The Effect of Blindness on Spatial Asymmetries

Area of Science:

• Neuroscience
• Cognitive Science
• Neuroplasticity

Background:

• The human brain exhibits hemispheric lateralization, with specialized functions in each hemisphere.
• The impact of visual deprivation on the lateralization of visuospatial attention remains debated.
• Early visual experience may influence the development of spatial processing lateralization.

Purpose of the Study:

• To synthesize current empirical evidence on how visual deprivation affects the lateralization of spatial processes.
• To investigate whether the blind rely on different sensory inputs for spatial tasks compared to sighted individuals.
• To clarify the role of hemispheric specialization in visuospatial attention in the absence of normal visual development.

Main Methods:

• Review of empirical studies examining spatial tasks in blind and sighted populations.
• Analysis of evidence related to line bisection, mirror symmetry, and localization tasks.
• Synthesis of findings on hemispheric dominance and spatial processing in visual deprivation.

Main Results:

• Spatial processes in blind individuals are primarily supported by a right hemispheric network, similar to sighted individuals.
• Right-hemisphere dominance for spatial tasks appears more pronounced in the blind, indicated by a greater leftward bias.
• Increased involvement of the right parietal cortex and recruitment of the right occipital cortex are observed in blind individuals during spatial tasks.

Conclusions:

• Visual deprivation does not abolish right-hemisphere dominance for spatial processing but accentuates it.
• Enhanced right-hemisphere dominance in the blind is likely a result of cross-modal plasticity.
• The blind brain shows altered recruitment of cortical areas, particularly the parietal and occipital lobes, for spatial functions.