title: Orthographic Coding: Brain Activation for Letters, Symbols, and Digits.
abstract: The present experiment investigates the input coding mechanisms of 3 common printed characters: letters, numbers, and symbols. Despite research in this area, it is yet unclear whether the identity of these 3 elements is processed through the same or different brain pathways. In addition, some computational models propose that the position-in-string coding of these elements responds to general flexible mechanisms of the visual system that are not character-specific, whereas others suggest that the position coding of letters responds to specific processes that are different from those that guide the position-in-string assignment of other types of visual objects. Here, in an fMRI study, we manipulated character position and character identity through the transposition or substitution of 2 internal elements within strings of 4 elements. Participants were presented with 2 consecutive visual strings and asked to decide whether they were the same or different. The results showed: 1) that some brain areas responded more to letters than to numbers and vice versa, suggesting that processing may follow different brain pathways; 2) that the left parietal cortex is involved in letter identity, and critically in letter position coding, specifically contributing to the early stages of the reading process; and that 3) a stimulus-specific mechanism for letter position coding is operating during orthographic processing.
authors: Basque Center of Cognition, Brain and Language (BCBL), Donostia, Spain Ikerbasque, Basque Foundation for Science, Bilbao, Spain Department of Basque Language and Communication, University of the Basque Country EHU/UPV, Bilbao, Spain.
authors: Manuel
authors: M
authors: Carreiras
authors: Basque Center of Cognition, Brain and Language (BCBL), Donostia, Spain.
authors: Ileana
authors: I
authors: Quiñones
authors: Department of Psychobiology and Methodology, University of La Laguna, Tenerife, Spain.
authors: Juan Andrés
authors: JA
authors: Hernández-Cabrera
authors: Basque Center of Cognition, Brain and Language (BCBL), Donostia, Spain.
authors: Jon Andoni
authors: JA
authors: Duñabeitia
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005260:Female; D007839:Functional Laterality; D006236:Handwriting; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008959:Models, Neurological; D009434:Neural Pathways / Q000502:physiology; D010296:Parietal Lobe / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011932:Reading; D055815:Young Adult
keywords: Orthographic coding; fMRI; letters; numbers; symbols