aggregation and bordering behaviors were measured essentially as described2 ; values report the average fraction of three or more behavioral assays of 150 animals each . average locomotion speed was calculated by tracking 20 animals for 10 minutes with an automated tracking system30 . for rmg - selective expression of transgenes , loxp - flanked lacz sequence containing a transcriptional stop , three repeated polya sequences , and two repeated mrna cleavage sequences was inserted upstream of npr-1::sl2::gfp under the control of the flp-21 promoter ( flp-21::loxstoplox::cdna(gfp , npr-1 , tetx , or pkc-1(gf ) ) . transgenic animals containing this plasmid strong and consistent expression was observed in rmg and m2 ; adl , asj , and ask were seen weakly and inconsistently . for ascaroside chemotaxis assays , washed animals were placed in the center of a 4-quadrant plate with ascarosides in alternating quadrants , and scored after ten minutes . a chemotaxis index ( c.i . ) was calculated as ( # of animals on pheromone quadrants  # of animals on buffer quadrants)/(total # of animals ) . in the cartoon in fig . 4 a cocktail of three ascarosides was used ; individual ascarosides and other combinations are in supplementary fig . calcium imaging of the aia and ask neurons was performed in a custom - fabricated microfluidic device , essentially as described26 . for ask imaging , the transgene kyex2866 was used , with gcamp2.2b ( gift from loren looger ) expressed under the sra-9 promoter . for aia imaging , ask fluorescence was recorded in the neuronal cell body , and aia fluorescence was measured in the dorsal aia process in the nerve ring .
innate social behaviors emerge from neuronal circuits that interpret sensory information based on an individual 's own genotype , sex , and experience . 
 the regulated aggregation behavior of c. elegans , a simple animal with only 302 neurons , is an attractive system to analyze these circuits . 
 wild social strains of the nematode caenorhabditis elegans aggregate in the presence of specific sensory cues , but solitary strains do not1,2,3,4 . here 
 we identify the rmg inter / motor neuron as the hub of a regulated circuit that controls aggregation and related behaviors . 
 rmg is the central site of action of the neuropeptide receptor gene npr-1 , which distinguishes solitary strains ( high npr-1 activity ) from wild social strains ( low npr-1 activity ) ; high rmg activity is essential for all aspects of social behavior . 
 anatomical gap junctions connect rmg to multiple classes of sensory neurons known to promote aggregation , and to ask sensory neurons , which are implicated in male attraction to hermaphrodite pheromones5 . 
 we find that ask neurons respond directly to pheromones , and that high rmg activity enhances ask responses in social strains , causing hermaphrodite attraction to pheromones at concentrations that repel solitary hermaphrodites . 
 the coordination of social behaviors by rmg suggests an anatomical hub - and - spoke model for sensory integration in aggregation , and points to functions for related circuit motifs in the c. elegans wiring diagram .