Hofstetter Shir, Friedmann Naama, Assaf Yaniv
Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.
Language and Brain Lab, School of Education, Tel Aviv University, Tel Aviv, Israel.
Brain Struct Funct. 2017 Apr;222(3):1231-1241. doi: 10.1007/s00429-016-1273-2. Epub 2016 Jul 23.
Human brain imaging revealed that the brain can undergo structural plasticity following new learning experiences. Most magnetic resonance imaging (MRI) uncovered morphometric alternation in cortical density after the long-term training of weeks to months. A recent diffusion tensor imaging (DTI) study has found changes in diffusion indices after 2 h of training, primarily in the hippocampus. However, whether a short learning experience can induce microstructural changes in the neocortex is still unclear. Here, we used diffusion MRI, a method sensitive to tissue microstructure, to study cortical plasticity. To attain cortical involvement, we used a short language task (under 1 h) of introducing new lexical items (flower names) to the lexicon. We have found significant changes in diffusivity in cortical regions involved in language and reading (inferior frontal gyrus, middle temporal gyrus, and inferior parietal lobule). In addition, the difference in the values of diffusivity correlated with the lexical learning rate in the task. Moreover, significant changes were found in white matter tracts near the cortex, and the extent of change correlated with behavioral measures of lexical learning rate. These findings provide first evidence of short-term cortical plasticity in the human brain after a short language learning task. It seems that short training of less than an hour of high cognitive demand can induce microstructural changes in the cortex, suggesting a rapid time scale of neuroplasticity and providing additional evidence of the power of MRI to investigate the temporal and spatial progressions of this process.
人类大脑成像显示，大脑在经历新的学习体验后会发生结构可塑性变化。大多数磁共振成像（MRI）研究发现，经过数周至数月的长期训练后，皮质密度会出现形态学改变。最近一项扩散张量成像（DTI）研究发现，经过2小时的训练后，扩散指数发生了变化，主要发生在海马体。然而，短暂的学习体验是否能诱导新皮质的微观结构变化仍不清楚。在此，我们使用对组织微观结构敏感的扩散MRI方法来研究皮质可塑性。为了使皮质参与其中，我们使用了一项简短的语言任务（不到1小时），向词汇表中引入新的词汇项目（花名）。我们发现，参与语言和阅读的皮质区域（额下回、颞中回和顶下小叶）的扩散率发生了显著变化。此外，扩散率值的差异与任务中的词汇学习率相关。此外，在皮质附近的白质束中也发现了显著变化，变化程度与词汇学习率的行为测量结果相关。这些发现首次证明了人类大脑在经过简短的语言学习任务后会出现短期皮质可塑性。似乎不到一小时的高认知需求的短期训练就能诱导皮质的微观结构变化，这表明神经可塑性的时间尺度很快，并为MRI研究这一过程的时间和空间进展的能力提供了额外证据。
