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Sprint then stopped? The brain is wired to math to make it happen

Summary: The brain naturally applies the principles of calculus and the rules of acquired life integrated with sensory information to guide motor plans and actions.

source: Bakeware Institute for Learning and Memory

Your new apartment is two blocks down the street from the bus station but you were late today and saw the bus rolling in front of you. You are entering a full race. Your goal is to get to the bus as fast as you can and then come to a complete stop in front of the doors (which are never exactly in the same place along the sidewalk) to get in before they close. To stop quickly and accurately enough, a new MIT study on mice finds that the mammalian brain is ingeniously linked to implementing the principles of calculus.

One might think that a boisterous stop at a target after a flat run would be as simple as a reaction, but riding a bus or jogging straight to a visual landmark to earn a water reward (as mice did), is a learned, visually-oriented, and goal-oriented feat.

In such tasks, which are of great interest in the lab of senior author Mrijanka Sor, Newton Professor of Neuroscience at MIT’s Beckware Institute for Learning and Memory at MIT, the critical decision to switch from one (running) to another (stopping) behavior comes from the cerebral cortex, as it integrates The brain rules life acquired with sensory information to guide plans and actions.

“The target is where the cortex comes in,” said Suhr, a faculty member in the Department of Brain and Cognitive Sciences at MIT. “Where am I supposed to stop to achieve this goal of getting on the bus.”

Here, too, it becomes complicated. Mathematical models of behavior developed by postdoc and lead author of the study Eli Adam predicted that a “stop” signal that traveled directly from the M2 region of the cortex to areas in the brainstem, which actually control the legs, would be processed very slowly.

Adam, who has done work appearing in the magazine, said cell reports.

So how does the brain speed up the process? What Adam Wassore and co-author Taylor Jones found is that M2 sends the signal to an intermediate region called the hypothalamic nucleus (STN), which then sends two signals to two separate pathways that meet in the brainstem.

why? Because the difference caused by these two signals, one inhibitory and the other excitatory, the arrival of one directly after the other shifts the problem from one of integration, which is a relatively slow addition of inputs, to differentiation, which is a direct acknowledgment of change. Shift calculus performs the stop signal more quickly.

Adam’s model using systems and control theory from engineering accurately predicted the speed needed for a correct stop and that differentiation would be necessary to achieve this, but it took a series of anatomical investigations and experimental manipulations to confirm the model’s predictions.

First, Adam confirmed that M2 was actually producing a spike in neural activity only when the mice needed to achieve their trained goal of stopping at the milestone. It also showed that it sends the resulting signals to the STN. Other stops for other reasons did not use this route. Furthermore, the artificial activation of the M2-STN pathway forced the mice to stop and caused it to be artificially inhibited causing the mice to frequently bypass the landmark.

This indicates the motor cortex
Red (“mCherry”) staining highlights axonal projections from the M2 motor cortex. Of particular interest are those that lead to the hypothalamic nucleus (STN). Credit: Eli Adam/MIT Picower Institute

Then the STN definitely needed to send a signal to the brainstem – specifically the pedunculopontin nucleus (PPN) in the midcephalic motor area. But when the scientists looked at neural activity starting in M2 and quickly leading to PPN, they saw that different types of cells in the PPN responded with different timing. In particular, before stopping, the excitatory cells were active and their activity reflected the speed of the animal during the stop.

Then, looking at the STN, they saw two types of bursts of activity around the terminals—one slightly slower than the other—that were either transmitted directly to the PPN through excitation or indirectly through the substantia nigra (SNr) through inhibition. The net result of the interaction of these signals in the PPN was inhibition sharpened by excitation. This abrupt change can be quickly found through differentiation to implement stop.

“The inhibitory impulse followed by excitement can lead to a sharp increase [change of] Sur said.

The study is consistent with other recent research papers. Working with Picower Institute researcher Emery N. and last year, members of the Sur lab, including Adam, published a study showing how the cortex bypasses the brain’s reflexes inherent in visually-guided motor tasks.

Together, these studies contribute to an understanding of how the cortex can consciously control instinctive wired motor behaviors but also how important deeper regions, such as the STN, are for rapidly implementing goal-directed behavior. A recent review from the lab illustrates this.

Adam speculated that the “hyper-direct pathway” of connections from the cortex to the STN might have a broader role than fast shutdown, potentially extending beyond motor control to other brain functions such as interruptions and changes in thinking or mood.

Financing: The JPB Foundation, the National Institutes of Health, and the Simons Foundation’s Autism Research Initiative funded the study.

see also

This shows the diagram of the head of a man and a woman

About this movement, news of mathematics and neuroscience research

author: David Orenstein
source: Bakeware Institute for Learning and Memory
Contact: David Orenstein – Becker Institute for Learning and Memory
picture: Image credited to Eli Adam Institute / MIT Picower

original search: open access.
Dynamic control of visually guided movement through cortical-hypothalamic projectionsWritten by Mriganka Sur et al. cell reports


Summary

Dynamic control of visually guided movement through cortical-hypothalamic projections

Highlights

  • We developed a visually guided motion task to study the stop sign
  • The M2-STN projection sends a stop signal when the optically guided motion stops
  • Bidirectional M2-STN activity controls the arrest of visually guided movement
  • M2-STN pathways to MLR/PPN implement differentiation for rapid movement control

Summary

Target-directed mobility requires control signals that propagate from higher-order regions to regulate spinal mechanisms. The direct hypercorticosteroid pathway provides a short route for cortical information to reach motor centers in the brainstem.

We developed a task in which head-mounted mice run to a visual landmark and then stop and wait for a reward and examined the role of secondary motor cortex (M2) projections to the hypothalamic nucleus (STN) in movement control.

Results of behavioral modeling, calcium imaging, and optogenetic processing suggest that the M2-STN pathway can be recruited during visually guided movement to rapidly and precisely control the pedunculopontine nucleus (PPN) of the midbrain motor area through the basal ganglia.

By capturing physiological dynamics through feedback control model and analysis of neural signals in the M2, PPN and STN, we find that infrasternal cortical projections likely control PPN activity by differentiating the M2 error signal to ensure rapid input-output dynamics.

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