title: A dynamic causal modeling analysis of the effective connectivities underlying top-down letter processing.
abstract: The present study employed dynamic causal modeling to investigate the effective functional connectivity between regions of the neural network involved in top-down letter processing. We used an illusory letter detection paradigm in which participants detected letters while viewing pure noise images. When participants detected letters, the response of the right middle occipital gyrus (MOG) in the visual cortex was enhanced by increased feed-backward connectivity from the left inferior frontal gyrus (IFG). In addition, illusory letter detection increased feed-forward connectivity from the right MOG to the left inferior parietal lobules. Originating in the left IFG, this top-down letter processing network may facilitate the detection of letters by activating letter processing areas within the visual cortex. This activation in turns may highlight the visual features of letters and send letter information to activate the associated phonological representations in the identified parietal region.
authors.affiliation: Department of Biomedical Engineering, School of Computer and Information Technology, Beijing Jiaotong University, Beijing 100044, China.
authors.forename: Jiangang
authors.initials: J
authors.lastname: Liu
authors.affiliation: School of Life Sciences and Technology, Xidian University, Xi'an 710071, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.affiliation: University of California, San Diego, CA, USA.
authors.forename: Cory A
authors.initials: CA
authors.lastname: Rieth
authors.affiliation: University of California, San Diego, CA, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Huber
authors.affiliation: School of Life Sciences and Technology, Xidian University, Xi'an 710071, China; Institute of Automation, Chinese Academy of Sciences, P.O. Box 2728, Beijing 100190, China. Electronic address: tian@ieee.org.
authors.forename: Jie
authors.initials: J
authors.lastname: Tian
authors.affiliation: University of California, San Diego, CA, USA; University of Toronto, Canada. Electronic address: kang.lee@utoronto.ca.
authors.forename: Kang
authors.initials: K
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply / Q000502:physiology*; D004192:Discrimination, Psychological; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008959:Models, Neurological; D009434:Neural Pathways / Q000098:blood supply / Q000502:physiology*; D017711:Nonlinear Dynamics; D010100:Oxygen / Q000097:blood; D010775:Photic Stimulation / Q000379:methods; D014825:Vocabulary; D055815:Young Adult
chemical_list: D010100:Oxygen