Decoding the Neuroanatomical Basis of Reading Ability: A Multivoxel Morphometric Study

Abstract

As a relatively recent cultural invention in human evolution, reading is an important gateway to personal development and socioeconomic success. Despite the well documented individual differences in reading ability, its neuroanatomical correlates have not been well understood, largely due to the fact that reading is a complex skill that consists of multiple components. Using a large sample of 416 college students and 7 reading tasks, the present study successfully identified three uncorrelated components of reading ability: phonological decoding, form-sound association, and naming speed. We then tried to predict individuals' scores in these components from their gray matter volume (GMV) on a subset of participants (N ϭ 253) with high-quality structural images, adopting a multivariate support vector regression analysis with tenfold cross-validation. Our results revealed distinct neural regions that supported different aspects of reading ability: whereas phonological decoding was associated with the GMV in the left superior parietal lobe extending to the supramarginal gyrus, form-sound association was predicted by the GMV in the hippocampus and cerebellum. Naming speed was associated with GMV in distributed brain regions in the occipital, temporal, parietal, and frontal cortices. Phonological decoding and form-sound association were uncorrelated with general cognitive abilities. However, naming speed was correlated with intelligence and processing speed, and some of the regions that were predictive of naming speed also predicted these general cognitive abilities. These results provide further insights on the cognitive and neural architecture of reading and the structural basis of individual differences in reading abilities.

The Association between Gray Matter Volume and Reading Proficiency: A Longitudinal Study of Beginning Readers

“…Whereas better readers on average exhibited volume reductions, poor readers on average exhibited volume growth in these areas. These findings seem inconsistent with previous findings of positive correlations between measures of cortical volume and reading proficiency in left inferior parietal regions, as reported by some of the studies cited above (i.e., He et al, 2013;Blackmon et al, 2010). Furthermore, the only previous study that reports volume changes directly related to reading acquisition found higher gray matter density in temporoparietal regions in persons who acquired literacy as adults when compared with illiterate adults (Carreiras et al, 2009).…”

“…In contrast to these studies, no association between gray matter volume at baseline or follow-up measurement and reading proficiency at the respective (or the following) measurement time point could be found in this study. However, intraindividual changes in reading proficiency between the two measurement time points were positively related to baseline gray matter volume in the superior temporal gyrus, including parts of the planum temporale, that is, similar areas as reported by some of the studies cited above (i.e., He et al, 2013;Blackmon et al, 2010;Steinbrink et al, 2008). Furthermore, it resonates with studies reporting neurostructural differences between normal reading participants and participants suffering from developmental dyslexia, a specific impairment affecting the acquisition of reading skills.…”

“…Previous studies that related reading performance to measures of gray matter volume, gray matter density, or gray matter thickness in normal reading participants in a cross-sectional manner, that is, at only one point in time, reported mostly positive associations in temporoparietal (He et al, 2013;Blackmon et al, 2010;Steinbrink et al, 2008) and occipitotemporal regions (Zhang et al, 2013;Hoeft et al, 2007). In contrast to these studies, no association between gray matter volume at baseline or follow-up measurement and reading proficiency at the respective (or the following) measurement time point could be found in this study.…”

“…More specifically, a positive association between reading performance and measures of gray matter volume, density, or thickness has been demonstrated in bilateral (Blackmon et al, 2010) or left (He et al, 2013;Steinbrink et al, 2008) temporoparietal and left (Zhang et al, 2013) or right (Hoeft et al, 2007) occipitotemporal regions. In addition, negative correlations have been reported for left occipitotemporal and bilateral inferior frontal regions (Blackmon et al, 2010) and the left posterior cingulate cortex (He et al, 2013). Furthermore, as all of these studies employed a cross-sectional design (i.e., participants were studied at only one point in time), they cannot answer the question of whether reading-related differences in cortical anatomy arise in the course of reading instruction and represent the result of different levels of reading proficiency or whether they can be regarded as a preexisting condition possibly causing differences in reading proficiency.…”

Coherence: The Measurement and Application of Brain Connectivity

“…Although neuropsychological studies such as Broca's have been valuable, technological advances in neuroimaging have drastically expanded the types of questions we can ask about cognition, especially in the healthy brain. For example, neuroimaging techniques have uncovered and refined theories about brain areas being "dedicated" to some domains of cognition, such as face processing (Kanwisher, McDermott, & Chun, 1997), phonological decoding (Boukrina, Barrett, Alexander, Yao, & Graves, 2015;He at al., 2013,), and the planning of motor speech (Dronkers, 1996;Richardson, Fillmore, Rorden, LaPointe, & Fridriksson, 2012).…”