关键词： 生物研究

科研人员报告说，大脑的人脸视觉处理系统在生命早期的一个增强了的神经可塑性时期进行了微调。此前的研究提示这样一个时期在生命的头几个月存在，但是究竟神经回路是新建立的还是仅仅在这个时期进行了调整还不清楚。为了回答这个问题，Brigitte Röder及其同事研究了出生失明、至多14年后视力恢复的11个人，并且研究了匹配的健康受试者以及有部分视力的受试者。在一次持续的脑电图检测中，这组作者记录下了受试者对人脸及房屋的完整的和混乱的照片做出响应的事件相关性电位。该研究表明尽管所有的受试者都可以识别这些照片，但是无论有没有向曾在出生时失明的人展示人脸或房屋的照片，他们都会出现一个被称为N170的电位——它通常是在对人脸做出响应的时候才出现的。相比之下，健康人和有部分视力的受试者仅仅在对人脸做出响应的时候才出现了N170电位。这组作者说，这些发现揭示出了人类出生就拥有面部处理系统的基本神经回路，但是大脑依赖于生命早期的视觉经验微调这些神经回路，从而增强对视觉的处理。

推荐的英文摘要

PNAS doi: 10.1073/pnas.1309963110

Sensitive periods for the functional specialization of the neural system for human face processing

Brigitte Rödera,1, Pia Leya, Bhamy H. Shenoyb, Ramesh Kekunnayab, ａnd Davide Bottari

The aim of the study was to identify possible sensitive phases in the development of the processing system for human faces. We tested the neural processing of faces in 11 humans who had been blind from birth ａnd had undergone cataract surgery between 2 mo ａnd 14 y of age. Pictures of faces ａnd houses, scrambLED versions of these pictures, ａnd pictures of butterflies were presented while event-related potentials were recorded. Participants had to respond to the pictures of butterflies （targets） only. All participants, even those who had been blind from birth for several years, were able to categorize the pictures ａnd to detect the targets. In healthy controls ａnd in a group of visually impaired individuals with a history of developmental or incomplete congenital cataracts, the well-known enhancement of the N170 （negative peak around 170 ms） event-related potential to faces emerged, but a face-sensitive response was not observed in humans with a history of congenital dense cataracts. By contrast, this group showed a similar N170 response to all visual stimuli, which was indistinguishable from the N170 response to faces in the controls. The face-sensitive N170 response has been associated with the structural encoding of faces. Therefore, these data provide evidence for the hypothesis that the functional differentiation of category-specific neural representations in humans, presumably involving the elaboration of inhibitory circuits, is dependent on experience ａnd linked to a sensitive period. Such functional specialization of neural systems seems necessary to archive high processing proficiency.