Animals, including humans, cope with environmental change for survival and reproduction. The brain processes environmental stimuli to modify behavior. However, this ability declines along with aging. Therefore, our research is to first understand the mechanism of how a neural circuit loses its function from memory and learning to behavior during aging. Secondly, we are focusing on collective behavior. We are fascinated with the emergence of intelligent behaviors when living things such as honeybees and ants collectively self-organize at the population level. We are studying the mechanism underlying collective pattern formation.
To understand the mechanism underlying collective behavior and neural circuit aging, we have used the nematode C. elegans as a model animal. C. elegans are comprised of only 959 somatic cells, including 302 neurons. The life cycle of C. elegans is quite short, 3.5 days at 20 degrees. This is an advantage for aging research since we can better observe aging. Furthermore, the body of C. elegans is quite small, only 1 millimeter, and transparent. Owing to this feature, we can simultaneously observe molecules, cells, and behaviors, non-invasively. Therefore, C. elegans is one of the most suitable model animals for behavior and aging research.
・Deciphering the principle underlying collective behaviors
Flocks of birds, schools of fish, crowds of sheep and humans exhibit beautiful collective behaviors. Animals, including humans, collectively self-organize to increase survival and reproduction rate. However, these are mysterious phenomena. Each particle does not know its position in collectives. Why can randomly moving particles form ordered patterns even without a leader? The research field to study this mechanism is known as active matter physics.
The purpose of active matter physics is to understand the universal raw underlying collective pattern formation. Therefore, it requires both theoretical and experimental studies. The mathematical model proposed by the theoretical research should be verified by observation and perturbation of collective behavior using living animals or non-living ingredients. We recently found that C. elegans collectively form a network pattern to survive desiccation. This is the first experimental system of an animal’s collective behavior on a laboratory scale. We further controlled several parameters of this mathematical model by experiments and simulations. Finally, we found that the local nematic alignment, circular moving, and attraction forces are the key rules for C. elegans collective pattern formations (Sugi* et al. Nature Commun, 2019). We also discovered other collective behaviors and therefore are now investigating their underlying mechanisms.
・Studies on behavioral aging by whole-brain imaging technology
Aging causes the decline of sensory response-ability. Understanding its underlying mechanisms requires a systems biology approach, in which stimulus parameters are controlled and neural network responses are quantified throughout the life-course. Here, I aim to develop a whole life-course, whole-brain imaging technology to understand a mechanism underlying the age-dependent decline of mechanosensory response. I will describe a model by clarifying transfer functions and dynamical systems. The age-dependent declines of all the sensory modalities, such as temperature sensation, are critical risk factors in clinical medicines. This study will be the first step in establishing a new research field ‘sensory aging’.