Orthographic effects in spoken language: on-line activation or phonological restructuring?

Previous research has shown that literacy (i.e., learning to read and spell) affects spoken language processing. However, there is an on-going debate about the nature of this influence. Some argued that orthography is co-activated on-line whenever we hear a spoken word. Others suggested that orthography is not activated on-line but has changed the nature of the phonological representations. Finally, both effects might occur simultaneously, that is, orthography might be activated on-line in addition to having changed the nature of the phonological representations. Previous studies have not been able to tease apart these hypotheses. The present study started by replicating the finding of an orthographic consistency effect in spoken word recognition using event-related brain potentials (ERPs): words with multiple spellings (i.e., inconsistent words) differed from words with unique spellings (i.e., consistent words) as early as 330 ms after the onset of the target. We then employed standardized low resolution electromagnetic tomography (sLORETA) to determine the possible underlying cortical generators of this effect. The results showed that the orthographic consistency effect was clearly localized in a classic phonological area (left BA40). No evidence was found for activation in the posterior cortical areas coding orthographic information, such as the visual word form area in the left fusiform gyrus (BA37). This finding is consistent with the restructuring hypothesis according to which phonological representations are "contaminated" by orthographic knowledge.