Cross connections among crayfish claw efferents

Spontaneous and reflex spike trains in the efferent neurons to the claw opener and closer muscles of the crayfish were cross correlated. The opener inhibitor and the slow closer excitor were found to be closely synchronized under all conditions. Details of the correlation suggested an electrical synapse coordinating these neurons, possibly bidirectional, but possibly from CE to OI only. The OE-OI cross correlogram showed signs of direct central inhibition of OE to OI. Polysynaptic inhibition of OI by OE may also occur. CI and OI show signs of mutual inhibition. An unidentified closer bundle efferent was strongly and positively correlated with OE. The results are consistent with the respective muscular effects of the pairs of neurons involved; they disagree, however, with some previous findings (19).