UC Berkeley

How animals generate stable, appropriate decisions in a noisy sensory environment is a fundamental question in neuroscience. Animals must correctly appraise the sensory world, taking into account their internal state and previous experiences. Feeding behavior in the fruit fly, Drosophila melanogaster, is an ideal model system to investigate the neural basis of decision-making. While feeding initiation in Drosophila is mostly described as the simple product of the palatability of a given substance, this behavioral decision is actually quite complex and is influenced by sensory stimuli, internal states, prior encounters, and other factors.

As with other animals, feeding behavior in the fruit fly is likely influenced by the commitment to other behaviors, as the engagement in one behavior typically suppresses the initiation of others. The first part of this thesis describes the interaction between two mutually exclusive behaviors in the fly, feeding and locomotion. This study characterizes a single pair of interneurons in the nerve cord of the fly that mediates the suppression of feeding initiation by locomotion. These neurons are activated by mechanosensory input from the legs of the fly and suppress feeding initiation through the inhibition of the proboscis extension response. This work shows that these behaviors are indeed mutually exclusive and identifies a single pair of neurons that mediates part of this interaction.

The second part of this thesis attempts to place these proboscis extension-inhibiting neurons in the larger context of the feeding circuit. Anatomical, functional, and behavioral experiments identify potential synaptic partners with these neurons as well as other, as of yet unidentified, neurons that modulate feeding initiation in the fly. This work identifies candidate neurons that influence feeding decisions in Drosophila, and provides a starting point for the characterization of neurons in the Drosophila feeding circuit.