New brain area evolved to help humans with complex movements

Washington, Jan 13 (ANI): Neuroscientists at the University of Pittsburgh School of Medicine and Pittsburgh's Veterans Affairs Medical Center have discovered that a new area of the cerebral cortex in brain has evolved, which has provided man and higher primates with the ability to pick up small objects and deftly use tools.

The brain's primary motor cortex has been found to have neighbouring "old" and "new" parts.

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 said that the majority of animals, including cats, rats and some monkeys, the old primary motor cortex controls movement indirectly through the circuitry of the spinal cord.

However, he said that in man, the Great Apes and some monkeys, another area of the motor cortex developed, which now homes a special set of cortico-motoneuronal (CM) cells.

The CM 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.

"What we've shown is that along with evolution of direct control over motor neurons, a new cortical area has evolved that's right next to the old one. We still have much the same spinal machinery the frog has, but the new cortical area with CM cells endows humans with the superior hand skills to manufacture and use tools - an especially human trait," said Strick.

The researchers conducted a series of experiments in which rabies virus was injected into single muscles in the shoulders, elbows or fingers of monkeys.

The virus, chosen because of its unique ability to travel between networked nerve cells, was tracked to locate CM cells in the primary motor cortex.

Strick indicated that the direct connection from the cortex to motor neurons is not present at birth, but develops during the first few months of life and becomes fully mature around two years of age.

Thus, the progress of an infant's motor skills is a display of the establishment of these connections.

The findings of the study have been published in the early online edition of the Proceedings of the National Academy of Sciences. (ANI)