Congenital visual pathway abnormalities: a window onto cortical stability and plasticity

• Maps are a basic organization feature of the brain and rely on organized pathways.
• Congenital visual pathway abnormalities provide insight into developmental plasticity.
• Chiasma abnormalities interleave visual maps while preserving basic perception.
• Update of classification of visual cortex organization in chiasma abnormalities.
• Human developmental mechanisms are conservative and highlight cortical adaptations.

Sensory systems project information in a highly organized manner to the brain, where it is preserved in maps of the sensory structures. These sensory projections are altered in congenital abnormalities, such as anophthalmia, albinism, achiasma, and hemihydranencephaly. Consequently, these abnormalities, profoundly affect the organization of the visual system. Surprisingly, visual perception remains largely intact, except for anophthalmia. Recent brain imaging advances shed light on the mechanisms that underlie this phenomenon. In contrast to animal models, in humans the plasticity of thalamocortical connections appears limited, thus demonstrating the importance of cortical adaptations. We suggest that congenital visual pathway abnormalities provide a valuable model to investigate the principles of plasticity that make visual representations available for perception and behavior in humans.