Modular organization of turtle spinal interneurons during normal and deletion fictive rostral scratching

Paul S.G. Stein, Susan Daniels-McQueen

Research output: Contribution to journalArticlepeer-review

53 Scopus citations


During normal rostral scratching in the spinal turtle, there is rhythmic alternation between hip-flexor and hip-extensor motor activity. During rostral scratching with hip-extensor deletions, there are successive bursts of hip-flexor motor activity and no activity in hip-extensor motor neurons. We characterized the ON- and OFF-phases of 72 descending propriospinal interneurons with distinct activity bursts during normal rostral scratching. We also studied the activity of these interneurons during deletion scratching. Hip-extensor interneurons were active when hip-flexor motor neurons were quiet in normal scratching and had zero overlap with hip-flexor motor activity. This population of hip-extensor interneurons, termed the hip-extensor module or hip-extensor unit-burst generator, was mainly quiet during deletion scratching. Our observation supports the concept that a module is a neuronal population that may be active or quiet in a coordinated manner during a spinal motor rhythm. During normal scratching, hip-flexor interneurons were active during hip-flexor motor activity, and spanning interneurons were active during both hip-flexor motor activity and quiescence. Hip-flexor and spanning interneurons with intermediate overlap with hip-flexor motor activity fired in bursts during deletion scratching. Hip-flexor and spanning interneurons with large overlap with hip-flexor motor activity fired continuously during deletion scratching. Key features of hip-flexor and spanning interneuron firing during normal scratching were preserved during deletion scratching. Thus these features do not require activity in the hip-extensor module in every cycle of a motor rhythm.

Original languageEnglish
Pages (from-to)6800-6809
Number of pages10
JournalJournal of Neuroscience
Issue number15
StatePublished - Aug 1 2002


  • Central pattern generator
  • Fictive motor patterns
  • Half-center
  • Reciprocal inhibition
  • Scratch reflex
  • Spinal cord
  • Turtle


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