Altering Cortical Connectivity: Remediation-Induced Changes in the White Matter of Poor Readers

Timothy A Keller,Marcel Adam Just

doi:10.1016/j.neuron.2009.10.018

Timothy A Keller, Marcel Adam Just

Open Access

https://doi.org/10.1016/j.neuron.2009.10.018

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Journal: Neuron	Publication Date: Dec 1, 2009
Citations: 375	License type: publisher-specific-oa

Affiliation: Carnegie Mellon University

Abstract

Neuroimaging studies using diffusion tensor imaging (DTI) have revealed regions of cerebral white matter with decreased microstructural organization (lowerfractional anisotropy or FA) among poor readers. We examined whether 100 hr of intensive remedial instruction affected the white matter of 8- to 10-year-old poor readers. Prior to instruction, poor readers had significantly lower FA than good readers in a region of the left anterior centrum semiovale. The instruction resulted in a change in white matter (significantly increased FA), and in the very same region. The FA increase was correlated with a decrease in radial diffusivity (but not with a change in axial diffusivity), suggesting that myelination had increased. Furthermore, the FA increase was correlated with improvement in phonological decoding ability, clarifying the cognitive locus of the effect. The results demonstrate the capability of a behavioral intervention to bring about a positive change in cortico-cortical white matter tracts.

Highlights

A major challenge of cognitive neuroscience is to understand how changes in the structural properties of the brain underpin the plasticity exhibited whenever a person develops, ages, learns a new skill, or adapts to a neuropathology
fractional anisotropy (FA) may be reduced in poor readers due to a number of possible differences in the microstructural properties of white matter, including reduced myelination, reduced axonal packing density, decreased axonal diameter, or reduced coherence of the orientation of axons within the region (Beaulieu, 2002; Ben-Shachar et al, 2007), all of which might impact the efficiency of communication among cortical areas
The remedial instruction was distributed over about 6 months of schooling, with instruction occurring in groups of three children with one teacher

Summary

Introduction

A major challenge of cognitive neuroscience is to understand how changes in the structural properties of the brain underpin the plasticity exhibited whenever a person develops, ages, learns a new skill, or adapts to a neuropathology. Reading difficulty has been associated with lower functional connectivity (the synchronization of neural activity) across areas of the reading cortical network (Hampson et al, 2006; Horwitz et al, 1998; Pugh et al, 2000) This suggests that reading disability might be associated with structural properties of the white matter that provides the anatomical connectivity among the individual nodes of the reading network. Consistent with this view, several DTI studies of poor readers have found white matter regions with lower FA compared with controls (Beaulieu et al, 2005; Deutsch et al, 2005; Klingberg et al, 2000; Niogi and McCandliss, 2006; Odegard et al, 2009; Richards et al, 2008; Rollins et al, 2009). FA may be reduced in poor readers due to a number of possible differences in the microstructural properties of white matter, including reduced myelination, reduced axonal packing density, decreased axonal diameter, or reduced coherence of the orientation of axons within the region (Beaulieu, 2002; Ben-Shachar et al, 2007), all of which might impact the efficiency of communication (bandwidth) among cortical areas

Results

Discussion

Conclusion