Interindividual uniformity and variety of the “Writing center”: A functional MRI study

Abstract

Our aim is to investigate the neural substrates for writing using fMRI (twenty right-handed subjects). We assumed that common areas involved in both writing with right and left hands are crucial to the central process of writing. We employed Japanese phonograms (Kana), in which phoneme-grapheme conversion would be extremely simple. Brain activation was examined under three conditions: (1) written naming with the right hand (WR), (2) written naming with the left hand (WL), and (3) naming silently (NA). While the comparison of WR to NA (WR>NA) exhibited activation only in the left frontoparietal area, the WL>NA comparison exhibited broader activation than the WR>NA comparison, i.e., the left frontoparietal area except the motor and sensory areas and the right frontoparietal area. A conjunction analysis in SPM2 revealed common areas of activation across the WR>NA and WL>NA comparisons, which are assumed to be crucial to writing. In the group analysis, three areas were found to be activated: the posterior end of the left superior frontal gyrus, which is superior and posterior to Exner's center; the anterior part of the left superior parietal lobule; and the lower part of the anterior limb of the left supramarginal gyrus. In the single-subject analysis, whereas the first two of the above three areas were found to be crucial for writing in all individuals, an interindividual inconsistency of involvement with writing was observed in three areas: the lower part of the anterior limb of the left supramarginal gyrus (60% involved); the right frontal region (47%); and the right intraparietal sulcus (47%).

Developmental increases in effective connectivity to brain regions involved in phonological processing during tasks with orthographic demands

“…For both modalities, there were modulatory effects involving inferior frontal gyrus, inferior parietal cortex and fusiform gyrus. This is broadly consistent with studies in adults that have reported activation in these regions in a variety of spelling tasks (Beeson et al, 2003;Booth et al, 2002;Katanoda et al, 2001;Menon and Desmond, 2001;Nakamura et al, 2000;Petrides et al, 1995;Sugihara et al, 2006;Sugishita et al, 1996;Tokunaga et al, 1999). None of these studies, however, found activation in superior temporal gyrus, whereas our study revealed reliable activation in and modulatory effects on connections with superior temporal gyrus in both visual and auditory modalities.…”

“…None of these studies, however, found activation in superior temporal gyrus, whereas our study revealed reliable activation in and modulatory effects on connections with superior temporal gyrus in both visual and auditory modalities. This could be explained by task differences as most of previous studies used physical writing which may have placed greater emphasis on motor processes (Beeson et al, 2003;Katanoda et al, 2001;Menon and Desmond, 2001;Nakamura et al, 2000;Petrides et al, 1995;Sugihara et al, 2006;Tokunaga et al, 1999). In contrast, our tasks involved spelling judgments to sequentially presented words, so it is more likely that phonological processes were engaged.…”

“…These studies have used a variety of tasks including mentally writing the written word form (Sugishita et al, 1996), converting Japanese Kana words to Kanji characters and then mentally recalling their visual form (Nakamura et al, 2000), spelling judgments independent of whether words are presented in the auditory or visual modality as compared to rhyming judgments (Booth et al, 2002), physical writing of a visually presented word (Nakamura et al, 2000), physical writing of a spoken word (Menon and Desmond, 2001;Petrideset al, 1995;Tokunaga et al, 1999), physical writing of associates of a semantic category (Beeson et al, 2003), and physical writing of a word referring to a visual picture (Katanoda et al, 2001;Sugihara et al, 2006). The most consistent finding across these spelling studies in adults is activation in left inferior parietal cortex, a region that has been implicated in mapping between phonological and orthographic representations (Booth et al, 2002(Booth et al, , 2003a.…”

Association of dorsal inferior frontooccipital fasciculus fibers in the deep parietal lobe with both reading and writing processes: a brain mapping study

“…2,28 Previous functional studies using fMRI have identified several writing-related areas, including the superior parietal lobule, the supramarginal gyrus of the inferior parietal lobule, and the intraparietal sulcus. 19,25,43 However, little is known about how these cortical regions interact with other cortical or subcortical sites and what the most crucial white matter tracts are in relation to the writing process.…”

Dynamic Bayesian network modeling of fMRI: A comparison of group-analysis methods

“…Many studies have found that fMRI activation patterns may considerably differ among subjects even within the same group. For example, Sugihara et al (2006) found three of the five regions related to writing were inconsistently activated among subjects; in Vandenbroucke et al (2004)'s study, eighteen of twenty nine subjects showed activation varied in both location and size. These results suggest that the similarity and diversity among group members should be balanced in group models, rather than either over-emphasized or neglected.…”