Summary: Researchers explored how mice time their actions to receive rewards, focusing on the mesocortical brain pathway.
The study found that dopamine-mediated signals via D2 receptors are crucial for self-initiated movements. These signals increase activity just before action but not in response to cues.
The findings enhance our understanding of goal-directed behavior and its underlying brain mechanisms.
Key Facts:
- Dopamine signals via D2 receptors are key for self-initiated actions.
- Activity in the mesocortical pathway increases just before mice act.
- Study offers insights into goal-directed behavior and potential interventions for impulse control disorders.
Source: SPIE
Ever wondered how your brain decides when to act? Initiating actions with a specific goal in mind is a complex process.
Previous research has identified certain parts of the brain and chemical signals involved. However, it remains unclear what information these signals convey and how they spark initiative.
Recent research reported in Neurophotonics dives into this mystery by investigating how mice time their actions in pursuit of rewards, exploring the role of a specific brain pathway called the mesocortical pathway, in the context of self-initiated movement.
They created a task for mice where they could press a lever at will and receive a reward. The mice would receive a better reward if they waited longer before pressing.
The research team found that a certain type of brain signal, mediated by dopamine and its “D2” receptors, plays a crucial role in these self-timed actions. That brain signal kicks into gear just before the mice decide to press a lever but, surprisingly, doesn’t fire up when the mice respond to cues.
To understand better why that might be, the team used a novel imaging technique to observe the activity of these brain signals — just before the mice initiated their actions. They discovered a gradual increase in activity in certain parts of the brain about half a second before the self-timed presses.
Remarkably, this increase in activity occurred regardless of whether the mice pressed the lever quickly for a small reward or waited for a larger one.
According to senior author Takashi Sato, principal investigator in the Sato Brain Lab at the Medical University of South Carolina, “These findings offer tantalizing clues into the brain’s inner workings and contribute to a deeper understanding of how brains control goal-directed behavior.”
The research results raise some interesting questions: How might disruptions in the dopamine-mediated signaling pathway affect an individual’s ability to time their actions effectively? Are there parallels between the mechanisms observed in mice and those at play in human decision-making processes? Could manipulating dopamine receptors lead to novel interventions for conditions characterized by impaired impulse control, such as addiction or ADHD?
About this neuroscience research news
Author: Daneet Steffens
Source: SPIE
Contact: Daneet Steffens – SPIE
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Encoding of self-initiated actions in axon terminals of the mesocortical pathway” by Takashi Sato et al. Neurophotonics
Abstract
Encoding of self-initiated actions in axon terminals of the mesocortical pathway
Significance
The initiation of goal-directed actions is a complex process involving the medial prefrontal cortex and dopaminergic inputs through the mesocortical pathway. However, it is unclear what information the mesocortical pathway conveys and how it impacts action initiation. In this study, we unveiled the indispensable role of mesocortical axon terminals in encoding the execution of movements in self-initiated actions.
Aim
To investigate the role of mesocortical axon terminals in encoding the execution of movements in self-initiated actions.
Approach
We designed a lever-press task in which mice internally determine the timing of the press, receiving a larger reward for longer waiting periods.
Results
Our study revealed that self-initiated actions depend on dopaminergic signaling mediated by D2 receptors, whereas sensory-triggered lever-press actions do not involve D2 signaling. Microprism-mediated two-photon calcium imaging further demonstrated ramping activity in mesocortical axon terminals approximately 0.5 s before the self-initiated lever press. Remarkably, the ramping patterns remained consistent whether the mice responded to cues immediately for a smaller reward or held their response for a larger reward.
Conclusions
We conclude that mesocortical dopamine axon terminals encode the timing of self-initiated actions, shedding light on a crucial aspect of the intricate neural mechanisms governing goal-directed behavior.
