Origins of the specialization for letters and numbers in ventral occipitotemporal cortex

• Published in: Trends in cognitive sciences Vol. 19; no. 7; pp. 374 - 382
• Main Authors: Hannagan, Thomas, Amedi, Amir, Cohen, Laurent, Dehaene-Lambertz, Ghislaine, Dehaene, Stanislas
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2015
• Subjects: Animals; Brain Mapping; Concept Formation - physiology; cortical topology; Humans; invariance; Mathematics; metamodal areas; Nerve Net - physiology; Neurology; NFA; Occipital Lobe - physiology; Psychiatry; Reading; Recognition (Psychology) - physiology; structural connectivity; Temporal Lobe - physiology; VWFA; NFA; structural connectivity; invariance; VWFA; cortical topology; metamodal areas
• ISSN: 1364-6613; 1879-307X
• DOI: 10.1016/j.tics.2015.05.006

•The VWFA and NFA are areas specializing in letter and number recognition, respectively.•The locations of these symbol form areas are conserved in blind participants.•Their existence cannot be explained by evolutionary changes or visual constraints.•Symbol form areas may emerge from connectivity biases and/or shape feature preferences. Deep in the occipitotemporal cortex lie two functional regions, the visual word form area (VWFA) and the number form area (NFA), which are thought to play a special role in letter and number recognition, respectively. We review recent progress made in characterizing the origins of these symbol form areas in children or adults, sighted or blind subjects, and humans or monkeys. We propose two non-mutually-exclusive hypotheses on the origins of the VWFA and NFA: the presence of a connectivity bias, and a sensitivity to shape features. We assess the explanatory power of these hypotheses, describe their consequences, and offer several experimental tests.