January 20, 2009
Higher Primates Evolved New Way To Control Hands

Humans and other higher primates developed fancier circuitry in the brain to support more complex sequences of movement. This enabled more complex usage of tools.

PITTSBURGH, Jan. 12 A new area of the cerebral cortex has evolved to enable man and higher primates to pick up small objects and deftly use tools, according to neuroscientists at the University of Pittsburgh School of Medicine and Pittsburgh's Veterans Affairs Medical Center.

The brain's primary motor cortex turns out to have neighboring "old" and "new" parts. In most animals, including cats, rats and some monkeys, the old primary motor cortex controls movement indirectly through the circuitry of the spinal cord, explained senior author Peter Strick, Ph.D., professor in the department of neurobiology at the School of Medicine and senior career scientist at the VA Medical Center.

But in man, the Great Apes and some monkeys, another area of the motor cortex developed and is now home to a special set of cortico-motoneuronal (CM) cells, he said. These cells directly control spinal cord motor neurons, which are the nerve cells responsible for causing contraction of shoulder, elbow and finger muscles. The direct control exerted by CM cells bypasses the limitations imposed by spinal cord circuitry and permits the development of highly complex patterns of movement, such as the independent finger action needed for playing an instrument or typing.

The development of greater ability to manipulate tools probably played synergistically with the development of more cognitive capacity in order to learn and remember what to use tools for. So this development probably created selective pressures for further evolution of the brain.

Share |      Randall Parker, 2009 January 20 10:25 PM  Brain Evolution

Fat Man said at January 21, 2009 7:56 AM:

Now I know why I can't play the piano.

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