Abstract
Actograms are well-established methods used for visualizing periodic activity of animals in chronobiological research. They help in the understanding of the overall characteristics of rhythms and are instrumental in defining the direction of subsequent detailed analysis. Although there exists specialized software for creating actograms, new users such as students and researchers from other fields often find it inconvenient to use. In this study, we demonstrate a fast and easy method to create actograms using Microsoft Excel. As operations in Excel are simple and user-friendly, it takes only a few minutes to create an actogram. Using this method, it is possible to obtain a visual understanding of the characteristics of rhythms not only from typical activity data, but also from any kind of time-series data such as body temperature, blood sugar level, gene expressions, sleep electroencephalogram, heartbeat, and so on. The actogram thus created can also be converted to the "heatogram” shown by color temperature. As opposed to conventional chronograms, this new type of chronogram facilitates easy understanding of rhythmic features in a more intuitive manner. This method is therefore convenient and beneficial for a broad range of researchers including students as it aids in the better understanding of periodic phenomena from a large amount of time-series data.
Highlights
There are many rhythmic events in living organisms [1]
A typical example is the circadian rhythm, which is the approximately 24-hour activity rhythm found in numerous animals and plants as well as some bacteria
We describe a protocol that converts the activity rhythm of a mouse acquired by an infrared sensor into a conventional actogram (3.1), and a protocol that expresses it as color temperature in the form of a heatmap (3.2)
Summary
There are many rhythmic events in living organisms [1]. A typical example is the circadian rhythm, which is the approximately 24-hour activity rhythm found in numerous animals and plants as well as some bacteria. In the field of chronobiological research, activity patterns such as circadian rhythms and circatidal rhythms are often represented using actograms. Actograms are created using professional software, which is often packaged with the behavior analysis system of animals, such as ClockLab (Actimetrics) and Chronobiology kit Software Systems) or free software provided by chronobiologists [3,4,5] While these various software packages provide advanced analysis tools, they are often inconvenient for new users such as students and researchers in other research fields. Many researchers including students routinely use Excel for their data analysis. If the data can be represented in a visual manner with the function of Excel, it is easy to understand and operate the actograms. If further analysis of rhythmic characteristics is required, free software solutions such as Actogram J [3] and RhythmicAlly [5] may be useful
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