Brain analyzes reveal an organization based on action in people born without hands

Conventional wisdom in neuroscientists suggest that the motor functions of the brain are organized around the body, which means that certain brain areas control the hand; others the foot. An emerging alternative theory is that parts of the brain can be organized by types of action, such as reaching or using tools, regardless of the body part used to complete the task.

Researchers at the University of Georgetown have recently decided to understand these theories, because knowing how the brain is organized around the function in relation to the part of the body has deep implications for rehabilitation and the return to the function of a person after a brain injury.

The results are published in the Proceedings of the National Academy of Sciences. The work is entitled “The principles of mapping of the action type extend beyond evolutionary actions, even in people born without hands.”

“If the engine control is partly based on actions rather than body parts, it is possible that the brain can use this flexibility to compensate for the loss of specific members,” said the main author of the study, Ella Striem-Amit, Ph.D., assistant professor of neuroscience at the Georgetown University School of Medicine.

To better understand the emerging theory, Striem-Amit and a team of neuroscientists conducted a new study with volunteers who were born without hands, and rather use their feet for daily tasks with and without tools.

Using IRM brain scanners, researchers have shown that in these individuals, the brain areas generally involved in the use of the manual tool are still active – even if individuals used their feet, not their hands. This observation is consistent with the same preference for action for witness participants, who take action with their hands or their feet.

“We have found that certain regions of the brain care about the type of action that a person is done and not if this action has been carried out with the hand or with the foot,” said Florencia Martinez Addiego, a graduate student of the Striem-Amit laboratory who led the study.

She said that it seems that this organization could occur without typical motor experience, providing evidence of the type of action as a basic driving factor in motor organization and development.

Interestingly, it was not true for all brain areas.

“The main engine cortex, which is closely mapped to the body, has not reorganized for the use of feet -based tools, even in people who have used tools with their feet all their lives,” said Dr. Yuqi Liu, a former postdoctoral scholarship holder who also directed the study. “This suggests that certain brain areas demonstrate more plasticity than others.”

However, the study reveals a kind of organization of the brain which goes beyond the body – one which is abstract and centered on action, and which develops even without typical experience. They also develop the previous results of the organization of the brain and plasticity in blindness and deafness.

“Many regions of the brain can be more flexible than you thought before, especially at the start of development,” said Striem-Amit. “Just like certain areas involved in perception react to information from any meaning, certain parts of the engine system can represent actions in a way that is generalized between the parts of the body – without that with which a person was born.”

The participant of the Alvin Law study, 65, was born unarmed, a congenital malformatics caused by the use of thalidomide by her mother, a commonly prescribed medication for morning nausea in the 1950s and 1960s.

He says that even if prostheses are not suitable for him because he learned to use his legs and feet for very young daily tasks, he recognizes that they are important for people who lose their members and that the learned knowledge of this study can improve them.

“I can’t even imagine what would be to lose a member of any kind, for what cause,” said Law. He hopes that his contributions will be able to help people find a good quality of life through improved technologies.