Developmental increase in top-down and bottom-up processing in a phonological task: an effective connectivity, fMRI study

J Cogn Neurosci. 2009 Jun;21(6):1135-45. doi: 10.1162/jocn.2009.21065.

Abstract

We examined age-related changes in the interactions among brain regions in children performing rhyming judgments on visually presented words. The difficulty of the task was manipulated by including a conflict between task-relevant (phonological) information and task-irrelevant (orthographic) information. The conflicting conditions included pairs of words that rhyme despite having different spelling patterns (jazz-has), or words that do not rhyme despite having similar spelling patterns (pint-mint). These were contrasted with nonconflicting pairs that have similar orthography and phonology (dime-lime) or different orthography and phonology (press-list). Using fMRI, we examined effective connectivity among five left hemisphere regions of interest: fusiform gyrus (FG), inferior frontal gyrus (IFG), intraparietal sulcus (IPS), lateral temporal cortex (LTC), and medial frontal gyrus (MeFG). Age-related increases were observed in the influence of the IFG and FG on the LTC, but only in conflicting conditions. These results reflect a developmental increase in the convergence of bottom-up and top-down information on the LTC. In older children, top-down control process may selectively enhance the sensitivity of the LTC to bottom-up information from the FG. This may be evident especially in situations that require selective enhancement of task-relevant versus task-irrelevant information. Altogether these results provide a direct evidence for a developmental increase in top-down control processes in language processing. The developmental increase in bottom-up processing may be secondary to the enhancement of top-down processes.

MeSH terms

  • Adolescent
  • Age Factors
  • Brain / blood supply
  • Brain / physiology*
  • Brain Mapping*
  • Child
  • Child Development / physiology*
  • Female
  • Functional Laterality / physiology
  • Humans
  • Image Processing, Computer-Assisted / methods
  • Judgment / physiology
  • Magnetic Resonance Imaging / methods
  • Male
  • Oxygen / blood
  • Pattern Recognition, Visual / physiology*
  • Phonetics*
  • Photic Stimulation / methods
  • Reference Values
  • Time Factors

Substances

  • Oxygen