Wednesday, April 14, 2004

More on Left-Right Communication in the Nervous System
Why the Corpus Callosum is Important

Two items found via Science Daily:

Date: 4/12/2004

Brain's Left And Right Sides Work Together Better In Mathematically Gifted Youth

Washington -- There really may be something different about the brains of math-heads. Mathematically gifted teens did better than average-ability teens and college students on tests that required the two halves of the brain to cooperate, as reported  (PDF) in the April issue of Neuropsychology, published by the American Psychological Association (APA). 

[...] For the average teens and college students, the left brain hemisphere was faster for local matches and the right brain hemisphere was faster for global matches. This fit prior research, which has indicated that the left hemisphere is adept at processing visual "parts," in this case the letter details, while the right hemisphere is more adept at analyzing visual "wholes," in this case the global shapes of the big letters.

However, the mathematically gifted boys showed no such hemispheric differences. Those who were precocious in math were equally good at processing global and local elements with either hemisphere, suggesting more interactive, cooperative left and right brains.

Study finds nerve damage can affect opposite side of body
MGH report suggests previously unknown communication between nerve cells

BOSTON - April 2, 2004 - Researchers from Massachusetts General Hospital (MGH) have found physical evidence of a previously unknown communication between nerves on opposite sides of the body. In the May 2004 issue of Annals of Neurology, the scientists describe how cutting a major nerve in one paw of a group of rats resulted in a significant decrease in skin nerve endings in the corresponding area of the opposite limb. The study, released on the journal's website, may have major implications for the care of patients with nerve damage and also calls into question the common practice of using tissues on the opposite side of the body as controls in scientific experiments.

[...] It has been known for more than 100 years that, when a nerve is cut, skin nerve endings in the area supplied by that nerve quickly disappear. This is because nerve cell bodies are actually located near the spinal cord, and nerve fibers called axons extend into the limbs. When axons are severed, downstream nerve endings are cut off from the cell body and die.

Reports of opposite-side sensory effects of injury date back to the American Civil War. However, no connections are known to exist between nerve cells supplying corresponding areas on the left and right sides.

[...] In the current study, Oaklander and her co-author Jennifer Brown describe their experiment in three groups of rats - an experimental group in which the tibial branch of the sciatic nerve was cut in one hind paw and two control groups, one which had sham surgery and the other had no procedures. Within one week of injury, rats in the experimental group lost almost all skin nerve endings in the part of the paw supplied by the tibial nerve. Surprisingly, they also lost 54 percent of nerve endings in the corresponding area in the opposite paw. No changes were seen in either control group. The researchers also examined the opposite-limb-area supplied by the uncut nearby sural branch of the sciatic nerve and found no change in nerve endings.

"This loss of nerve fibers in the contralateral limb is so precise - being confined to areas innervated by the matching nerve - that the communication is likely to involve nerve cells or the supporting glial cells," says Oaklander, an assistant professor of Anesthesia and Neurology at Harvard Medical School. "We need to look into what regulates this communication and how it may be altered to help treat nerve injury and pain patients."