Voxel‐based analysis of MRI detects abnormal visual cortex in children and adults with amblyopia

Abstract

Amblyopia, sometimes called "lazy eye," is a relatively common developmental visual disorder well characterized behaviorally; however, the neural substrates associated with amblyopia in humans remain unclear. We hypothesized that abnormalities in the cerebral cortex of subjects with amblyopia exist, possibly as a result of experience-dependent neuronal plasticity. Anatomic magnetic resonance imaging (MRI) and psychophysical vision testing was carried out on 74 subjects divided into two age ranges, 7-12 years and 18-35 years, and three diagnoses, strabismic amblyopia, anisometropic amblyopia, and normal vision. We report a behavioral impairment in contrast sensitivity for subjects with amblyopia, consistent with previous reports. When the high-resolution MRI brain images were analyzed quantitatively with optimized voxel-based morphometry, results indicated that adults and children with amblyopia have decreased gray matter volume in visual cortical regions, including the calcarine sulcus, known to contain primary visual cortex. This finding was confirmed with a separate region-of-interest analysis. For the children with amblyopia, additional gray matter reductions in parietal-occipital areas and ventral temporal cortex were detected, consistent with recent reports that amblyopia can result in spatial location and object processing deficits. These data are the first to provide possible neuroanatomic bases for the loss of binocularity and visual sensitivity in children and adults with amblyopia.

Association of Optic Radiation Integrity with Cortical Thickness in Children with Anisometropic Amblyopia

“…Decreased gray matter volume and density in different regions have been revealed by VBM [16,40], but this method does not have specificity for highly convoluted structures of the cortex [41]. SBM is a recently-developed and highly reliable MRI-derived neuroanatomical measure, which overcomes the shortcomings of volume-based analysis, and is unaffected by voxel geometry [42].…”

“…Furthermore, recent fMRI studies have shown that amblyopia is associated with deactivation in the striate cortex (Brodmann area 17), the occipitotemporal cortex, and the LGN [14,15]. In addition, the gray matter volume of the visual cortex is reduced in adults and children with amblyopia, as revealed by voxelbased morphometry (VBM) [16]. However, it has been pointed out that VBM may cause inaccurate assessment in regions of cortical overlap [17].…”

Brain Gray Matter Decrease in Chronic Pain Is the Consequence and Not the Cause of Pain

“…Given that changes in the periphery, i.e., loss of afferent input due to unilateral amputation of an extremity or phantom pain due to spinal cord injury (Wrigley et al, 2009) and even amblyopia (Mendola et al, 2005) and strabismus (Chan et al, 2004) may change the brain structure of individuals, one has to conclude that these changes are possibly a result of experience-dependent neuronal plasticity (Draganski and May, 2008). Our data provide evidence for activation-dependant brain plasticity in humans on a structural level (Draganski et al, 2004;Boyke et al, 2008) as the key to structural changes of the brain in chronic pain patients.…”

Amblyopia and Real-World Visuomotor Tasks

“…Following Fielder's (2002) remarks, there is now convincing evidence of abnormalities in structure and function within the vision-for-perception and vision-foraction cortex of people with amblyopia (Lerner et al, 2003;Mendola et al, 2005;Anderson & Swettenham, 2006;Muckli et al, 2006;Yan et al, 2010) and for less effective communication between the two streams (Li et al, 2011). It should, therefore, come as little surprise that amblopes exhibit a range of visuomotor impairments, especially when using their affected eye (e.g., Grant et al, 2007) when its visual acuity (VA) loss is 'moderate' (e.g., logMAR 0.5-1.0) or 'severe' (e.g., logMAR >1.0).…”