Uncovering phonological and orthographic selectivity across the reading network using fMRI-RA

Abstract

Reading has been shown to rely on a dorsal brain circuit involving the temporoparietal cortex (TPC) for grapheme-to-phoneme conversion of novel words (Pugh et al., 2001), and a ventral stream involving left occipitotemporal cortex (OTC) (in particular in the so-called “visual word form area”, VWFA) for visual identification of familiar words. In addition, portions of the inferior frontal cortex (IFC) have been posited to be an output of the dorsal reading pathway involved in phonology. While this dorsal versus ventral dichotomy for phonological and orthographic processing of words is widely accepted, it is not known if these brain areas are actually strictly sensitive to orthographic or phonological information. Using an fMRI rapid adaptation technique we probed the selectivity of the TPC, OTC, and IFC to orthographic and phonological features during single word reading. We found in two independent experiments using different task conditions in adult normal readers, that the TPC is exclusively sensitive to phonology and the VWFA in the OTC is exclusively sensitive to orthography. The dorsal IFC (BA 44), however, showed orthographic but not phonological selectivity. These results support the theory that reading involves a specific phonological-based temporoparietal region and a specific orthographic-based ventral occipitotemporal region. The dorsal IFC, however, was not sensitive to phonological processing, suggesting a more complex role for this region.

Evidence for rapid localist plasticity in the ventral visual stream: the example of words

“…We have shown previously that the VWFA holds a finely tuned orthographic representation that is not modulated by semantics or phonology (Glezer et al, 2009; Glezer et al, 2016), supporting the DRC model of reading (Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001; Coltheart & Rastle, 1994) and other models that posit whole word lexical representations in which orthographic forms are stored as distinct units. In contrast, our results provide less support for models of reading such as the Triangle model (Seidenberg & McClelland, 1989) that have argued against the existence of an orthographic lexicon.…”

A Confluence of Complexity: Intersections Among Reading Theory, Neuroscience, and Observations of Young Readers

“…Their prior experience with print supports increased brain activation (Sela, Izzetoglu, Izzetoglu, & Onaral, 2014). Thus, readers draw on prior print experiences for orthographic processing, involving the visual representation of words or groups of letters (Dehaene & Cohen, 2011; Fischer‐Baum, Bruggemann, Gallego, Li, & Tamez, 2017) to support rapid identification of familiar words without phonological processing (Glezer et al, 2016), facilitating fluent reading and comprehension.…”

Brain structures associated with reading and their abnormalities in dyslexia: a whole-brain analysis

“…We found no significant correlations between phonological scores and neuroanatomical findings. A potential reason for this might be that only relatively small brain areas, suggested to be restricted to the left temporal and angular gyri (Glezer et al, 2016) process phonology and that the present analyses controlling for various nuisance variables impede small effects to become significant. Moreover, while both groups had more than 20 subjects, our overall sample size remained moderate, which in turn decreases power to observe small effects in the data.…”