Using neuro-imaging to test developmental models of reading acquisition
AUTHORS
ABSTRACT
In a series of studies, Booth, Burman, Meyer, Gitelman, Parrish, and Mesulam (2002a, 2002b) developed a neurocognitive model of lexical processing using functional magnetic resonance imaging. This model suggests that auditory word forms (phonological representations) involve the superior temporal gyrus (STG), visual word forms (orthographic representations) involve the fusiform gyrus (FG), and meaning forms (amodal semantic representations) involve the middle temporal gyrus (MTG; Booth et al., 2002a, 2002b). Interactions among these representations are mediated by posterior heteromodal regions including the supramarginal (SG) and angular gyri (AG), and the inferior frontal gyrus (IFG) is involved in the online manipulation of these posterior representational systems (see Fig. 7.1 for a schematic of this neurocognitive model; FG is not shown on this lateral view, but rather is on the ventral portion of the temporal lobes). In cross-modal tasks that require the conversion of orthography to phonology (rhyming judgments to visually presented words), for example, better performance in adults is associated with greater supramarginal/angular gyrus and superior temporal gyrus activations (Booth, Burman, Meyer, Gitelman, et al., 2003). Similarly, in cross-modal tasks that require the conversion of phonology to orthography (spelling judgments to auditorily presented words), better performance is associated with greater supramarginal/angular gyrus and fusiform gyrus activa tions (Booth, Burman, Meyer, Gitelman, et al., 2003). Booth et al. (2001, 2003) demonstrated that adults show more activation than children in unimodal regions associated with the modality of lexical input (Booth, Burman, Meyer, Zhang, et al., 2003; Booth et al., 2001). However, developmental differences in the neurocognitive networks involved in crossmodal tasks have not been investigated.