一孕傻3年~脑功能MRI提供科学依据（翻译版在这里）
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经常有人说一孕傻三年，意思是当女性怀孕后，记忆力会有衰退的迹象，常常会丢三落四，通常我们叫此为“孕傻”或“婴儿脑”状态。
近日，Nat Neurosci杂志在线发表了一项持续5年多的研究，为一孕傻3年的原因提供了科学的依据。研究纳入第一次怀孕前后的妈妈和未产妇进行对照比较，通过脑结构MRI发现怀孕妈妈存在着社会认知相关脑区的脑灰质体积减少。有意思的是这种减少可以预测产后母性表现，表明这种调节机制服务于母爱的转化。研究者通过随访研究发现这种灰质体积减少至少持续至产后2年以上，这也解释了我们常说的一孕傻3年。
剖析式的扫描发现怀孕让大脑灰质减少
研究人员对备孕头胎的25名妇女的大脑进行了剖析式的扫描，在这些妇女分娩后两个月左右进行了更多的扫描。怀孕留下的印记是如此强烈，研究人员甚至可以根据她们大脑的变化来预测女性是否怀孕过。
这些怀着孩子及分娩后的妇女与20名没有怀孕的妇女、19名新爸爸和17名没有孩子的男性相比在大脑某些区域有较少的灰质，这些变化在怀孕两年后仍然明显。
文章的作者之一，如今在荷兰Leiden大学的神经科学家Elseline Hoekzema（文章大部分研究工作是他之前在巴塞罗那的Autònoma de大学完成的）说：“灰质的减少并不一定是坏事。类似的减少发生在青春期，是一个对正常认知和情感发展至关重要的细化阶段。”除了那些重要的青少年时期，怀孕几乎被认为是大脑成熟的第二个阶段。
怀孕改变某些脑区让新妈妈对婴儿更敏感
进一步的实验表明，怀孕期间以一个非常特别的方式塑造母亲的大脑，能让女性更加适应他们无助的婴儿。缩小最多的区域——额叶和颞叶皮质部分以及中线，被认为是参与到别人的心理预测的脑区。这种选择性收缩可能表明，作为怀孕的结果，这些地区变得更加专业化，更高效率帮助一个新的母亲更好地照顾一个婴儿。
改变最多的大脑区域也显示了对她们的婴儿照片的巨大反应。另外，大脑变化最多的女性在她们对婴儿的依恋问卷中得分更高。
而新爸爸却没有表现出这样的大脑变化。这一结果表明，对母亲大脑的影响并不是由社会地位突变成父母而造成的。这不是由于有一个孩子要照顾让大脑产生的变化。
大脑的变化可能是由妊娠激素如雌激素和孕激素引起的。怀孕是大量激素进入大脑的期间，但是有科学家指出该文章并没有真正研究怀孕期间大脑，只是研究了之前和之后。所以现在并不知道这种变化是何时发生的，出生时激素的急剧下降也可能重塑大脑。
Figure 2 Means of conception. Surface maps of GM volume changes between the Pre and Post session (P < 0.05, FWE-corrected) in (a) the primiparous women achieving pregnancy by natural conception (N = 9), (b) primiparous women achieving pregnancy by fertility treatment(N = 16), and (c) the nulliparous control women (N = 20).
Figure 3 Classification. (a) Scatter plot depicting the support vector machine classification results. Function values (mean ± s.d.): FPRG: 1.27 ± 1.03, FCTR: −0.79 ± 0.33. Balanced accuracy: 100%, although some participants are close to the decision function border; dashed line is the function value cut-off between classes (0), leave-one-out cross-validation, Npermutations = 10,000, P ≤ 0.0001. Function values are plotted per fold (i.e., in this case, per subject). (b) Weight map for the classifier, depicting the relative contribution of the voxel to the decision function. (c) Weight maps for the regions of greatest predictive power resulting from the multiple-kernel learning model using the Automated Anatomical Labeling (AAL) atlas (balanced accuracy: 93.5%, leave-one-out cross-validation, Npermutations = 10,000, P ≤ 0.0001). These are (depicted from left to right) the right middle temporal gyrus (weight 22.46%, experimental ranking 1.2), the right inferior frontal gyrus (weight 19.46%, experimental ranking 1.84)
and the right posterior cingulate cortex (weight 10.41%, experimental ranking 3.98). FCTR, nulliparous control women who were not pregnant between sessions; FPRG, nulliparous women who became pregnant and gave birth between sessions.
Figure 4 Similarity between theory-of-mind network and GM volume changes of pregnancy. (a) The theory-of-mind network as extracted from the meta-analysis by Schurz et al.22. Statistical map of permutation-based z-values of the pooled meta-analysis was provided by Schurz et al.22 and displayed using Caret software. (b) Reductions in GM volume (P < 0.05, FWE-corrected) in the group of women who were pregnant between sessions in the current study.
Figure 5 Surface-based measures. Surface maps depicting changes in (a) surface area and (b) cortical thickness across pregnancy (false discovery rate (FDR)-corrected P < 0.05). Blue and cyan reflect increases while red and yellow reflect decreases.
Figure 6 Postpartum infant-related neural activity and attachment scores. (a) fMRI results for the ‘own > other baby’ contrast (N = 20) alongside GM volume changes repeated from Figure 1. For illustrative purposes, the fMRI results are depicted at the more lenient threshold of P < 0.0001 uncorrected (the right inferior frontal cluster and a trend for the posterior cingulate cortex are observed at the P < 0.05 FWE-corrected threshold; see Supplementary Table 11). There were no statistically significant results for the ‘other > own’ baby pictures contrast at either threshold. (b) Multivariate prediction of Maternal Postpartum Attachment Scale (MPAS) scores based on the GM volume changes of pregnancy. Multivariate kernel ridge regression results (N = 24, leave-one-out cross-validation) with the MPAS scores (Npermutations = 10,000. Quality of attachment: mean ± s.d. = 37.11 ± 3.99. P = 0.030, pnMSE = 0.024. Absence of hostility: mean ± s.d. = 16.93 ± 4.10. P = 0.026, pnMSE = 0.021. Pleasure in interaction: mean ± s.d. = 20.88 ± 3.10. P = 0.985, pnMSE = 0.918). Predicted versus actual MPAS scores are plotted for the two MPAS scores that were found to be associated with the GM volume changes; nMSE, normalized mean squared error.
Figure 7 Long-term follow-up. (a) Mean (± s.e.m.) signal change at each Post session relative to the Pre baseline, extracted from the smoothed normalized jacobian difference images. The remaining clusters are plotted in Supplementary Figure 1. (b) Surface maps depicting GM volume reductions in the Post +2 years session compared to the Pre baseline (P < 0.05 FWE-corrected). Complete Pre, Post and Post + 2 years data sets were available of 11 women.(c) Mean signal change in the Post session compared to the pre-pregnancy baseline in the left hippocampal cluster and sagittal slice depicting hippocampal cluster from Post versus Pre comparison. (d) Plot (mean ± s.e.m.) and sagittal overlay depicting hippocampal recovery from the Post to the Post + 2 years session. Statistics are reported in Supplementary Table 13. Sup. Temp., superior temporal; Inf., inferior; Med., medial; L, left; R, right. FCTR, nulliparous control women who were not pregnant between sessions; FPRG, nulliparous women who became pregnant and gave birth between sessions.
参考资料：
Pregnancy linked to long-term changes in mom’s brain
Pregnancy changes mother's brain structure, study shows
原文：Hoekzema E, Barba-Müller E, Pozzobon C, et al. Pregnancy leads to long-lasting changes in human brain structure.Nat Neurosci. 2016 Dec 19.[Epub ahead of print]
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