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Congenital blindness affects diencephalic but not mesencephalic structures in the human brain
Luca Cecchetti1,2, Emiliano Ricciardi3, Giacomo Handjaras1,2
1Laboratory of Clinical Biochemistry and Molecular Biology, Department of Surgery, Medical, Molecular Pathology, and Critical Area, University of Pisa, Pisa, Italy.
Brain Structure & Function
|January 7, 2015
Summary
Congenital blindness leads to significant volume reduction in specific thalamic nuclei, including the primary visual relay. However, mesencephalic structures like the superior and inferior colliculi remain unaffected, suggesting selective developmental changes in the brain.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Neuroimaging
Background:
- Early visual deprivation is known to impact visual cortical areas.
- Less is understood about how early blindness affects subcortical thalamic nuclei and mesencephalic structures.
Purpose of the Study:
- To investigate the volumetric changes in subcortical thalamic nuclei and mesencephalic structures in individuals with congenital blindness.
- To compare these changes with those in sighted individuals using MRI.
Main Methods:
- A multicenter study involving 29 individuals with congenital blindness and 29 sighted controls.
- Magnetic Resonance Imaging (MRI) was used to measure the volumes of the superior and inferior colliculi, and thalamic nuclei.
- Thalamic nuclei were parcellated based on atlas-derived thalamo-cortical connections.
Main Results:
- Congenitally blind individuals showed overall reduced volume in both left and right thalami compared to sighted controls.
- The lateral geniculate nucleus, the primary visual thalamic relay, was significantly reduced by 40% in the blind group.
- Associated thalamic nuclei projecting to temporal, prefrontal, occipital, and premotor cortical regions were also significantly reduced.
- Volumes of thalamic nuclei involved in auditory, motor, and somatosensory processing, as well as the superior and inferior colliculi, were not affected.
Conclusions:
- Early visual loss results in selective volumetric alterations within diencephalic structures, particularly the thalamus.
- Mesencephalic structures (superior and inferior colliculi) are not affected by visual deprivation.
- Changes in cortico-thalamic connectivity or intrinsic thalamic connectivity may explain the observed thalamic volume reductions.
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