Some neurophysiological constraints on models of word naming

Abstract

The pronunciation of irregular words in deep orthographies like English cannot be specified by simple rules. On the other hand, the fact that novel letter strings can be pronounced seems to imply the existence of such rules. These facts motivate dual-route models of word naming, which postulate separate lexical (whole-word) and non-lexical (rulebased) mechanisms for accessing phonology. We used fMRI during oral naming of irregular words, regular words, and nonwords, to test this theory against a competing single-mechanism account known as the triangle model, which proposes that all words are handled by a single system containing distributed orthographic, phonological, and semantic codes rather than word codes. Two versions of the dual-route model were distinguished: an dexclusiveT version in which activation of one processing route predominates over the other, and a dparallelT version in which both routes are equally activated by all words. The fMRI results provide no support for the exclusive dual-route model. Several frontal, insular, anterior cingulate, and parietal regions showed responses that increased with naming difficulty (nonword > irregular word > regular word) and were correlated with response time, but there was no activation consistent with the predicted response of a nonlexical, rule-based mechanism (i.e., nonword > regular word > irregular word). Several regions, including the angular gyrus and dorsal prefrontal cortex bilaterally, left ventromedial temporal lobe, and posterior cingulate gyrus, were activated more by words than nonwords, but these dlexical routeT regions were equally active for irregular and regular words. The results are compatible with both the parallel dual-route model and the triangle model. dLexical routeT regions also showed effects of word imageability. Together with previous imaging studies using semantic task contrasts, the imageability effects are consistent with semantic processing in these brain regions, suggesting that word naming is partly semantically-mediated. D 2005 Elsevier Inc. All rights reserved. Keywords: Word naming; Dual-route model; Triangle model IntroductionThe correspondence between spoken and written forms of a language is not always systematic. While in some alphabetic orthographies the sound of a word can be worked out using rules of pronunciation, in most, there are varying degrees of irregularity in the mapping between print and sound. In English, for example, Bernard Shaw pointed out that the word ''fish'' could be written ghoti if one were mischievous enough to borrow the spelling for /f/ from rough, the spelling of /I/ from women, and the spelling of /sh/ from nation. Words like colonel and yacht are only some of the more extreme examples of such irregularity of pronunciation, which is pervasive in English and is seen in many of its more common words, including some, many, of, the, and word just used in this sentence.While the pronunciation of these dirregularT words would seem to be learned through rote memorization of the whole word, there is...

Attentional and linguistic interactions in speech perception

“…The three regions that showed lexical (word > pseudoword) responses only in the Attend condition are among those frequently identified in imaging studies of semantic processing (e.g., Binder et al, 1999;Binder et al, 2003;Binder et al, 2005;Demonet et al, 1992;Mummery et al, 1998;Price et al, 1997;Roskies et al, 2001;Scott et al, 2003;Spitsyna et al, 2006). Other areas often identified in these studies include the anterior and ventral temporal lobes (particularly the fusiform and parahippocampal gyri), angular gyrus, and posterior cingulate gyrus.…”

Tuning of the human left fusiform gyrus to sublexical orthographic structure

“…Thus, this region may participate in the recognition of many or even most visual inputs and yet also display perceptual expertise for letter strings. Several authors have reported stronger activation in this general region (and surrounding extrastriate cortex) for reading word-like pseudowords compared to words (Binder et al, 2005a;Kronbichler et al, 2004;Mechelli et al, 2003;Price et al, 1996;Xu et al, 2001). It seems very likely that this difference is related to the longer processing time and visual attention required for reading pseudowords, as the same region showed activation correlated with RT during overt word and pseudoword naming (peak at −42, −55, −10) (Binder et al, 2005a) and during a visual lexical decision task (peak at −42, −52, −17) (Binder et al, 2005b) and was activated by covert shifts of visual attention in an experiment using meaningless geometric shapes to cue the spatial location of targets (peak at −45, −69, −6) (Gitelman et al, 1999).…”

Neural substrates of phonological and lexicosemantic representations in Alzheimer's disease

“…Then, small volume correction (SVC) was applied (using P 0.05, corrected) on published coordinates for a priori brain regions considered to be involved in either phonological or lexicosemantic processing. For lexicosemantic knowledge, a 10-mm radius spherical volume was used centered on [(255, 14, 221); Majerus et al, 2002] for the anterior superior temporal sulcus, [(254, 248, 26), Davis, 2004] for the posterior middle temporal gyrus, [(261, 222, 217), Majerus et al, 2002] for the inferior temporal gyrus, [(247, 283, 25), Binder et al, 2005] for the inferior parietal lobule (angular gyrus), and [(245, 35, 24), Binder et al, 1996] for the inferior frontal gyrus [Binder, 2000;Binder et al, 1996Binder et al, , 1999Binder et al, , 2005Demonet et al, 1992Demonet et al, , 1994Howard et al, 1992;Majerus et al, 2002;Perani et al, 1996;Petersen et al, 1988;Price et al, 1996;Scott et al, 2000]. Similarly, a priori regions of interest for phonological levels of representation were based on previous studies of sublexical phonological processing of speech: SVC was centered on [(260, 24, 210) and (66, 212, 0), Scott et al, 2000] for the bilateral superior temporal sulci and [(253, 243, 6) and (56 230 4), Binder et al, 2000] for the bilateral posterior superior temporal gyri [Binder, 2000;Binder and Price, 2001;Binder et al, 2000;Burton et al, 2000Burton et al, , 2005Demonet et al, 1992Demonet et al, , 1994Hickok and Poeppel, 2000;Jacquemot et al, 2003;<...>…”