Patterns of Individual Variation in Visual Pathway Structure and Function in the Sighted and Blind

Area of Science:

• Neuroscience
• Neuroimaging
• Human Anatomy

Background:

• Blindness leads to significant structural and functional brain changes, with considerable individual variability.
• Correlated variation exists in visual pathway structures among sighted individuals.
• Understanding how blindness affects these normal variation patterns is crucial.

Purpose of the Study:

• To investigate if blindness alters the inherent patterns of anatomical variation in the central visual pathway.
• To determine if these patterns are maintained or modified by the absence of sight.
• To explore the relationship between anatomical variation and functional measures in blind and sighted individuals.

Main Methods:

• Structural MRI was used to derive eight measures of central visual pathway anatomy in 59 sighted and 53 blind individuals.
• Functional MRI and diffusion tensor imaging were employed to assess cross-modal responses and white matter integrity.
• Statistical analyses identified clusters of correlated anatomical variation and their relationship with functional data.

Main Results:

• Significant differences in mean visual pathway anatomy were observed between sighted and blind cohorts.
• Three clusters of correlated anatomical variation were identified, including V1 surface area, pericalcarine volume, and V1 cortical thickness, which were consistent in both groups.
• These anatomical clusters were differentially related to functional MRI and diffusion tensor imaging measures, and changes were graded by the timing of blindness onset.

Conclusions:

• The patterns of anatomical variation in the central visual pathway are largely preserved despite blindness.
• Brain alterations due to blindness appear to exist on a continuum with normal variation found in sighted individuals.
• The timing of blindness onset influences the degree of anatomical change, suggesting a graded effect on brain structure.