Developmental increase in top-down and bottom-up processing in a phonological task: an effective connectivity, fMRI study.
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.
Bitan
Tali
T
Department of Communication Disorders, Haifa University, Mount Carmel, Haifa, Israel. tbitan@research.haifa.ac.il
Cheon
Jimmy
J
Lu
Dong
D
Burman
Douglas D
DD
Booth
James R
JR
D000293:Adolescent; D000367:Age Factors; D001921:Brain / Q000098:blood supply / Q000502:physiology*; D001931:Brain Mapping; D002648:Child; D002657:Child Development / Q000502:physiology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007600:Judgment / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D010100:Oxygen / Q000097:blood; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010700:Phonetics; D010775:Photic Stimulation / Q000379:methods; D012016:Reference Values; D013997:Time Factors
D010100:Oxygen