Berlin School of Mind and Brain, Humboldt Universität zu Berlin, Berlin, Germany.
Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
Brain Struct Funct. 2020 Sep;225(7):1997-2015. doi: 10.1007/s00429-020-02105-7. Epub 2020 Jun 26.
The ability to generate complex hierarchical structures is a crucial component of human cognition which can be expressed in the musical domain in the form of hierarchical melodic relations. The neural underpinnings of this ability have been investigated by comparing the perception of well-formed melodies with unexpected sequences of tones. However, these contrasts do not target specifically the representation of rules generating hierarchical structure. Here, we present a novel paradigm in which identical melodic sequences are generated in four steps, according to three different rules: The Recursive rule, generating new hierarchical levels at each step; The Iterative rule, adding tones within a fixed hierarchical level without generating new levels; and a control rule that simply repeats the third step. Using fMRI, we compared brain activity across these rules when participants are imagining the fourth step after listening to the third (generation phase), and when participants listened to a fourth step (test sound phase), either well-formed or a violation. We found that, in comparison with Repetition and Iteration, imagining the fourth step using the Recursive rule activated the superior temporal gyrus (STG). During the test sound phase, we found fronto-temporo-parietal activity and hippocampal de-activation when processing violations, but no differences between rules. STG activation during the generation phase suggests that generating new hierarchical levels from previous steps might rely on retrieving appropriate melodic hierarchy schemas. Previous findings highlighting the role of hippocampus and inferior frontal gyrus may reflect processing of unexpected melodic sequences, rather than hierarchy generation per se.
生成复杂层次结构的能力是人类认知的一个关键组成部分，它可以在音乐领域以层次旋律关系的形式表现出来。为了研究这种能力的神经基础，研究人员比较了对优美旋律和出人意料的音调序列的感知。然而，这些对比并不能专门针对生成层次结构的规则表示。在这里，我们提出了一种新的范式，在这个范式中，相同的旋律序列按照三个不同的规则分四步生成：递归规则，每一步生成新的层次结构；迭代规则，在固定的层次结构内添加音高，而不生成新的层次结构；控制规则，只是重复第三步。使用 fMRI，我们比较了参与者在听到第三步（生成阶段）后想象第四步（想象阶段），以及参与者在听到第四步（测试声音阶段）时的大脑活动，无论第四步是优美的还是违反规则的。与重复和迭代相比，我们发现，在想象第四步时使用递归规则会激活上颞叶（STG）。在测试声音阶段，我们发现处理违反规则时额颞顶叶活动和海马体去激活，但规则之间没有差异。在生成阶段 STG 的激活表明，从先前的步骤生成新的层次结构可能依赖于检索适当的旋律层次结构模式。先前的发现强调了海马体和下额叶回的作用，可能反映了对出人意料的旋律序列的处理，而不是层次结构的生成本身。
