Research Supporting Selective Rearing Resulting in Neural Plasticity

Neural plasticity has been of interesting to researchers for sometime. The idea that the brain is plastic and can adapt to different situations is not only fascinating, but opens up new avenues as far as medical and mental health treatments. As such, there has been a great deal of research surrounding "selective rearing." Selective rearing deals with visual perception and how vision is related to the manner in which the brain processes it (Kinney, 2010). In order to study this, researchers have commonly turned to animal subjects, such as was the case with a study done on kittens. The experiment involved raising kittens in a "selective" environment in which they were exposed to only horizontal lines. In these tests, the kittens' visual neurons only responded to horizontal stimuli, which oddly enough allowed the kittens to detect only vertical lines (Bishop, 1982).

One specific experiment by Blakemore and Cooper (1970) kept kittens in the dark except for exposure to vertical or horizontal lines five hours a day. This went on for five months before the kittens were taken out and tested. Tovee (1996) explains the kittens behavior as displaying "a number of defects in their visual behavior." Just as explained earlier, the kittens were jerky in their movements, often clumsy, and were blind to any line at a right angle to the line they were exposed to (Tovee, 1996). While it seems odd that these kittens would experience such drastic changes after only five months, Rhawn explains that if a being (such as kitten or human) is reared in an abnormal environment (such as in the dark with exposure only to vertical or horizontal lines for five ours a day), the "limbic system nuclei will atrophy, random interconnections will be maintained, or neural pathways will develop abnormally" (Rhawn, 1999).

Another experimental method used on cats was one which prevented continual retinal movement. This was done by "stroboscopic illumination," a method in which the car is reared within a strobe light type device, which prevents the cat from moving its retina in the same way a typical cat (or even person) would (Pasternak & Merigan, 1979). The cats raised in this selective way were found to have a deficit in motion perception due to a "deficit in the direction selectivity of cortical cells" (Tovee, 1996).

As related to neural plasticity, it is noted that for the rearrangement of synaptic transmission within the visual cortex to occur, researchers had to expose the research subjects at a young age (Bishop, 1982). As is commonly known about the brain's plasticity, it is most plastic at a young age. This is also true concerning visual perception, in which alterations to it can be made at a young age. This realization also means that visual perception is shaped within the visual cortex of the brain during a young age, or more specifically, during the critical period in the brain's development.

References

Kinney. (2010). Sensation and Perception. Retrieved October 15, 2009, from http://74.125.155.132/search?q=cache:4Nzi_Lh-LZkJ:cstl-cla.semo.edu/Kinney/PY366/protected/Chapter%25203%2520Review.doc+selective+rearing%3F&cd=9&hl=en&ct=clnk&gl=us&client=firefox-a

Bishop, B. (1982). Neural Plasticity: Part 2. Postnatal Maturation and Function-Induced Plasticity. Physical Therapy. 62(8).1132-1143. doi. N/a.

Blakemore, C. & Cooper, G.F. (1970). Development of the Brain Depends on the Visual Environment. Nature, 228, 477-478.

Pasternak, T., Merigan, W. H. (1979). Abnormal Visual Resolution of Cats Reared in Stroboscopic Illumination. Nature, 280, 313-314. doi: 10.1038/280313a0

Rhawn, J. (1999). Environmental Influences on Neural Plasticity, the Limbic System, Emotional Development & Attachment. Child Psychiatry and Human Development, 29, 187-203.

Tovee, M. J. (1996). An Introduction to the Visual System. New York: Cambridge University Press.