Journal of Neuroscience, Vol 7, 2320-2330, Copyright © 1987 by Society for Neuroscience
Neural control of limb coordination. I. Comparison of hatching and walking motor output patterns in normal and deafferented chicks
A Bekoff, MP Nusbaum, AL Sabichi and M Clifford
Previous work has shown that the neural circuits underlying the leg
movements of walking and hatching coexist in post-hatching chicks (Bekoff
and Kauer, 1984). In the present study, quantitative analysis of leg EMGs
shows that there are some similarities, but also significant differences,
in the motor output patterns of walking and hatching. This study examines
the effect of removing sensory feedback from the legs on the production of
the distinctive leg motor patterns. The temporal characteristics and
interlimb coordination of hatching and walking are little affected.
However, major changes in intralimb motor output patterns are seen when
compared to records from normal chicks. These changes fall into one of 2
categories. Some parameters show similar changes in both behaviors after
deafferentation (e.g., increases in flexor burst durations and cycle
period). This suggests that certain features of sensory input from the legs
normally modulate the hatching and walking pattern-generating circuitry in
similar ways. Other parameters show convergence. That is, these aspects of
the 2 intralimb motor patterns become more similar to each other after
removal of sensory input. This is consistent with the hypothesis that some
feature of sensory input from the legs normally modulates one set of
multiuse intralimb circuitry to produce different output patterns. In
general, the walking pattern becomes more like hatching after
deafferentation, rather than the reverse, which suggests that the hatching
pattern is a more basic one. The maintenance of some residual differences
in intralimb motor patterns after leg deafferentation suggests that other
sources of modulation must also be involved, or that there are some
additional elements of circuitry that are called into play during the
normal production of walking and hatching.