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Hope for Parkinson's: Discovering New Areas in the Motor Homunculus

There is some exciting news about a recent discovery on the new areas in the brain and how it helps people with Parkinson’s and the field of Neurofeedback.


You may have heard of motor homunculus before. It is a map of the brain that shows how various parts of the primary motor cortex control various parts of the body. The primary motor cortex in the precentral gyrus sends signals to the muscles to produce voluntary movements.

The motor homunculus was first described by Penfield in the 1930s, based on his experiments of stimulating the brain of patients during surgery. He found that stimulating different points along the motor cortex would elicit movements of different body parts, such as fingers, toes, lips, tongue, etc. He also noticed that the size of each body part on the map was proportional to how much control we had over it. For example, the hand and the mouth take up more space than the leg or the trunk.


The motor homunculus has been a classic model of brain organization for decades, but it turns out that it is not as accurate as we thought. A new study published in Nature by Gordon et al. (2023) https://www.nature.com/articles/s41586-023-05964-2 has revealed three previously overlooked motor homunculus areas.

These areas are not dedicated to specific body parts but rather to integrative, whole-body actions. They are also connected to other brain regions involved in action planning and pain perception.


The researchers used precision functional mapping (PFM) to measure the brain's activity using functional MRI while participants performed various tasks. They found that these three new areas were activated when participants performed complex movements involving the coordination of multiple body parts, such as rotating their wrists and feet simultaneously. They also found that these areas were connected to a network of brain regions called the salience network, which detects and responds to important stimuli, such as pain or reward.


These findings have important implications for Neurofeedback, a technique that uses real-time feedback of brain activity to help people learn to regulate their brain functions. Neurofeedback has been used to treat various conditions, such as ADHD, anxiety, depression, PTSD, chronic pain, and Parkinson's disease. One of the most common Neurofeedback protocols for Parkinson's disease is to train people to increase their activity in the inter-effector regions of the brain, which are located between the areas that control different body parts on the motor homunculus. The idea is that by enhancing these regions, people can improve their coordination and reduce their tremors.


However, this new study suggests that there may be additional effective regions to target for Neurofeedback training. The three new areas in the motor homunculus may be more relevant for integrative movements and action planning than the inter-effector regions. Moreover, these areas are also connected to the salience network, which may help people modulate their pain perception and emotional responses. Therefore, training people to increase their activity in these new areas may improve their motor function and quality of life.


This new research also reinforces the success of another Neurofeedback protocol for Parkinson's disease, which trains people to increase their activity in the supplementary motor area (SMA). The SMA is located above the primary motor cortex and is involved in initiating and planning complex movements.

Previous studies have shown that neurofeedback training of the SMA can improve motor symptoms and cognitive function in Parkinson's patients. The new study shows that one of the three new areas in the motor homunculus is directly adjacent to the SMA and shares some functional connectivity. This suggests that these two regions work together to coordinate integrative movements and that neurofeedback training in both regions may have synergistic effects.


In conclusion, this new study has revealed three new motor homunculus areas involved in integrative movements and action planning. These areas are also connected to other brain networks relevant to pain perception and emotional regulation. These findings have important implications for neurofeedback training and may offer new possibilities for improving motor function and quality of life in Parkinson's patients and other populations.


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