Warren David E, Roembke Tanja C, Covington Natalie V, McMurray Bob, Duff Melissa C
Department of Neurological Sciences, University of Nebraska Medical Center, Omaha, NE, United States.
Institute of Psychology, RWTH Aachen University, Aachen, Germany.
Front Hum Neurosci. 2020 Jan 14;13:448. doi: 10.3389/fnhum.2019.00448. eCollection 2019.
Word learning requires learners to bind together arbitrarily-related phonological, visual, and conceptual information. Prior work suggests that this binding can be robustly achieved incidental cross-situational statistical exposure to words and referents. When cross-situational statistical learning (CSSL) is tested in the laboratory, there is no information on any given trial to identify the referent of a novel word. However, by tracking which objects co-occur with each word across trials, learners may acquire mappings through statistical association. While CSSL behavior is well-characterized, its brain correlates are not. The arbitrary nature of CSSL mappings suggests hippocampal involvement, but the incremental, statistical nature of the learning raises the possibility of neocortical or procedural learning systems. Prior studies have shown that neurological patients with hippocampal pathology have word-learning impairments, but this has not been tested in a statistical learning paradigm. Here, we used a neuropsychological approach to test whether patients with bilateral hippocampal pathology ( = 3) could learn new words in a CSSL paradigm. In the task, patients and healthy comparison participants completed a CSSL word-learning task in which they acquired eight word/object mappings. During each trial of the CSSL task, participants saw two objects on a computer display, heard one novel word, and selected the most likely referent. Across trials, words were 100% likely to co-occur with their referent, but only 14.3% likely with non-referents. Two of three amnesic patients learned the associations between objects and word forms, although performance was impaired relative to healthy comparison participants. Our findings show that the hippocampus is not strictly necessary for CSSL for words, although it may facilitate such learning. This is consistent with a hybrid account of CSSL supported by implicit and explicit memory systems, and may have translational applications for remediation of (word-) learning deficits in neurological populations with hippocampal pathology.
词汇学习要求学习者将任意相关的语音、视觉和概念信息结合在一起。先前的研究表明，通过对单词和所指对象进行偶然的跨情境统计接触，可以有力地实现这种结合。在实验室中测试跨情境统计学习（CSSL）时，任何给定试验中都没有信息来识别新单词的所指对象。然而，通过跟踪每个单词在不同试验中与哪些对象同时出现，学习者可以通过统计关联来习得映射关系。虽然CSSL行为的特征已得到充分描述，但其大脑关联却并不明确。CSSL映射的任意性表明海马体参与其中，但学习的渐进性、统计性又增加了新皮质或程序学习系统参与的可能性。先前的研究表明，患有海马体病变的神经疾病患者存在词汇学习障碍，但这尚未在统计学习范式中得到验证。在此，我们采用神经心理学方法来测试双侧海马体病变患者（n = 3）是否能够在CSSL范式中学习新单词。在该任务中，患者和健康对照参与者完成了一项CSSL词汇学习任务，他们要习得八个单词/对象的映射关系。在CSSL任务的每次试验中，参与者在电脑屏幕上看到两个对象，听到一个新单词，然后选择最有可能的所指对象。在所有试验中，单词与它们的所指对象同时出现的概率为100%，但与非所指对象同时出现的概率仅为14.3%。三名失忆患者中有两名学会了对象与单词形式之间的关联，尽管其表现相对于健康对照参与者有所受损。我们的研究结果表明，海马体对于单词的CSSL并非绝对必要，尽管它可能会促进这种学习。这与由内隐和外显记忆系统支持的CSSL混合理论相一致，并且可能对患有海马体病变的神经疾病人群（单词）学习缺陷的补救具有转化应用价值。
