Monocular deprivation


Monocular deprivation is an experimental technique used by neuroscientists to study central nervous system plasticity. Generally, one of an animal's eyes is sutured shut during a period of high cortical plasticity. This manipulation serves as an animal model for amblyopia, a permanent deficit in visual sensation not due to abnormalities in the eye.

Background

and Torsten Wiesel first performed the technique in felines. Kittens, although less-closely related evolutionarily to humans even than rodents, have a remarkably similar visual system to humans. They found that ocular dominance columns were dramatically disrupted when one eye was sewn shut for 2 months. In the normal feline, about 85% of cells are responsive to input to both eyes; in the monocularly-deprived animals, no cells receive input from both eyes. The monocular deprivation often leads to amblyopia that is irreversible.
This physiological change was paralleled by dramatic anatomical changes. The layers representing the deprived eye in the lateral geniculate nucleus of the thalamus are atrophied. In V1, ocular dominance columns representing the open eye are dramatically enlarged, at the expense of cortical surface area representing the sutured eye. These results were confirmed in the monkey.
In felines, the critical period can last up to one year with the peak occurring around 4 weeks. In monkeys, the critical period peak is around 6 months. Depriving an eye, for even a few days, during this period is sufficient to cause major changes in ocular-dominance-column anatomy and physiology. However, the results of monocular deprivation in adult cats are not the same. The ocular dominance columns do not show results of being disturbed even after the adult cat has had one of its eyes shut for over a year.