Neuroplasticity | Ankur Gupta Research

Motor Cortex Flexibility: How Monkeys Learn New Skills

Have you ever wondered how learning new movements changes the brain? My research looked at how adult monkeys' brains adjust when they learn fresh motor tasks. It turns out, their motor cortex (the part of the brain controlling movement) is surprisingly flexible, reshaping itself depending on what body parts are used most in training.

Monkey see, Monkey learn, Monkey do

I trained a group of monkeys to perform two challenging tasks: one using their fingers and wrists (like turning a knob), and another using shoulders and elbows (like reaching for something). Some monkeys learned both tasks, but in different orders, while others tried just one.

After the monkeys were skilled at their tasks, I used safe, gentle brain stimulation to map out which parts of their motor cortex controlled specific joints. I also recorded how single neurons fired during these tasks and measured muscle activity.

The Big Findings

A simplified illustration of finger/wrist (shown as palm) and elbow/shoulder (shown as monkey arm) representation in the motor cortex after extensive training utilizing finger/wrist and elbow/shoulder tasks.

I found the maps in the monkeys’ brains changed depending on the task. When a monkey practiced the finger-and-wrist task, the part of its brain controlling fingers and wrists grew larger. When the monkey switched to the reaching task, the part controlling shoulder and elbow movements grew instead. This expansion wasn’t permanent and retraining could shrink or expand these areas again, so it’s reversible.

Interestingly, a spot in the motor cortex could switch what joint it controlled depending on the current training. Sometimes, after switching tasks, a brain area that used to move a finger could now make a shoulder move, and vice versa. About 80% of these changes followed the demands of the new task.

I also found that these changes weren’t just limited to neighboring joints. Sometimes, a site controlling fingers would start controlling shoulders, skipping over wrists and elbows.

Local Brain Neighborhoods Matter

What caused these flexible changes? I looked closely at each spot and its neighbors in the brain. If a spot’s neighbors all controlled the same joint, it was less likely to change. But if the neighborhood had a mix (say, some controlling fingers and others elbows) that spot was more likely to switch when the task changed.

What About Neuron and Muscle Activity?

Surprisingly, the firing patterns of individual neurons showed a different story. Across the motor cortex, neurons fired in a task-related way, no matter which joint they were connected to or what part of the brain they sat in. Whether the task used fingers or shoulders, the number of neurons focused on the job was about the same. This pattern held up even when looking just at primary motor cortex.

Muscles behaved similarly. Both finger/wrist and shoulder/elbow muscles showed directional tuning during movements, though the strength of muscle activation depended on the task. In the wrist task, the shoulder muscles weren’t activated as strongly, probably because the arm was fixed. But in the reach task, both shoulder and finger muscles worked together.

Why Does This Matter?

My work shows that adult brains stay flexible and can reorganize their movement maps as needed, not just when learning something complex, but even when switching back and forth between tasks. This might influence how recovery after brain injuries works and points to how skill learning involves recruiting bigger areas of the cortex for fine control.

Rather than just boosting activity in a few “task-relevant” cells and muscles, the brain seems to expand the whole map and lets lots of neurons join the process, regardless of the main joint involved. The system is dense and broad, not selective and sparse.

The Takeaway

Learning a new movement, whether with fingers or shoulders, can reshape the motor cortex in adult monkeys. The changes depend on what’s needed for the current task and are driven both by local brain organization and by the demands of movement itself. At the same time, the activity of neurons and muscles remains widespread and flexible, allowing for efficient control and quick adaptation.

To read more:

Gupta A., Nashef A., Israely S., Segal M., Harel R., & Prut Y. (2020). Motor cortical plasticity in response to skill acquisition in adult monkeys. bioRxiv.