An approach to separating the levels of hierarchical structure building in language and mathematics

Philos Trans R Soc Lond B Biol Sci. 2012 Jul 19;367(1598):2033-45. doi: 10.1098/rstb.2012.0095.


We aimed to dissociate two levels of hierarchical structure building in language and mathematics, namely 'first-level' (the build-up of hierarchical structure with externally given elements) and 'second-level' (the build-up of hierarchical structure with internally represented elements produced by first-level processes). Using functional magnetic resonance imaging, we investigated these processes in three domains: sentence comprehension, arithmetic calculation (using Reverse Polish notation, which gives two operands followed by an operator) and a working memory control task. All tasks required the build-up of hierarchical structures at the first- and second-level, resulting in a similar computational hierarchy across language and mathematics, as well as in a working memory control task. Using a novel method that estimates the difference in the integration cost for conditions of different trial durations, we found an anterior-to-posterior functional organization in the prefrontal cortex, according to the level of hierarchy. Common to all domains, the ventral premotor cortex (PMv) supports first-level hierarchy building, while the dorsal pars opercularis (POd) subserves second-level hierarchy building, with lower activation for language compared with the other two tasks. These results suggest that the POd and the PMv support domain-general mechanisms for hierarchical structure building, with the POd being uniquely efficient for language.

MeSH terms

  • Adult
  • Asian People
  • Comprehension
  • Computational Biology / methods
  • Executive Function
  • Female
  • Humans
  • Language*
  • Magnetic Resonance Imaging
  • Male
  • Mathematics*
  • Memory, Short-Term
  • Prefrontal Cortex / physiology*
  • Young Adult