Stimulus predictability mediates a switch in locomotor smooth pursuit performance for Eigenmannia virescens

Area of Science:

• Comparative physiology
• Animal behavior
• Neuroethology

Background:

• Weakly electric fish use an electric sense for navigation and social interactions.
• Eigenmannia virescens (glass knifefish) utilize an anal fin for precise forward and backward locomotion.
• Tracking moving objects is crucial for survival and foraging in many aquatic species.

Purpose of the Study:

• To investigate the tracking dynamics of Eigenmannia virescens in response to predictable and unpredictable visual stimuli.
• To determine if fish employ internal dynamical models for motion tracking.
• To explore the potential for stimulus-mediated adaptation in fish behavior.

Main Methods:

• Fish behavior was recorded while they tracked a computer-controlled moving refuge with varying trajectories (sinusoidal and sum-of-sines).
• Quantitative analysis of fish and refuge trajectories to assess tracking coherence, linearity, and error.
• Comparison of tracking performance between predictable (single-sine) and unpredictable (sum-of-sines) stimuli.

Main Results:

• High coherence between fish and refuge trajectories indicated generally effective tracking.
• Nonlinear tracking differences emerged between predictable and unpredictable stimuli, suggesting stimulus-mediated adaptation.
• Fish exhibited reduced tracking error and phase lag when tracking predictable sinusoidal trajectories, with reduced overall movement.

Conclusions:

• Eigenmannia virescens likely generate an internal dynamical model to predict and improve tracking of predictable visual motion.
• This predictive tracking mechanism enhances navigation efficiency, particularly for consistent movements.
• The findings suggest that predictive modeling for stimulus motion may be a widespread mechanism across diverse taxa and behaviors, extending beyond human nonlocomotor tasks.