title: Estimation of the size and directional output of functional groups of interneurons underlying abdominal positioning behaviors in crayfish.
abstract: Quantitative studies were made of a large population of interneurons that controls postural flexion and extension of the crayfish abdomen. The number of interneurons needed to produce a motor program was estimated by stimulating a single abdominal positioning interneuron and recording interneuronal activity that was evoked from rostral and caudal connectives in an isolated abdominal nerve cord. We also examined the role that these functional groups have in producing a stronger motor output in either a rostral or caudal direction and thus specifying various abdominal geometrics. The average number of interneurons responding to stimulation of a single abdominal positioning interneuron was 32 (range: 3-50; n = 27). The average number of interneurons that decreased activity was 10 (range: 2-32). Of 653 activated interneurons from 20 preparations, approximately 43% fired between 2 and 5 Hz, 33% fired between 6 and 15 Hz, and 25% fired > 15 Hz. The size of a recruited group was usually but not always correlated with the strength of its motor response or with the direction of motor bias. Therefore, the contribution of a group may depend upon the number of active elements as well as synaptic efficacy.
authors.affiliation: Department of Zoology, University of Texas at Austin 78712, USA.
authors.forename: L D
authors.initials: LD
authors.lastname: Brewer
authors.forename: J L
authors.initials: JL
authors.lastname: Larimer
mesh_terms: D000005:Abdomen / Q000294:innervation*; D000200:Action Potentials; D000818:Animals; D003400:Astacoidea / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D017952:Ganglia, Invertebrate / Q000502:physiology; D007395:Interneurons / Q000166:cytology / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology