼠展开反复实验，让不同年龄段的实验鼠经历触电和强噪音两类“打击”。隔一段时间后，再让这批实验鼠进入相同环境，结果发现，无所畏惧再次触电或再次进入强噪音环境的实验鼠大多为处于青春期的实验鼠。
幼鼠和成年鼠对过往经历的记忆明显优于青春期实验鼠。
这一研究结果发表在1月10日出版的美国《国家科学院院刊》（PNAS）上。
对实验鼠大脑活动检测显示，青春期哺乳动物大脑内的“杏仁核”与“海马体”两个部分表现出非活跃状态。“杏仁核”与“海马体”位于大脑底部，前者是大脑的情绪中心，管理与储存各种情绪反应，后者负责管理情境记忆。
文章中，研究者认为，并非青春期哺乳动物不懂害怕，而是这一时期的大脑产生了抑制恐惧效应。并非青春期的孩子故意反复犯错惹父母生气，而是大脑发育到这一阶段使孩子们对恐惧感“暂时性失忆”。
这种大脑效应只在青春期出现，随着年龄增长及大脑进一步发育而消失。
研究者说，这一发现不仅有助于了解青春期少年，而且也将对成年人的疾病治疗产生积极意义，有可能辅助治疗那些在承受外部打击后出现恐惧症和忧虑紊乱症的患者。 Abstract
Highly conserved neural circuitry between rodents and humans has allowed for in-depth characterization of behavioral and molecular processes associated with emotional learning and memory. Despite increased prevalence of affective disorders in adolescent humans, few studies have characterized how associative-emotional learning changes during the transition through adolescence or identified mechanisms underlying such changes. By examining fear conditioning in mice, as they transitioned into and out of adolescence, we found that a suppression of contextual fear occurs during adolescence. Although contextual fear memories were not expressed during early adolescence, they could be retrieved and expressed as the mice transitioned out of adolescence. This temporary suppression of contextual fear was associated with blunted synaptic activity in the basal amygdala and decreased PI3K and MAPK signaling in the hippocampus. These findings reveal a unique form of brain plasticity in fear learning during early adolescence and may prove informative for understanding endogenous mechanisms to suppress unwanted fear memories. [标签:content2]
阅读本文的人还阅读：
作者:admin@医学,生命科学 2011-01-12 23:22
医学,生命科学网