fMRI Evidence for ACV98 Connectionist Model for Reading of Mono and Multi-Syllabic Words and Pseudo-Words

Abstract

According to predictions made by ACV98 connectionist model of reading, behavioral experiments have shown that syllabic length affects naming latencies for pseudo-words but not for words. ACV98 postulates the existence of two successive reading procedures. According to it, any orthographical object (word or pseudo-word) is first submitted to a global processing which aims to find a “lexical familiarity” computed from previously experienced words. If it is found, the corresponding phonological form of the stimulus is activated and reading is performed. If it is not found, a subsequent analytical processing is performed within the input stimulus using the same route, in order to extract familiar orthographic components (typically, syllables) as well as their corresponding phonological forms. The syllabic phonological forms are successively and temporarily maintained in a phonological buffer, before being assembled into a whole phonological form. Overall, this model predicts that words are read by using the global procedure, while the pseudo-words are read by using the analytical procedure. The present event-related fMRI study aimed to assess the effect of syllabic length on cerebral activity during reading, in order to obtain additional anatomo-functional information as support to this model as well as to behavioral results. Based on ACV98 predictions and in terms of cerebral network, we hypothesized (1) a lexicality effect: there should be no differences between words and pseudo-words, they are processed within a common network of cerebral regions, and (2) a syllable length effect: the length influences cerebral activity only during pseudo-words reading because only long pseudo-words are processed following an analytical procedure involving supplementary visual analysis, visuo-spatial attention and working memory processes. Eight right-handed volunteers performed a silent reading task on French printed words and pseudo-words. A pseudo-randomized event-related paradigm with 6 types (words=W and pseudo-words=PW composed of 1, 2 and 3 syllables) of stimuli was used. Data processing was performed using SPM'99. Our results have shown that (1) Words and pseudo-words involved common mechanisms such as visuo-orthographic, phonological, attentional and motor processes. No process was significantly more involved for one or the other of two types of stimuli (word or pseudo-word). This result is a priori more in agreement with “single way models” and particularly with ACV'98 than with dual-route models. Nonetheless the dual-route model cannot be excluded; (2) A length effect on cerebral activity was obtained only during pseudo-word reading suggesting an analytical procedure involvement during reading of long pseudo-words, as ACV'98 predicts