Pulvinar and total thalamus volumes are preserved following early monocular enucleation

Monocular enucleation, the surgical removal of one eye, occurs early in life and leads to changes in visual, auditory, and audiovisual processing in adulthood. These changes can be observed behaviorally, as well as through cortical structure and white matter connectivity of visual and auditory pathways. Subcortically, the thalamus is a critical sensory processing structure that modulates both unisensory and multisensory stimuli, which are later processed in the cortex. Previous studies have shown that following monocular enucleation, the lateral geniculate nucleus (LGN) is reduced in volume, although this reduction is less than predicted. In contrast, the medial geniculate body (MGB) is asymmetric but maintains its volume. Together, this may support the auditory and audiovisual enhancements observed following early monocular enucleation. Another key subcortical thalamic nucleus, the pulvinar, plays a broad role in human visual information processing and sensorimotor integration.

The current study used structural MRI to anatomically localize and measure the total pulvinar and its subnuclei, as well as total thalamus volume, in individuals who had undergone early monocular enucleation during postnatal maturation compared to binocularly intact controls.

Overall, people with one eye demonstrated preserved pulvinar and total thalamus volumes compared to binocularly intact controls.

The preserved structural volume of the pulvinar and total thalamus may support the intact lower-level auditory and audiovisual processing previously observed in individuals with one eye. The absence of pulvinar volume changes in this broad-function supporting, subcortical region builds on previous studies regarding thalamic plasticity after early monocular enucleation. These findings provide evidence that not all thalamic nuclei show measurable long-term volumetric alterations and that neural plasticity is both regionally and functionally dependent.