• Version [version]
• Download 2582
• File Size 3.61 MB
• File Count 1
• Create Date April 17, 2015
• Last Updated April 17, 2015

Identification of neural circuits required for spontaneous behavioral variability

Even in the absence of external stimuli, brains are capable of initiating spontaneous actions. Spontaneous turning attempts (yaw torque) initiated by Drosophila fruit flies tethered at the torque meter, are not completely governed by random noise in the brain but generated and controlled by intrinsic circuits (Maye et al. 2007). This conclusion is based, among other analyses, on nonlinear forecasting analyses (S-Map procedure) detecting a nonlinear signature in the temporal structure of the torque data. However, nothing is known about the underlying circuits and the neurobiological mechanisms for generating spontaneous actions.

We used the Gal4/UAS system to silence candidate neural circuits in the fly brain, by expressing tetanus toxin light chain (TNT-E) to prevent synaptic vesicle fusion. Yaw turning behavior of tethered flies was recorded with the wingbeat analyzer; the environment of the fly was kept spatially homogeneous and temporally constant, preventing the fly from perceiving any stimuli which might elicit turning behavior. Candidate lines expressing mainly in the central complex and mushroom-bodies were measured. S-Map analysis suggests a defined subset of central complex neurons to be involved in generating spontaneous behavior, while the mushroom-bodies seem not to play any role. Computing the power spectrum of the yaw torque signal from each candidate line revealed that the S-Map phenotype is not due to irregular oscillatory behavior. Automated detection of yaw torque spikes (the equivalent of body-saccades in free flight) did not reveal any significant difference from control strains in the affected candidate lines, suggesting that the general behavioral repertoire of turning behavior is unaffected by the TNT-E expression.