Visual system plasticity in mammals: the story of monocular enucleation-induced vision loss

Abstract

The groundbreaking work of Hubel and Wiesel in the 1960’s on ocular dominance plasticity instigated many studies of the visual system of mammals, enriching our understanding of how the development of its structure and function depends on high quality visual input through both eyes. These studies have mainly employed lid suturing, dark rearing and eye patching applied to different species to reduce or impair visual input, and have created extensive knowledge on binocular vision. However, not all aspects and types of plasticity in the visual cortex have been covered in full detail. In that regard, a more drastic deprivation method like enucleation, leading to complete vision loss appears useful as it has more widespread effects on the afferent visual pathway and even on non-visual brain regions. One-eyed vision due to monocular enucleation (ME) profoundly affects the contralateral retinorecipient subcortical and cortical structures thereby creating a powerful means to investigate cortical plasticity phenomena in which binocular competition has no vote.In this review, we will present current knowledge about the specific application of ME as an experimental tool to study visual and cross-modal brain plasticity and compare early postnatal stages up into adulthood. The structural and physiological consequences of this type of extensive sensory loss as documented and studied in several animal species and human patients will be discussed. We will summarize how ME studies have been instrumental to our current understanding of the differentiation of sensory systems and how the structure and function of cortical circuits in mammals are shaped in response to such an extensive alteration in experience. In conclusion, we will highlight future perspectives and the clinical relevance of adding ME to the list of more longstanding deprivation models in visual system research.

Altered white matter structure in the visual system following early monocular enucleation

“…In an attempt to account for this uncertainty, we have presented several potential mechanisms for each of the significant changes observed in the diffusion measures. Our rationale for the mechanisms put forward is supported by behavioral neuroimaging findings (e.g., fMRI, proton density scans) in other forms of visual deprivation [Shimony et al, ; Shu et al, ] and controls, and postmortem results from monocularly enucleated animals [Nys et al, ; Toldi et al, ]. Moreover, given that we are using standardized methods and comparing between groups, we are confident that our findings reflect true differences between participants who have undergone early monocular enucleation and binocularly intact controls.…”

Comparative ultrastructural features of excitatory synapses in the visual and frontal cortices of the adult mouse and monkey

“…Based on data presented here, the mechanisms of synaptic plasticity observed from these studies in mouse V1 may similarly apply to mouse FC (e.g., Gavornik & Bear, ). However, the synaptic features of mouse frontal and visual areas are distinct from the analogous monkey visual and frontal areas, and thus, mechanisms for plasticity likely differ between rodents and primates (e.g., Nys, Scheyltjens, & Arckens, ; Testa‐Silva et al, ; Verhoog et al, ).…”

Interleukin 4 Leads to Sustained Phosphorylation of the STAT6 and ERK Pathways in the Retina and Disrupts Subcortical Visual Circuitry in Rodents

“…Our data showed that an acute intravitreal injection with IL-4 leads to a topographical disruption in the untreated ipsilateral retinotectal axons, suggesting that IL-4 change the balance between binocular inputs to synaptic sites in the SC. Actually, different studies have demonstrated that lesion and/or inflammatory manipulations in one eye change the connectivity of the other eye [12,28].…”