Common motor mechanisms support body load in serially homologous legs of cockroaches in posture and walking |
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Authors: | Laura A Quimby Ayman S Amer Sasha N Zill |
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Institution: | (1) Department of Anatomy, Cell and Neurobiology, Marshall University School of Medicine, Huntington, WV 25704, USA |
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Abstract: | We studied the mechanisms underlying support of body load in posture and walking in serially homologous legs of cockroaches.
Activities of the trochanteral extensor muscle in the front or middle legs were recorded neurographically while animals were
videotaped. Body load was increased via magnets attached to the thorax and varied through a coil below the substrate. In posture,
tonic firing of the slow trochanteral extensor motoneuron (Ds) in each leg was strongly modulated by changing body load. Rapid
load increases produced decreases in body height and sharp increments in extensor firing. The peak of extensor activity more
closely approximated the maximum velocity of body displacement than the body position. In walking, extensor bursts in front
and middle legs were initiated during swing and continued into the stance phase. Moderate tonic increases in body load elicited
similar, specific, phase dependent changes in both legs: extensor firing was not altered in swing but was higher after foot
placement in stance. These motor adjustments to load are not anticipatory but apparently depend upon sensory feedback. These
data are consistent with previous findings in the hind legs and support the idea that body load is countered by common motor
mechanisms in serially homologous legs. |
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Keywords: | Load Trochanteral extensor muscle Posture Walking Homology |
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