Of Mice and Men — Universality and Breakdown of Behavioral Organization

Abstract

Mental or cognitive brain functions, and the effect on them of abnormal psychiatric diseases, are difficult to approach through molecular biological techniques due to the lack of appropriate assay systems with objective measures. We therefore study laws of behavioral organization, specifically how resting and active periods are interwoven throughout daily life, using objective criteria, and first discover that identical laws hold both for healthy humans subject to the full complexity of daily life, and wild-type mice subject to maximum environmental constraints. We find that active period durations with physical activity counts successively above a predefined threshold, when rescaled with individual means, follow a universal stretched exponential (gamma-type) cumulative distribution, while resting period durations below the threshold obey a universal power-law cumulative distribution with identical parameter values for both of the mammalian species. Further, by analyzing the behavioral organization of mice with a circadian clock gene (Period2) eliminated, and humans suffering from major depressive disorders, we find significantly lower parameter values (power-law scaling exponents) for the resting period durations in both these cases. Such a universality and breakdown of the behavioral organization of mice and humans, revealed through objective measures, is expected to facilitate the understanding of the molecular basis of the pathophysiology of neurobehavioral diseases, including depression, and lay the foundations for formulating a range of neuropsychiatric behavioral disorder models.

Unraveling the fluctuations of animal motor activity

“…Let us note that for human ͑arm͒ motor activity data, instead of two exponentials, a stretched exponential fit was reported. 7,9 Meanwhile, quiescence intervals are also power law distributed with exponent . Because motion intervals are in average much shorter than quiet ones, then, the statistics of interevent times is mainly dominated by that of immobility periods, in particular, sharing the same power-law decay.…”

“…This can be done by analyzing more elementary processes such as records of longterm spontaneous motor activity of laboratory animals, as recently reported in mice experiments. 9 In the present work, the activity of rats was recorded during several days. Each, even minute, movement of the animal was detected and the experimental data series analyzed from the perspective of a point process.…”

“…The simplest example probably is the temporal spacing between -even inconsequential-motor activities, which appears to be scale-free. [6][7][8][9] Despite these recent efforts the mechanisms behind such statistical behavior are not understood yet. This lack of plausible models calls for alternatives which can be helpful to identify the mechanisms at work.…”

Interpersonal Coevolution of Body Movements in Daily Face-to-Face Communication

“…Nakamura et al investigated daily body movements of healthy people and patients with a major depression using accelerometers [41], [42]. They found a universal distribution of periods of high and low body movements.…”

“…We focused on upper-body movements of people because this is also the focus in the field of daily human behavior on different time scales [10], [11], [41], [42]. We calculated the amount of upper-body movements by the same procedure as in the previous study [12].…”