Locomotor efference copy signaling and gaze control: An evolutionary perspective

Area of Science:

• Neuroscience
• Comparative Physiology
• Motor Control

Background:

• Locomotion generates head/body motion that perturbs gaze.
• Vestibular sensors reactively detect motion, but feedforward mechanisms can anticipate these effects.
• Neural replicas of motor commands, or efference copies (ECs), are proposed to provide predictive signals.

Purpose of the Study:

• To investigate the role of locomotor efference copies (ECs) in gaze stabilization.
• To explore the evolutionary conservation of ECs in different vertebrate species.
• To understand the interaction between ECs and vestibular feedback in ocular motor control.

Main Methods:

• Studies in deafferented in vitro preparations (amphibian larvae) during fictive swimming.
• Electrophysiological and behavioral analyses in lamprey, frogs, and mice.
• Behavioral observations in other mammals, including humans.

Main Results:

• Direct evidence confirms locomotor ECs contribute to gaze stabilization in diverse vertebrates.
• The mechanism is conserved from ancestral lamprey to adult tetrapods (frogs, mice) and mammals.
• Behavioral evidence supports EC involvement in human gaze stabilization.
• The interplay between ECs and vestibular feedback varies with sensory ability and locomotor activity.

Conclusions:

• Locomotor efference copies are a conserved neural mechanism for gaze stabilization across vertebrates.
• ECs provide a feedforward system that complements or replaces reactive vestibular signaling.
• The findings highlight the evolutionary significance of predictive motor control for maintaining visual stability.