Behavioral probabilities and sample videos for "Behavioral evidence for nested central pattern generator control of Drosophila grooming"

Central pattern generators (CPGs) are neurons or neural circuits that
produce periodic output without requiring patterned input. More complex
behaviors can be assembled from simpler subroutines, and nested CPGs have
been proposed to coordinate their repetitive elements, organizing control
over different time-scales. Here, we use behavioral experiments to
establish that Drosophila grooming may be controlled by nested CPGs. On a
short time-scale (5-7 Hz), flies execute periodic leg sweeps and rubs.
More surprisingly, transitions between bouts of head cleaning and leg
rubbing are also periodic on a longer time-scale (0.3 - 0.6 Hz). We
examine grooming at a range of temperatures to show that the frequencies
of both oscillations increase – a hallmark of CPG control – and also that
the two time-scales increase at the same rate, indicating that the nested
CPGs may be linked. This relationship also holds when sensory drive is
held constant using optogenetic activation, but the rhythms can decouple
in spontaneously grooming flies, showing that alternative control modes
are possible. Loss of sensory feedback does not disrupt periodicity but
slows the longer time-scale alternation. Nested CPGs simplify generation
of complex but repetitive behaviors, and identifying them in Drosophila
grooming presents an opportunity to map the neural circuits that
constitute them.