, 2000). The VWFA is the primary candidate neural site for the long-hypothesized visual word lexicon (Dejerine, 1892, Warrington and Shallice, 1980 and Wernicke, 1874), although debates about its specific role continue (Dehaene and Cohen, Sorafenib purchase 2011, Price and Devlin, 2011 and Wandell et al., 2010). Ultimately, the VWFA is thought to communicate directly with language-related regions (Devlin et al., 2006). These language cortices presumably require a common input format that is insensitive to particular visual features. The VWFA may act as an essential link between visual and language cortices by providing such a common input format (Jobard et al., 2003). Alternatively, the
collection of visual areas may have separate access to the same network with the potential to bypass the VWFA (Price and Devlin, 2011 and Richardson et al., 2011). We took a fresh look at this question by measuring responses to word stimuli intended to target different feature-specialized visual cortical regions (Figure 1). Specifically, http://www.selleckchem.com/products/ink128.html we designed word stimuli
whose shape is defined using atypical features: dots rather than line contours. The dots carried word information by spatially varying dot luminance, dot motion direction, or both. Current hypotheses suggest that the VWFA, through reading experience, becomes specialized for detecting particular line contour configurations (Dehaene and Cohen, 2011, Szwed FAK et al., 2009 and Szwed et al., 2011). Thus, the VWFA may not be expected to respond to dot-defined word stimuli that contain no line contours. Motion-defined words, for example, are expected to be processed by a motion-specialized cortical region (hMT+) located in the canonical
dorsal visual pathway (Ungerleider and Mishkin, 1982) and may not depend on the VWFA in the ventral visual pathway. Previous literature suggests an important role for the human motion complex (hMT+) in reading. Following the description of behavioral and anatomical motion processing deficits in dyslexia (Galaburda and Livingstone, 1993, Livingstone et al., 1991 and Martin and Lovegrove, 1987), hMT+ was found to be underactivated in dyslexics in response to motion stimuli when measured using functional magnetic resonance imaging (fMRI) (Eden et al., 1996). Further studies revealed that the extent of hMT+ response to visual motion correlates with reading ability more generally (Ben-Shachar et al., 2007a, Demb et al., 1997 and Demb et al., 1998). Based on these results, one might speculate that hMT+ serves a crucial role in reading. However, the nature of that role and its relationship to the VWFA have not been elucidated. By measuring (using fMRI) and disrupting (using transcranial magnetic stimulation, TMS) neural activity in hMT+, we tested its causal role in seeing words.