PLoS Com. Bio.：人类大脑“噪音”随年龄而变化
就像陈旧的电视机屏幕上一边跳跃着波动的条纹和雪花似的白点，一边发出嗞嗞的静电噪音，科学家发现我们的大脑也产生噪音。科学家曾猜测，当孩子成长且精神活动更加有效时，这种噪音会下降。但新研究却表明这种噪音随着年龄而加大，表明我们大脑出现了更加复杂的信号。
加拿大多伦多的贝克列斯特（Baycrest）老人护理中心的研究人员让79名志愿者完成了一系列的面部记忆任务，测量他们精确想起每一个面孔的能力如何。参与者有2个年龄组，一组是8—15岁的孩子，另一组是20—33的青壮年。当他们执行任务时，脑电图记录其大脑活动的精确时间。结果发现青壮年一组比孩子们完成任务更加出色。这表明他们的记忆更好，且他们的成绩更加可靠。然而，他们的大脑噪音并不比孩子少，事实上却更多。
负责此项研究的兰迪·麦金托什说：“我们的发现是大脑成熟不仅导致更加稳定和精确的记忆能力，而且也加大了大脑信号的可变性。这不意味着大脑的工作效率在下降，而是表明它们的功能具有更大的可变性，表明神经系统复杂性在加大。”
此研究成果发表在7月4日出版的《公共科学图书馆·计算生物学》（PLoS Computational Biology）上。麦金托什和他的同事目前正开始探寻婴儿和老年人的大脑噪音水平，以全面了解大脑噪音是如何随着年龄而变化的。麦金托什表示，一些证据表明，患上老年痴呆症这类疾病的人，其大脑噪音水平有所下降，而得上精神分裂症一类疾病的人，其大脑噪音水平会有所增加。不过，最理想的大脑噪音水平是什么，现在还不知道。（生物谷Bioon.com）
生物谷推荐原始出处：
PLoS Computational Biology，doi:10.1371/journal.pcbi.1000106，Anthony Randal McIntosh，Roxane J. Itier
Increased Brain Signal Variability Accompanies Lower Behavioral Variability in Development
Rotman Research Institute of Baycrest Centre, University of Toronto, Toronto, Ontario, Canada
Abstract
As the brain matures, its responses become optimized. Behavioral measures show this through improved accuracy and decreased trial-to-trial variability. The question remains whether the supporting brain dynamics show a similar decrease in variability. We examined the relation between variability in single trial evoked electrical activity of the brain (measured with EEG) and performance of a face memory task in children (8–15 y) and young adults (20–33 y). Behaviorally, children showed slower, more variable response times (RT), and less accurate recognition than adults. However, brain signal variability increased with age, and showed strong negative correlations with intrasubject RT variability and positive correlations with accuracy. Thus, maturation appears to lead to a brain with greater functional variability, which is indicative of enhanced neural complexity. This variability may reflect a broader repertoire of metastable brain states and more fluid transitions among them that enable optimum responses. Our results suggest that the moment-to-moment variability in brain activity may be a critical index of the cognitive capacity of the brain.
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