Soares Ana Paula, Gutiérrez-Domínguez Francisco-Javier, Vasconcelos Margarida, Oliveira Helena M, Tomé David, Jiménez Luis
Human Cognition Lab, CIPsi, School of Psychology, University of Minho, Braga, Portugal.
Psychological Neuroscience Lab, CIPsi, School of Psychology, University of Minho, Braga, Portugal.
Front Hum Neurosci. 2020 Sep 23;14:577991. doi: 10.3389/fnhum.2020.577991. eCollection 2020.
Statistical learning (SL), the process of extracting regularities from the environment, is a fundamental skill of our cognitive system to structure the world regularly and predictably. SL has been studied using mainly behavioral tasks under implicit conditions and with triplets presenting the same level of difficulty, i.e., a mean transitional probability (TP) of 1.00. Yet, the neural mechanisms underlying SL under other learning conditions remain largely unknown. Here, we investigated the neurofunctional correlates of SL using triplets (i.e., three-syllable nonsense words) with a mean TP of 1.00 () and 0.50 () in an SL task performed under incidental (implicit) and intentional (explicit) conditions, to determine whether the same core mechanisms were recruited to assist learning. Event-related potentials (ERPs) were recorded while participants listened firstly to a continuous auditory stream made of the concatenation of four easy and four hard "words" under implicit instructions, and subsequently to another auditory stream made of the concatenation of four easy and four hard "words" drawn from another artificial language under explicit instructions. The stream in each of the SL tasks was presented in two consecutive blocks of 3.5-min each (7-min in total) to further examine how ERP components might change over time. Behavioral measures of SL were collected after the familiarization phase of each SL task by asking participants to perform a two-alternative forced-choice (2-AFC) task. Results from the 2-AFC tasks revealed a moderate but reliable level of SL, with no differences between conditions. ERPs were, nevertheless, sensitive to the effect of TPs, showing larger amplitudes of N400 for easy "words," as well as to the effect of instructions, with a reduced N250 for "words" presented under explicit conditions. Also, significant differences in the N100 were found as a result of the interaction between TPs, instructions, and the amount of exposure to the auditory stream. Taken together, our findings suggest that triplets' predictability impacts the emergence of "words" representations in the brain both for statistical regularities extracted under incidental and intentional instructions, although the prior knowledge of the "words" seems to favor the recruitment of different SL mechanisms.
统计学习（SL）是从环境中提取规律的过程，是我们认知系统以规律且可预测的方式构建世界的一项基本技能。对统计学习的研究主要采用隐含条件下的行为任务，且三元组呈现相同的难度水平，即平均转移概率（TP）为1.00。然而，在其他学习条件下统计学习背后的神经机制仍 largely unknown。在此，我们在偶然（隐含）和有意（明确）条件下进行的统计学习任务中，使用平均TP为1.00（）和0.50（）的三元组（即三音节无意义单词）来研究统计学习的神经功能相关性，以确定是否调用相同的核心机制来辅助学习。记录事件相关电位（ERP），参与者首先在隐含指令下聆听由四个简单和四个复杂“单词”串联而成的连续听觉流，随后在明确指令下聆听由从另一种人工语言中抽取的四个简单和四个复杂“单词”串联而成的另一个听觉流。每个统计学习任务中的流以两个连续的约3.5分钟块呈现（总共约7分钟），以进一步检查ERP成分如何随时间变化。在每个统计学习任务的熟悉阶段之后，通过要求参与者执行二选一强制选择（2-AFC）任务来收集统计学习的行为测量数据。2-AFC任务的结果显示出适度但可靠的统计学习水平，各条件之间无差异。然而，ERP对转移概率的影响敏感，对于简单“单词”显示出更大的N400振幅，并对指令的影响敏感——在明确条件下呈现的“单词”的N250减小。此外，由于转移概率、指令和听觉流暴露量之间的相互作用，在N100中发现了显著差异。综上所述，我们的研究结果表明，三元组的可预测性会影响在偶然和有意指令下提取的统计规律在大脑中出现“单词”表征，尽管对“单词”的先验知识似乎有利于调用不同的统计学习机制。
