Bonfils, M. | Search bioRxiv

bioRxiv2026

Cue-guided performance is disrupted during pedunculotegmental-induced motor arrest

Optogenetic stimulation of the rostral pedunculotegmental nucleus (PTg) induces global motor arrest, but it remains unclear whether this is merely a suppression of motor activity or a broader disruption of brain processes required to guide action. We developed a visuospatial cue task for rats, to test if sensory information presented during PTg-induced arrest can guide later responses. Here, we show that optogenetic stimulation during cue presentation reduces accuracy to chance level. By moving stimulation to only before or only after the cue, we found that performance was only affected when stimulation and cue presentation overlapped, that rats recover cue-guided behavior almost immediately at the end of stimulation, and that stimulation does not appear to abolish responses based on cue information acquired before arrest. These findings indicate that stimulation of the rostral PTg does not only pause motor output but transiently disrupts the ability to process and use cue information effectively.

neuroscience↗

bioRxiv2024

Spatial and network principles behind neural generation of locomotion

Generation of locomotion is a fundamental function of the spinal cord, yet the underlying principles remain unclear. In particular, the relationship between neuronal cell types, networks and functions has been difficult to establish1,2. Here, we propose principles by which functions arise primarily from spatial features of the cord. First, we suggest that projections of distinct cell types constitute an asymmetrical "Mexican hat" topology, i.e. local excitation and surrounding inhibition with dissimilar length of projection along the rostro-caudal axis. Second, this projection topology constitutes the mechanism of rhythm- and pattern generation of mammalian locomotion. Third, the role of segregation of cell types in the transversal plane is for descending fibers to find appropriate targets. Modulation of these targets allows control of motor activity by adjusting the symmetry of the projection topology. We extract these principles via a model of the mouse spinal cord, where networks are constructed by probabilistic sampling of synaptic connections from cell-specific projection patterns, which are based on previous studies3, 4. The cell-type distributions are derived from single-cell RNA sequencing combined with spatial transcriptomics5. We find that essential aspects of locomotion are readily reproduced and controlled without requiring parameter optimization, and several experimental observations can now be explained mechanistically. Further, two main features are predicted: propagating bumps of neural activity during rhythmical activity and formation of static bumps during arrest and posture. Besides linking cell types, structure and function, we propose our approach as a new theoretical framework for motor control.

neuroscience↗