When does the brain register deviances from standard word spellings?--An ERP study.

Event-related potentials (ERPs) in response to the standard form of words (e.g., taxi) were compared with ERPs in response to letter-altered (e.g., taksi) or case-altered forms (e.g., taXi). The altered forms always resulted in the same reading as the standard forms. First divergences between ERPs were found at around 160 ms. At occipital sites, the peak amplitude of the N160 was higher for standard than letter-altered strings. At frontal and central sites, the standard strings diverged from the altered strings persistently by higher positivity from about 160 ms onwards. These early ERP differences between standard and altered visual word forms speak for early contact between the letter input and stored visual-orthographic representations of words.