Neural evidence for shared phonetic, phonological, and lexical processing of words and pseudowords

Abstract

This study uses electrocorticography (ECoG) to investigate word and pseudoword auditory processing. ECoG data are recorded from intracranial electrodes with high spatial and temporal resolution. This methodology contributes novel data to the debate over whether words and pseudowords are processed using shared streams, or whether pseudowords rely on separate sub-lexical routes. Data from left temporal lobe electrodes was recorded from two patients in a listen-and-repeat task with real words (e.g., “minority”) and pseudowords (e.g., [təmiɹɪnai]). For each electrode showing a word/pseudoword difference, regression models were fit to capture the time-varying effects of lexicality, cohort size (how many lexical items matched the current phonetic input), and cohort frequency. Preliminary results show that lexical factors had predictive power in mid- and anterior temporal electrodes. Activity peaked early in posterior electrodes and propagated forward to anterior sites. Average activity was stronger for pseudowords than words. A positive relationship was found between cohort frequency and activity; the direction of the effect varied for cohort size. Thedata is consistent with a shared streams account: along the temporal lobe, words and pseudowords share processing in acoustic, phonetic, phonological, and lexical regions, with access to stored lexical/cohort information.