Collateral-defined prefrontal-striatal circuits partition behavioral vigor during appetitive goal pursuit
This study demonstrates that behavioral vigor during appetitive goal pursuit is selectively regulated by two distinct collateral-defined prefrontal-striatal subnetworks, where DMS/PL neurons drive action initiation while DMS/aIC neurons constrain reward approach.
Original paper dedicated to the public domain under CC0 1.0 (https://creativecommons.org/publicdomain/zero/1.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Motivated behavior is the engine of life, the internal drive that pushes an animal to seek food, find shelter, or pursue a mate. Yet this drive is not a single, unbroken force. It unfolds as a sequence of distinct steps: the decision to move, the physical act of moving, the approach toward a goal, and the final consumption of a reward. Scientists have long known that the intensity, or "vigor," of these actions changes depending on how much an animal wants something or how tired it is. But a fundamental question remained unanswered: does the brain regulate the speed and energy of every step in this sequence with a single switch, or does it use different controls for different parts of the journey? Understanding this distinction is crucial because it reveals how the brain breaks down complex goals into manageable, independent actions, a process essential for adapting to a changing world.
A team of researchers at Shanghai Jiao Tong University and Fudan University has now mapped how the brain manages this complexity. They discovered that the brain does not treat the start of an action and the approach to a reward as a single unit. Instead, it uses two specialized, parallel circuits to control them separately. By observing mice as they worked for a sugary reward, the scientists found that the energy used to start a task is regulated differently than the energy used to reach the finish line. When the mice became full and less hungry, they slowed down significantly before they even started moving, but once they were moving toward the food, their speed remained steady. This suggested that the brain has a specific mechanism for deciding whether to begin an effort, and a different one for maintaining the effort once it has started.
To find the neural basis of this separation, the researchers focused on a specific highway in the brain: the connection between the dorsomedial prefrontal cortex, a region involved in planning and decision-making, and the dorsomedial striatum, an area critical for learning and action. They knew that neurons in the prefrontal cortex often send branches to multiple destinations, much like a telephone line that splits to connect to different offices. The team asked whether these branching neurons, which all send signals to the striatum, might also be sending signals to other places that define their specific job. Using advanced imaging and genetic tagging, they identified two distinct groups of neurons within this pathway. One group, which also sent branches to the prelimbic cortex, was active when the mice were deciding to start a task. The other group, which sent branches to the anterior insular cortex, was active when the mice were moving toward the reward.
The researchers then tested the function of these two groups by using light to turn them on or off, a technique that allows scientists to control specific cells with high precision. When they activated the "start" neurons, the mice began their tasks much faster. When they silenced these same neurons, the mice hesitated, taking longer to begin. In contrast, manipulating the "approach" neurons had no effect on how quickly the mice started. Instead, activating the approach neurons made the mice move more slowly toward the reward, while silencing them made the mice rush forward. This revealed a clear division of labor: one circuit acts as a gas pedal for initiating action, while the other acts as a brake for the approach phase, ensuring the animal does not move too recklessly toward its goal.
The study also showed that these two circuits receive information from different parts of the brain. The "start" neurons get more input from areas associated with memory and internal state, while the "approach" neurons receive more input from the thalamus, a relay station for sensory information. This wiring suggests that the decision to start is heavily influenced by the animal's internal motivation and recent history, whereas the movement toward the goal is tuned to immediate sensory cues and the physical reality of the environment.
By showing that the brain partitions the vigor of goal pursuit into separate, collateral-defined circuits, this work provides a new understanding of how motivation is organized. It suggests that the brain does not simply turn up the volume on a single "drive" signal. Instead, it uses a sophisticated network of specialized pathways to independently control the decision to act and the execution of the approach. This allows an animal to be highly motivated to start a task while carefully modulating how it moves toward the reward, or to hesitate at the start while maintaining a steady pace once the journey has begun. This fine-grained control ensures that behavior remains flexible and efficient, adapting to the specific demands of the moment rather than following a rigid, one-size-fits-all script.
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