You may not remember much calculus from school, but your brain has it on lock when it comes to sprinting and signaling when to stop. Ever almost miss a flight and ran straight for the gate? Some might think it’s just really good reflexes to stop right when you make it, but a new MIT study in mice finds that there’s more to it. As it turns out, your brain is “wired” to do math under such circumstances.
It’s one thing for the brain to process behavior and sensory when it comes to running, but it’s another to process when and where to stop after you reach your end place or your “goal.”
“The goal is where the cortex comes in, where am I supposed to stop to achieve this goal?” says Mriganka Sur, a faculty member of MIT’s Department of Brain and Cognitive Sciences, in a statement. This is the million-dollar question that she and her colleagues have set to examine.
The behavioral mathematical models that lead author Elie Adam developed predicted that a “stop” signal moving directly from the M2 region of the cortex to the brainstem — which controls the legs — would be processed too slowly to be the sole reason your brain knows to stop moving.
From this, they deduced that it was math that speeds it up. Through their experiments with different models, the team found that the M2 sends a signal to an intermediary region called the subthalamic nucleus (STN), which then sends out two opposing signals down two separate paths that meet up in the brainstem. One signal is inhibitory while the other is excitatory, and each signal arrives one right after the other, making it into a process of differentiation, which is a direct way of recognizing a change.
“An inhibitory surge followed by excitation can create a sharp [change of] signal,” says Sur. This represents a calculus shift that is able to provide a much quicker and more efficient stop signal.
Adam’s model allowed the team to conclude that M2 was producing a powerful surge in neural activity when the mice needed to achieve a goal of stopping at a specific spot. He also showed it was sending the resulting signals to the STN. Other stops without the pressure of an end goal did not show this response.
The findings of this study work together with previous works and studying neurostimulation in these areas of the brain, specifically in the STN, may help better understand movement disorders like Parkinson’s disease. The team also hopes that they can expand on this work, contributing to a greater understanding of movement related to goal-driven behaviors.
This study is published in the journal Cell Reports.