Tactile modulation of whisking via the brainstem loop: statechart modeling and experimental validation

Area of Science:

• Neuroscience
• Animal Behavior
• Computational Modeling

Background:

• Explorative whisking in rats is driven by central pattern generators (CPGs) but modulated by sensory feedback.
• The brainstem is a hypothesized site for sensory feedback influencing CPG activity during whisking.
• The precise interaction between sensory feedback and CPGs in whisking remains poorly understood.

Purpose of the Study:

• To investigate the interaction between sensory feedback and CPG activity in the rat whisking system.
• To model the brainstem loop involved in whisking behavior and sensory feedback.
• To elucidate the mechanism behind touched-induced pumps (TIPs) in whisking.

Main Methods:

• Developed a dynamic, bottom-up computational model of the rat brainstem whisking loop using statecharts.
• Used the touched-induced pump (TIP) phenomenon as a benchmark for model validation.
• Experimentally compared TIP occurrence in intact rats versus rats with severed sensory nerves.

Main Results:

• TIPs were shown to depend on sensory feedback, as evidenced by differences between intact and lesioned rats.
• The computational model ruled out several hypothesized feedback mechanisms for TIPs.
• A single mechanism, involving sensory feedback activating extrinsic retractor muscles, successfully simulated TIPs and predicted widespread whisker movement.

Conclusions:

• Touched-induced pumps (TIPs) are generated by sensory feedback activating extrinsic retractor muscles in the mystacial pad.
• The model successfully simulated TIPs, suggesting a specific interaction between sensory feedback and CPGs in the brainstem.
• Experimental validation confirmed model predictions, including TIPs in all ipsilateral whiskers, supporting the proposed feedback mechanism.