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Updated: May 5, 2026
Chicken Recombinant Limbs Assay to Understand Morphogenesis, Patterning, and Early Steps in Cell Differentiation
Published on: January 12, 2022
Spontaneous locomotor activity in late-stage chicken embryos is modified by stretch of leg muscles
Nina S Bradley1, Young U Ryu, Marie C Yeseta
1University of Southern California, Department of Biokinesiology and Physical Therapy, 1540 E. Alcazar Street, Center for Health Professions 155, Los Angeles, CA 90033-9006, USA.
Insights
Proprioception circuits in chick embryos detect muscle length changes days before hatching. This sensory feedback is crucial for developing precocious walking skills and adaptive locomotion after hatching.
Area of Science:
- Developmental neuroscience
- Motor control
- Embryology
Background:
- Chicks exhibit advanced motor skills before hatching and shortly after birth.
- The precise mechanisms underlying the development of these precocious walking abilities remain unclear.
- Understanding proprioception's role is key to explaining early motor skill acquisition.
Purpose of the Study:
- Investigate if environmental interactions and pre-hatching movement influence precocious motor skills.
- Determine when proprioception circuits in chick embryos can process muscle length variations.
- Assess if proprioception circuits modulate leg muscle activity during embryonic stepping movements.
Main Methods:
- Recorded leg muscle activity and kinematics in chick embryos.
- Utilized an ankle restraint to induce atypical limb posture.
- Compared leg muscle activity during spontaneous repetitive limb movements (RLMs) in control and restrained embryos.
Main Results:
- Proprioceptors were found to detect muscle length/tension changes starting 3 days before hatching.
- Ankle restraint led to autogenic excitation of ankle flexors and reciprocal inhibition of ankle extensors.
- Knee extensor activity during RLMs was altered by restraint 1 day before hatching.
Conclusions:
- Proprioceptive sensory feedback is functional in chick embryos days before hatching.
- Proprioception likely plays a significant role in the development of precocious locomotor skills.
- These findings suggest proprioceptive system maturation contributes to adaptive locomotion at hatching.
Abstract:
Chicks initiate bilateral alternating steps several days before hatching and adaptively walk within hours of hatching, but emergence of precocious walking skills is not well understood. One of our aims was to determine whether interactions between environment and movement experience prior to hatching are instrumental in establishing precocious motor skills. However, physiological evidence of proprioceptor development in the chick has yet to be established; thus, one goal of this study was to determine when in embryogenesis proprioception circuits can code changes in muscle length. A second goal was to determine whether proprioception circuits can modulate leg muscle activity during repetitive limb movements for stepping (RLMs). We hypothesized that proprioception circuits code changes in muscle length and/or tension, and modulate locomotor circuits producing RLMs in anticipation of adaptive locomotion at hatching. To this end, leg muscle activity and kinematics were recorded in embryos during normal posture and after fitting one ankle with a restraint that supported the limb in an atypical posture. We tested the hypotheses by comparing leg muscle activity during spontaneous RLMs in control posture and ankle extension restraint. The results indicated that proprioceptors detect changes in muscle length and/or muscle tension 3 days before hatching. Ankle extension restraint produced autogenic excitation of the ankle flexor and reciprocal inhibition of the ankle extensor. Restraint also modified knee extensor activity during RLMs 1 day before hatching. We consider the strengths and limitations of these results and propose that proprioception contributes to precocious locomotor development during the final 3 days before hatching.
