"The spinal locomotor central pattern generator (CPG) generates
rhythmic activity with alternating flexion and extension phases. This
rhythmic pattern is likely to result from inhibitory interactions
between neural populations representing flexor and extensor
half-centers. However, it is unclear whether the flexor-extensor CPG
has a quasi-symmetric organization with both half-centers critically
involved in rhythm generation, features an asymmetric organization
with flexor-driven rhythmogenesis, or comprises a pair of
intrinsically rhythmic half-centers. There are experimental data that
support each of the above concepts but appear to be inconsistent with
the others. In this theoretical/modeling study, we present and analyze
a CPG model architecture that can operate in different regimes
consistent with the above three concepts depending on conditions,
which are defined by external excitatory drives to CPG
half-centers. We show that control of frequency and phase durations
within each regime depends on network dynamics, defined by the
regime-dependent expression of the half-centers' intrinsic rhythmic
capabilities and the operating phase transition mechanisms (escape
vs. release). Our study suggests state dependency in locomotor CPG
operation and proposes explanations for seemingly contradictory
experimental data."
Reference:
1 .
Ausborn J, Snyder AC, Shevtsova NA, Rybak IA, Rubin JE (2018) State-dependent rhythmogenesis and frequency control in a half-center locomotor CPG. J Neurophysiol 119:96-117 [PubMed]
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