These studies suggest that behavioral exclusivity can be achieved by distributed networks, but the generality of these findings remains to be explored. Feeding decisions in the vinegar fly, Drosophila melanogaster, afford an excellent opportunity to examine the hierarchy of behavioral decisions in a genetically tractable model. The relative simplicity of the fly brain with 100,000 neurons, as well as the molecular genetic approaches available in the fly to selectively manipulate identified neurons and examine the effect on animal behavior, provides a powerful platform to study the neural basis of behavioral exclusivity. In Drosophila, feeding behavior begins with detection of taste

compounds on the legs or proboscis, resulting Kinase Inhibitor Library chemical structure in proboscis extension and feeding initiation ( Edgecomb et al., 1994). Vorinostat research buy The probability that an animal performs the proboscis extension response (PER) is influenced by the palatability of the taste compound, the energy requirements of the animal, and previous associations ( Dethier,

1976, Inagaki et al., 2012, Marella et al., 2012 and Masek and Scott, 2010). The neural circuits for proboscis extension and feeding are just beginning to be elucidated. Chemosensory neurons on the legs, proboscis, and mouthparts are modality selective, detecting sugars, bitter compounds, water, or pheromones (Cameron et al., 2010, Chen et al., 2010, 17-DMAG (Alvespimycin) HCl Lu et al., 2012, Marella et al., 2006, Thistle et al., 2012 and Thorne et al., 2004; Toda et al., 2012 and Wang et al., 2004). Sensory neurons from the legs project to the ventral nerve cord (VNC) and subesophageal ganglion (SOG) of the fly brain whereas those from the proboscis and mouthparts project to the SOG (Stocker, 1994 and Wang et al., 2004). Motor neurons that drive proboscis extension as well as modulatory neurons that influence proboscis extension are also found in the SOG (Gordon and Scott, 2009, Manzo et al., 2012, Marella et al., 2012 and Rajashekhar and Singh, 1994), suggesting that the SOG

contains local circuits that process gustatory cues from detection to behavior. Whether the circuits that control proboscis extension are influenced by other behaviors or influence the probability of other behaviors has not been examined. Here, we describe a pair of interneurons in Drosophila that is activated upon stimulation of mechanosensory neurons and inhibits feeding initiation, suggesting that these neurons suppress feeding while the animal is walking. Conversely, when the neurons are inhibited, the animal continuously engages in feeding initiation at the expense of locomotion. Thus, our studies suggest that feeding initiation and locomotion are mutually exclusive behaviors and identify neurons that participate in the coordination of this behavioral choice.