Monocular deprivation
Encyclopedia
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 (4–5 weeks-old in mice (Gordon 1997)). This manipulation serves as an animal model for amblyopia
, a permanent deficit in visual sensation not due to abnormalities in the eye (which occurs, for example, in children who grow up with cataracts - even after cataract removal, they do not see as well as others).
David Hubel and Torsten Wiesel
(who won the Nobel prize in Physiology for their elucidation of receptive field
properties of cells in primary visual cortex) first performed the technique in felines
(which, although less closely related evolutionarily to humans even than rodents, have a remarkably similar visual system to ours). They found that ocular dominance column
s (the orderly clustering of V1 neurons representing visual input from one or both eyes) are 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 . This physiological change was a 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 (Fig. 1 - Effect of monocular deprivation on ocular dominance columns. Light areas represent V1 neurons receiving input from an eye which has been injected with radioactive amino acid. Dark areas represent neurons receiving input from the other, noninjected, eye. Image A represents normal ocular dominance columns; Image B represents ocular dominance columns after monocular deprivation). These results were confirmed in the monkey.
In felines and monkeys, the critical period
(the period during which deprivation could cause permanent deficits) lasts until about 4 months of age. Depriving an eye for even a few days during this period is sufficient to cause major changes in ocular dominance column anatomy and physiology.
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
plasticity
Neuroplasticity
Neuroplasticity is a non-specific neuroscience term referring to the ability of the brain and nervous system in all species to change structurally and functionally as a result of input from the environment. Plasticity occurs on a variety of levels, ranging from cellular changes involved in...
. Generally, one of an animal's eyes is sutured shut during a period of high cortical plasticity (4–5 weeks-old in mice (Gordon 1997)). This manipulation serves as an animal model for amblyopia
Amblyopia
Amblyopia, also known as lazy eye, is a disorder of the visual system that is characterized by a vision deficiency in an eye that is otherwise physically normal, or out of proportion to associated structural abnormalities of the eye...
, a permanent deficit in visual sensation not due to abnormalities in the eye (which occurs, for example, in children who grow up with cataracts - even after cataract removal, they do not see as well as others).
David Hubel and Torsten Wiesel
Torsten Wiesel
Torsten Nils Wiesel was a Swedish co-recipient with David H. Hubel of the 1981 Nobel Prize in Physiology or Medicine, for their discoveries concerning information processing in the visual system; the prize was shared with Roger W...
(who won the Nobel prize in Physiology for their elucidation of receptive field
Receptive field
The receptive field of a sensory neuron is a region of space in which the presence of a stimulus will alter the firing of that neuron. Receptive fields have been identified for neurons of the auditory system, the somatosensory system, and the visual system....
properties of cells in primary visual cortex) first performed the technique in felines
Felinae
Felinae is a subfamily of the family Felidae which includes the genera and species listed below. Most are small to medium-sized cats, although the group does include some larger animals, such as the Cougar and Cheetah....
(which, although less closely related evolutionarily to humans even than rodents, have a remarkably similar visual system to ours). They found that ocular dominance column
Ocular dominance column
Ocular dominance columns are stripes of neurons in the visual cortex of certain mammals that respond preferentially to input from one eye or the other. The columns span multiple cortical layers, and are laid out in a striped pattern across the surface of the striate cortex...
s (the orderly clustering of V1 neurons representing visual input from one or both eyes) are 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 . This physiological change was a paralleled by dramatic anatomical changes. The layers representing the deprived eye in the lateral geniculate nucleus
Lateral geniculate nucleus
The lateral geniculate nucleus is the primary relay center for visual information received from the retina of the eye. The LGN is found inside the thalamus of the brain....
of the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
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 (Fig. 1 - Effect of monocular deprivation on ocular dominance columns. Light areas represent V1 neurons receiving input from an eye which has been injected with radioactive amino acid. Dark areas represent neurons receiving input from the other, noninjected, eye. Image A represents normal ocular dominance columns; Image B represents ocular dominance columns after monocular deprivation). These results were confirmed in the monkey.
In felines and monkeys, the critical period
Critical period
This article is about a critical period in an organism's or person's development. See also America's Critical Period.In general, a critical period is a limited time in which an event can occur, usually to result in some kind of transformation...
(the period during which deprivation could cause permanent deficits) lasts until about 4 months of age. Depriving an eye for even a few days during this period is sufficient to cause major changes in ocular dominance column anatomy and physiology.