Abstract
We analyzed the effects of dopamine signaling on the temporal organization of rest and activity in Drosophila melanogaster. Locomotor behaviors were recorded using a video-monitoring system, and the amounts of movements were quantified by using an image processing program. We, first, confirmed that rest bout durations followed long-tailed (i.e., power-law) distributions, whereas activity bout durations did not with a strict method described by Clauset et al. We also studied the effects of circadian rhythm and ambient temperature on rest bouts and activity bouts. The fraction of activity significantly increased during subjective day and at high temperature, but the power-law exponent of the rest bout distribution was not affected. The reduction in rest was realized by reduction in long rest bouts. The distribution of activity bouts did not change drastically under the above mentioned conditions. We then assessed the effects of dopamine. The distribution of rest bouts became less long-tailed and the time spent in activity significantly increased after the augmentation of dopamine signaling. Administration of a dopamine biosynthesis inhibitor yielded the opposite effects. However, the distribution of activity bouts did not contribute to the changes. These results suggest that the modulation of locomotor behavior by dopamine is predominantly controlled by changing the duration of rest bouts, rather than the duration of activity bouts.
Highlights
Human behavior is highly diverse and profoundly complex
We found that dopamine modulates the rest length without perturbation of the temporal organization of locomotor activity When the total amount of activity per day is modulated, the modulation occurs through the changes in the number of activity episodes but not their length
We separately analyzed the temporal structure of rest and activity bouts
Summary
Human behavior is highly diverse and profoundly complex. Our decisions are influenced by both our internal drive and our perception of environments. Recent studies have shown that many human behaviors have shared common characteristics in the temporal organization. Interevent intervals of social behaviors such as e-mail communications and trade transactions follow power-law distributions [1]. How rest and activity episodes are interwoven in behaving animals was studied recently [2,3], indicating that rest bouts follow the powerlaw distribution in both human and mice, whereas activity bouts follow the exponential distribution. Nakamura et al, reported that patients with major depressive disorder exhibited decrease of scaling exponent in power-law distribution of resting period, suggesting novel quantitative strategy for neuropsychiatry [3]. Power-law distributions are abundant in various natural phenomena and do not indicate the universality of animal behaviors by themselves, the biological mechanism underlying the power law distributions attracts attentions and remains an open question
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