Altered White Matter Integrity in the Congenital and Late Blind People

Dawei Wang,Tianzi Jiang,Chunshui Yu,Wen Qin,Yong Liu,Yunting Zhang

doi:10.1155/2013/128236

Abstract

The blind subjects have experienced a series of brain structural and functional alterations due to the visual deprivation. It remains unclear as to whether white matter changes differ between blind subjects with visual deprivation before and after a critical developmental period. The present study offered a direct comparison in changes of white matter fractional anisotropy (FA) between congenital blind (CB) and late blind (LB) individuals. Twenty CB, 21 LB (blindness onset after 18 years old), and 40 sight control (SC) subjects were recruited. Both the tract-based spatial statistics (TBSS) and voxel-based analysis (VBA) showed lower FA in the bilateral optic radiations in both blind groups, suggesting that the loss of white matter integrity was the prominent hallmark in the blind people. The LB group showed more extensive white matter impairment than the CB group, indicating the mechanisms of white matter FA changes are different between the CB and LB groups. Using a loose threshold, a trend of an increased FA was found in the bilateral corticospinal tracts in the LB but with a smaller spatial extent relative to the CB. These results suggest that white matter FA changes in the blind subjects are the reflection of multiple mechanisms, including the axonal degeneration, deafferentation, and plasticity.

Highlights

The blind subjects, irrespective of the age of onset, have experienced a series of structural and functional alterations, and they have to make major adjustments to interact effectively with the environment
We investigated if the reduced fractional anisotropy (FA) in optic radiation (OR) in the congenitally blind (CB) is correlated with the chronological age that is equal to the duration of blindness in the CB subjects
No significant group difference was found in gender (χ2 = 2.70, P = 0.26), subtle difference existed in ratio of males/total subjects among the three groups (0.65 in CB; 0.76 in late blind (LB); and 0.55 in sight control (SC))

Summary

Introduction

The blind subjects, irrespective of the age of onset, have experienced a series of structural and functional alterations, and they have to make major adjustments to interact effectively with the environment. Structural MRI studies have shown the decreased gray/white matter volume [12,13,14] but increased cortical thickness in the occipital cortex [15, 16]. Different DTI analytic methods have shown that congenitally blind (CB) or early blind (EB) subjects had atrophy [20] or decreased white matter integrity [21] in the optic radiation (OR), reduced efficiency of the brain anatomical network [22], and increased white matter integrity in the corticospinal tract (CST) [23]. No significant decreased white matter integrity in the ORs has been reported in a voxel-based analysis (VBA) in a group of six LB individuals [24] and in a diffusion tensor tractography (DTT) based analysis in LB subjects [25]. Significant atrophy was found in the visual cortices in both the LB and EB subjects [13]

Methods

Discussion

Conclusion