Limits...
A mathematical model provides mechanistic links to temporal patterns in Drosophila daily activity.

Lazopulo A, Syed S - BMC Neurosci (2016)

Bottom Line: In the time domain, we find the timescales of the exponentials in our model to be ~1.5 h(-1) on average.Our results indicate that multiple spectral peaks from fly locomotion are simply harmonics of the circadian period rather than independent ultradian oscillators as previously reported.From timescales of the exponentials we hypothesize that model rates reflect activity of the neuropeptides that likely transduce signals of the circadian clock and the sleep-wake homeostat to shape behavioral outputs.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of Miami, 1320 Campo Sano Avenue, Coral Gables, FL, 33146, USA.

ABSTRACT

Background: Circadian clocks are endogenous biochemical oscillators that control daily behavioral rhythms in all living organisms. In fruit fly, the circadian rhythms are typically studied using power spectra of multiday behavioral recordings. Despite decades of study, a quantitative understanding of the temporal shape of Drosophila locomotor rhythms is missing. Locomotor recordings have been used mostly to extract the period of the circadian clock, leaving these data-rich time series largely underutilized. The power spectra of Drosophila and mouse locomotion often show multiple peaks in addition to the expected at T ~ 24 h. Several theoretical and experimental studies have previously used these data to examine interactions between the circadian and other endogenous rhythms, in some cases, attributing peaks in the T < 24 h regime to ultradian oscillators. However, the analysis of fly locomotion was typically performed without considering the shape of time series, while the shape of the signal plays important role in its power spectrum. To account for locomotion patterns in circadian studies we construct a mathematical model of fly activity. Our model allows careful analysis of the temporal shape of behavioral recordings and can provide important information about biochemical mechanisms that control fly activity.

Results: Here we propose a mathematical model with four exponential terms and a single period of oscillation that closely reproduces the shape of the locomotor data in both time and frequency domains. Using our model, we reexamine interactions between the circadian and other endogenous rhythms and show that the proposed single-period waveform is sufficient to explain the position and height of >88 % of spectral peaks in the locomotion of wild-type and circadian mutants of Drosophila. In the time domain, we find the timescales of the exponentials in our model to be ~1.5 h(-1) on average.

Conclusions: Our results indicate that multiple spectral peaks from fly locomotion are simply harmonics of the circadian period rather than independent ultradian oscillators as previously reported. From timescales of the exponentials we hypothesize that model rates reflect activity of the neuropeptides that likely transduce signals of the circadian clock and the sleep-wake homeostat to shape behavioral outputs.

No MeSH data available.


Comparison of data (left) to the model (right). a Average recording of 14 wild type flies measured in LD for 5 days; day/night shown with white/black bars. Model consists of four exponential terms with rates , , , and widths of morning and evening peaks given by  and . b Autocorrelations of data and model with primary period 24 h. Periods in signal are found from regularly appearing peaks with high correlation. Peaks exceeding the dashed line, where N is number of data points in activity trace, represent strong correlations. Strong 24 and 12 h periods are seen in both graphs. c Lomb–Scargle power spectra for the data and the model. Model reproduces strong peaks as well as small side peaks (arrows), which are from the Dirichlet kernel (see Additional file 1). Parameters used for this simulation:
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4835852&req=5

Fig2: Comparison of data (left) to the model (right). a Average recording of 14 wild type flies measured in LD for 5 days; day/night shown with white/black bars. Model consists of four exponential terms with rates , , , and widths of morning and evening peaks given by and . b Autocorrelations of data and model with primary period 24 h. Periods in signal are found from regularly appearing peaks with high correlation. Peaks exceeding the dashed line, where N is number of data points in activity trace, represent strong correlations. Strong 24 and 12 h periods are seen in both graphs. c Lomb–Scargle power spectra for the data and the model. Model reproduces strong peaks as well as small side peaks (arrows), which are from the Dirichlet kernel (see Additional file 1). Parameters used for this simulation:

Mentions: Figure 2a shows population averaged fly activity obtained from measurement of 14 flies in simulated light–dark conditions (LD) for 5 days. Drosophila daily activity has two distinguishable peaks. The morning peak (M) starts during the night and has a maximum when the light turns on and the evening peak (E) starts during the day and has a maximum when the light turns off. We constructed a model with a single fundamental period which reproduces these features of the activity. Our model consists of four normalized exponential terms with rates , with subscripts denoting morning decay (MD), morning rise (MR), evening decay (ED) and evening rise (ER):Fig. 2


A mathematical model provides mechanistic links to temporal patterns in Drosophila daily activity.

Lazopulo A, Syed S - BMC Neurosci (2016)

Comparison of data (left) to the model (right). a Average recording of 14 wild type flies measured in LD for 5 days; day/night shown with white/black bars. Model consists of four exponential terms with rates , , , and widths of morning and evening peaks given by  and . b Autocorrelations of data and model with primary period 24 h. Periods in signal are found from regularly appearing peaks with high correlation. Peaks exceeding the dashed line, where N is number of data points in activity trace, represent strong correlations. Strong 24 and 12 h periods are seen in both graphs. c Lomb–Scargle power spectra for the data and the model. Model reproduces strong peaks as well as small side peaks (arrows), which are from the Dirichlet kernel (see Additional file 1). Parameters used for this simulation:
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4835852&req=5

Fig2: Comparison of data (left) to the model (right). a Average recording of 14 wild type flies measured in LD for 5 days; day/night shown with white/black bars. Model consists of four exponential terms with rates , , , and widths of morning and evening peaks given by and . b Autocorrelations of data and model with primary period 24 h. Periods in signal are found from regularly appearing peaks with high correlation. Peaks exceeding the dashed line, where N is number of data points in activity trace, represent strong correlations. Strong 24 and 12 h periods are seen in both graphs. c Lomb–Scargle power spectra for the data and the model. Model reproduces strong peaks as well as small side peaks (arrows), which are from the Dirichlet kernel (see Additional file 1). Parameters used for this simulation:
Mentions: Figure 2a shows population averaged fly activity obtained from measurement of 14 flies in simulated light–dark conditions (LD) for 5 days. Drosophila daily activity has two distinguishable peaks. The morning peak (M) starts during the night and has a maximum when the light turns on and the evening peak (E) starts during the day and has a maximum when the light turns off. We constructed a model with a single fundamental period which reproduces these features of the activity. Our model consists of four normalized exponential terms with rates , with subscripts denoting morning decay (MD), morning rise (MR), evening decay (ED) and evening rise (ER):Fig. 2

Bottom Line: In the time domain, we find the timescales of the exponentials in our model to be ~1.5 h(-1) on average.Our results indicate that multiple spectral peaks from fly locomotion are simply harmonics of the circadian period rather than independent ultradian oscillators as previously reported.From timescales of the exponentials we hypothesize that model rates reflect activity of the neuropeptides that likely transduce signals of the circadian clock and the sleep-wake homeostat to shape behavioral outputs.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, University of Miami, 1320 Campo Sano Avenue, Coral Gables, FL, 33146, USA.

ABSTRACT

Background: Circadian clocks are endogenous biochemical oscillators that control daily behavioral rhythms in all living organisms. In fruit fly, the circadian rhythms are typically studied using power spectra of multiday behavioral recordings. Despite decades of study, a quantitative understanding of the temporal shape of Drosophila locomotor rhythms is missing. Locomotor recordings have been used mostly to extract the period of the circadian clock, leaving these data-rich time series largely underutilized. The power spectra of Drosophila and mouse locomotion often show multiple peaks in addition to the expected at T ~ 24 h. Several theoretical and experimental studies have previously used these data to examine interactions between the circadian and other endogenous rhythms, in some cases, attributing peaks in the T < 24 h regime to ultradian oscillators. However, the analysis of fly locomotion was typically performed without considering the shape of time series, while the shape of the signal plays important role in its power spectrum. To account for locomotion patterns in circadian studies we construct a mathematical model of fly activity. Our model allows careful analysis of the temporal shape of behavioral recordings and can provide important information about biochemical mechanisms that control fly activity.

Results: Here we propose a mathematical model with four exponential terms and a single period of oscillation that closely reproduces the shape of the locomotor data in both time and frequency domains. Using our model, we reexamine interactions between the circadian and other endogenous rhythms and show that the proposed single-period waveform is sufficient to explain the position and height of >88 % of spectral peaks in the locomotion of wild-type and circadian mutants of Drosophila. In the time domain, we find the timescales of the exponentials in our model to be ~1.5 h(-1) on average.

Conclusions: Our results indicate that multiple spectral peaks from fly locomotion are simply harmonics of the circadian period rather than independent ultradian oscillators as previously reported. From timescales of the exponentials we hypothesize that model rates reflect activity of the neuropeptides that likely transduce signals of the circadian clock and the sleep-wake homeostat to shape behavioral outputs.

No MeSH data available.