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Neural control of limb coordination. II. Hatching and walking motor output patterns in the absence of input from the
A Bekoff1, J A Kauer, A Fulstone
1Department of Environmental, Population and Organismic Biology, University of Colorado, Boulder 80309.
Insights
Spinal cord circuitry in young chicks can produce complex leg movements for walking and hatching without brain input. This research demonstrates the intrinsic capabilities of the spinal cord for motor pattern generation.
Area of Science:
- Neuroscience
- Developmental Biology
- Motor Control
Background:
- The brain typically initiates and modulates complex motor behaviors like walking and hatching.
- Understanding the role of spinal circuitry in generating these patterns independently is crucial for developmental neuroscience.
Purpose of the Study:
- To investigate if spinal cord circuitry alone can produce the distinct leg motor patterns of walking and hatching in posthatching chicks.
- To determine the extent to which these motor patterns are maintained after removing descending brain input.
Main Methods:
- Cervical spinal cord transection was performed on 0- to 3-day old chicks.
- Locomotor behaviors (walking, hatching) were elicited using treadmill stimulation, sensory stimulation (pinch), and specific positioning.
- Electromyography (EMG) recordings from six leg muscles were quantitatively analyzed.
Main Results:
- Spinal chicks exhibited walking with weight support on a treadmill and hatching-like leg movements.
- EMG analysis revealed that characteristic bursting patterns and phase relationships in leg muscles were preserved.
- Key features of walking and hatching motor patterns, including burst duration and cycle period relationships, were maintained in the absence of brain input.
Conclusions:
- Spinal cord circuitry in young chicks possesses the intrinsic capacity to generate fundamental aspects of walking and hatching motor patterns.
- Descending input from the brain is not essential for producing the core features of these behaviors, although some modifications may occur.
Abstract:
This study examines the effect of removing input descending from the brain on the production of the distinctive leg motor patterns of walking and hatching by spinal circuitry of 0- to 3-day old posthatching chicks. Transection of the cervical spinal cord was performed and chicks were tested between 2 and 28 h after surgery. Walking with good weight support could be elicited from many spinal chicks when placed on a moving treadmill belt. In some cases, sensory stimulation resulting from tail and/or wing pinch was also used. Placing spinal chicks in the hatching position in glass eggs was sufficient to elicit hatching-like leg movements in some animals. Wing pinch was used to elicit more or longer episodes of leg movements. Quantitative analyses of EMG recordings from 6 leg muscles were used to evaluate the changes in motor patterns after cervical spinal transection. Most of the characteristic features of walking and hatching are maintained after descending input from the brain is eliminated. Each muscle is activated in the double or single bursting pattern typical of the normal behavior. Characteristic phase relationships are also preserved. In addition, burst duration versus cycle period relationships seen during the normal behaviors are maintained in the spinal animals. This shows that circuitry located in the spinal cord can produce these distinctive aspects of the hatching and walking motor patterns in the absence of brain input. While many features of walking and hatching patterns were maintained in spinal animals, some changes were noted.(ABSTRACT TRUNCATED AT 250 WORDS)