Regional cerebral blood flow during object naming and word reading

Abstract

By several accounts, reading single words may be accomplished either by sequentially transcribing orthographic units into their corresponding sounds (an indirect route), or by directly associating a visual word form to the semantic or articulatory representation (a direct route). By contrast, the similar task of naming objects must rely only on a direct route, since objects cannot be "sounded out." To study the localization of cognitive processes specific to reading, we used positron emission tomography (PET) to measure regional cerebral blood flow while subjects named words and pictures of objects silently or aloud. Group averages of blood flow changes were obtained for experimental vs. control tasks. Object and word presentations elicited similar blood flow increases in extra-striate visual cortices compared with a visual noise control. Silent reading invoked a neural network very similar to that seen when subjects named objects silently, consistent with a "direct" route. Naming objects aloud produced the addition of motor output regions to this network. By contrast, oral reading produced a markedly different pattern of activated regions, suggesting reliance on a separate phonological pathway. These results provide support for the dual coding hypothesis in reading and challenge the use of strict hierarchical models of cognitive operations in PET activation studies.

An Event-Related fMRI Study of Overt and Covert Word Stem Completion

“…Their images for the overt condition contained significant artifact, however. Bookheimer et al (1995) used PET to compare word reading and picture naming done silently and aloud. They found similar regions of activation for picture naming across the two modes, but found differences in patterns of activation for word reading across the two modes.…”

Functional Specialization for Semantic and Phonological Processing in the Left Inferior Prefrontal Cortex

“…Viewing Words Bookheimer et al, 1995 View words Ͼ view nonsense objects Ϫ40 26 Ϫ8 Bookheimer et al, 1995 View words Ͼ view nonsense objects Ϫ36 18 4 Bookheimer et al, 1995 View words Ͼ view nonsense objects Ϫ32 14 44 Bookheimer et al, 1995 name words Ͼ view nonsense objects Ϫ32 18 8 Menard et al, 1996 View words Ͼ view X's Ϫ49 10 36 Menard et al, 1996 View words Ͼ view X's Ϫ43 20 0 32 POLDRACK ET AL.…”

The role of inferior frontal cortex in phonological processing

“…Table 1 lists the studies, tasks, and location of activation included in the analysis. In addition, based on a review by Fiez and Petersen (1998) of six studies (Bookheimer, Zeffiro, Blaxton, Gaillard, & Theodore, 1995;Fiez, unpublished data;Herbster, Mintun, Nebes, & Becker, 1997;Price, Moore, & Frackowiak, 1996a;Price et al, 1996b;Rumsey et al, 1997), the average activation and standard deviation for reading aloud tasks compared with passive or sensorimotor is included for comparison purposes. The studies are organized by modality (i.e., auditory vs. visual).…”