Motivational states are the brain's way of matching our behaviors to our needs and capacities: we eat when we're hungry and sleep when we're sleepy—but we forgo food and sleep when other things seem more important. Our motivations are central to who we are, but too often they spiral out of control causing addictions and other behavior and mood disorders.

We study motivation in Drosophila melanogaster, an organism with remarkable behavioral flexibility despite its small brain. We focus on sexually dimorphic behaviors because they are controlled by neurons that we can locate using sex-specific markers. We have identified circuit elements that:

i) increase motivation with abstinence,
ii) reduce motivation with goal achievement,
iii) hold a motivational signal for days,
iv) sustain satiety for days,
v) interpret a motivational signal to adjust behavioral initiation and persistence,
vi) track time over minutes,
vii) integrate inputs from competing motivations,
viii) switch behaviors,
ix) induce fictive behaviors,
x) store memories of previous behavioral outcomes,
xi) accumulate evidence,
xii) report the outcome of network computations,
xiii) generate motor patterns, and
xiv) modulate motor patterns.

We put these elements together to form circuit diagrams and study the molecular- and circuit-level properties that give each element its specific functions. Correlates to mammalian circuit features are often very clear. Our goal is to inspire researchers in other systems to adapt our hypotheses for behavioral control, as has previously been done with early studies of molecular genetics, developmental biology, and circadian rhythms in the fly.