The neural correlates of nominal classification rule learning and their individual differences

Learning a second language involves not only the acquisition of abstract grammatical rules, such as word order, but also rules based on language-specific semantic distinctions, as seen in nominal classification systems. However, little is known about the neural mechanisms underlying learning of such systems. The present study examined the neural correlates of nominal classification rule learning and the role of individual differences in working memory and language analytic ability. 36 adult Japanese native speakers learned a semi-artificial language incorporating nominal classification rules (animate, small inanimate and large inanimate). Brain activation was measured using fMRI across three learning phases. The results revealed regions related to conceptual/category processing like the right superior temporal gyrus, left precentral gyrus and middle temporal gyrus. In addition, the left middle/superior areas predicted successful learning nominal classification rules. Additionally, working memory capacity negatively correlated with activation in the bilateral thalami, suggesting a potential involvement of working memory. These findings emphasize the importance of examining typologically diverse grammatical rules and provide new insights into the neural mechanisms of rule learning.