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Psychology 4051

Psychology 4051. Visual System Plasticity. Visual System Plasticity. The first decade of life represents a period of substantial development of the visual system. This is also a period of plasticity during which connections to the visual cortex are susceptible to environmental insult.

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Psychology 4051

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  1. Psychology 4051 Visual System Plasticity

  2. Visual System Plasticity • The first decade of life represents a period of substantial development of the visual system. • This is also a period of plasticity during which connections to the visual cortex are susceptible to environmental insult. • This period represents a critical/sensitive period during which normal visual experience is necessary for the formation of connections to the visual cortex.

  3. Visual System Plasticity • Visual deprivation caused by visual insult can impede the formation of these connections. • During this time the eyes are in competition to form cortical connections. • Monocular visual deprivation can severely impair connections from the deprived eye.

  4. Animal Studies • Hubel and Wiesel have conducted numerous studies indicating that early visual deprivation causes severe changes to the visual system. • Cats and monkeys generally have an eye sutured shut early in life. • Animal undergo single cell recordings • In animals, the critical period appears to be between eye opening (or birth) and puberty.

  5. Animal Studies • The length of the visual deprivation and the timing of the deprivation is very important. • Longer deprivation is generally more drastic. • But there are periods in which animals are extremely sensitive even to short periods of deprivation.

  6. Anatomical/Physiological Effects • There are no effects on cells in the retina. • LGN cells corresponding to the deprived eye are smaller but respond normally. • Most of the effects are in the visual cortex. • Overall, there is a decline in the number of cortical cells driven by the deprived eye. • Found in all cortical layers.

  7. Anatomical/Physiological Effects • Animals who are forced to use the deprived eye later, often behave as though they are blind. • Researchers have also investigated the effects of surgically-induced strabismus. • Most cells in the visual cortex are monocular.

  8. Treatment • While in this period of plasticity some of the effects of monocular deprivation can be reversed by reverse suturing. • Sewing the other eye shut to force the use of the deprived eye. • If done during the critical period, the deprived eye regains cortical connections and acuity improves.

  9. Human Studies • Researchers have investigated the effects of naturally occurring deprivation in humans by looking at children who had cataracts. • Opacity on the lens that prevents the formation of a sharp image. • These studies confirm that the critical period lasts from birth to 10 years.

  10. Human Studies • Longer periods produce more severe effects, but timing is also important. • Leads to poorer visual acuities. • Early deprivation tends to produce drastic effects. • The effects of bilateral cataracts are far less severe. • Competition between the eyes is not compromised.

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