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 (easy “words”) and 0.50 (hard “words”) 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.

中文翻译：

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并非所有单词的习得均等：过渡概率和指令影响统计学习的电生理相关性


统计学习（SL）是从环境中提取规律的过程，是我们认知系统有规律地、可预测地构建世界的基本技能。 SL 主要使用隐式条件下的行为任务进行研究，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，其他学习条件下 SL 的神经机制仍然很大程度上未知。在这里，我们在偶然（隐性）下执行的 SL 任务中使用平均 TP 为 1.00（简单“单词”）和 0.50（困难“单词”）的三连音（即三音节无意义单词）来研究 SL 的神经功能相关性。和有意（显式）条件，以确定是否招募相同的核心机制来协助学习。事件相关电位（ERP）被记录下来，参与者首先聆听由四个简单和四个困难“单词”在隐含指令下串联而成的连续听觉流，随后聆听由四个简单和四个困难“单词”串联而成的另一个听觉流。在明确的指令下从另一种人工语言中提取的硬“词”。每个 SL 任务中的流以两个连续块的形式呈现，每个块大约 3.5 分钟（总共大约 7 分钟），以进一步检查 ERP 组件如何随时间变化。在每个 SL 任务的熟悉阶段后，通过要求参与者执行两个替代的强制选择 (2-AFC) 任务来收集 SL 的行为测量。 2-AFC 任务的结果显示了中等但可靠的 SL 水平，条件之间没有差异。 然而，ERP 对 TP 的影响很敏感，对于简单的“单词”，显示出较大的 N400 幅度；对于指令的效果，ERP 也很敏感，在明确的条件下，“单词”的 N250 会降低。此外，由于 TP、指令和听觉流暴露量之间的相互作用，我们发现 N100 存在显着差异。总而言之，我们的研究结果表明，三胞胎的可预测性会影响大脑中“单词”表征的出现，无论是在偶然的还是有意的指令下提取的统计规律，尽管“单词”的先验知识似乎有利于招募不同的 SL 机制。