Automated Place Preference Paradigm for Optogenetic Stimulation of the Pedunculopontine Nucleus Reveals Motor Arrest-Linked Preference Behavior

TL;DR

This study introduces an automated system for optogenetic experiments that reveals how stimulating the rostral PPN in rats links motor arrest with place preference, suggesting a role in motivation and motor control.

Contribution

The paper presents a novel low-cost, automated closed-loop system for real-time behavioral and neural stimulation experiments in rodents.

Findings

Optogenetic stimulation of the PPN induces transient motor arrest.

Rats develop a place preference when motor arrest is paired with a specific location.

The system enables scalable, unbiased behavioral assays for neuroscience research.

Abstract

Understanding how the brain integrates motor suppression with motivational processes remains a fundamental question in neuroscience. The rostral Pedunculopontine nucleus, a brainstem structure involved in motor control, has been shown to induce transient motor arrest upon optogenetic or electrical stimulation. However, our current understanding of its potential role in linking motor suppression with motivational or reinforcement-related processes is still insufficient. To further explore the effects induced by PPN stimulations and infer the potential mechanism underlying its role involved in both motor and emotional regulation, we developed a fully automated, low-cost system combining real-time animal tracking with closed-loop optogenetic stimulation, using the OpenMV Cam H7 Plus and embedded neural network models. The system autonomously detects the rat's position and triggers optical stimulation upon entry into a predefined region of interest, enabling unbiased, unsupervised behavioral assays. Optogenetic activation of CaMKIIa-expressing neurons in the rostral PPN reliably induced transient motor arrest. When motor arrest was spatially paired with a defined region of interest, rats developed a robust place preference after limited training. These results suggest that rostral PPN activation can couple motor inhibition with reinforcement-related behavioral circuitry. Together, our work provides both a technical framework for scalable closed-loop neuroscience experiments and preliminary evidence that the rostral PPN may participate in coordinating motor suppression with motivational processes.