Trends affecting the analysis of adult locomotion. Behavior of a consistently behaving wild-type fly (top row) was compared to that of a wild-type adult that displayed decreasing activity toward the end of the behavioral record (bottom row). Locomotor activity was monitored in constant darkness, as indicated by shading throughout the actograms in the left-most column. Within each actogram, a given row shows two consecutive days of activity; the second such day is re-plotted in the left half of the next row down (thus, consecutive days of locomotion can be viewed both horizontally and vertically); heights of bars within a given actogram row reflect varying amounts of locomotion per half-hour data-collection bin. Note the white bar on day 15 in both actograms, which indicates that the data collection system crashed and rebooted. In the column second from the left, the locomotor data are re plotted as counts vs. time, This presentation reveals that the fly whose behavior is shown (and analyzed) in the bottom row became less active between days 9 12. The third column from the left shows the autocorrelation plot for these behavioral records, which indicate rhythmicity in the data; but the correlogram at the bottom is relatively irregular, with its wandering baseline compared to the one in the top row – a reflection of the "signal decline" in the corresponding locomotor record (bottom row). In the rightmost column, the MESA plots also reflect this behavioral difference, in that there is increased spectral density for relatively high abscissa values in the bottom plot compared with the spectral result in the top row. These features of the analytical results (in the right half of the figure) resonate with the long-term trend exhibited by the bottom-row fly vis a vis the top one.