ERPs reveal early feedforward orthographic and phonological selectivity during single word reading.
Laurie S. Glezer1, Katherine J. Midgely1, Karen Emmorey1, Phillip J. Holcomb1; 1San Diego State University
Previous fMRI research indicates that in the ventral visual processing stream there is a region in the fusiform gyrus that contains neurons that are tuned to the written form of real words and in the dorsal processing stream there is a region in the temporoparietal area that contains neurons tuned to the phonology of real written words. However, due to the poor temporal resolution of fMRI, it is unclear whether this selectivity is generated in a feedforward fashion or is a result of top-down feedback. The Bimodal Interactive Activation Model (Grainger and Holcomb, 2009) is based on findings from behavioral and ERP research using priming paradigms. This model supports the idea that single word reading is accomplished in a mostly hierarchical, feedforward fashion and that orthographic and phonological whole word recognition is achieved by 325 ms. However, much of the evidence to support this is based on nonword to real word priming paradigms. In the current ERP study, we presented real words in both the prime and target position and systematically altered the orthographic and phonological similarity examining precisely when selectivity to orthographic and phonological representations occurs for single word reading. Our results show orthographic and phonological selectivity can occur earlier than previously suggested and that this selectivity is achieved within the N250 window in posterior sites for orthography and anterior sites for phonology. These results suggest that the whole word selectivity reported in fMRI studies is likely the result of the initial feedforward pass and not top-down feedback.
Topic Area: LANGUAGE: Other