Mathematical monotsukuri: Summing a constant may help to detect synchronized brain activity -- ScienceDaily
Humans are good at detecting whether separate things happen simultaneously, for example, if two lights flash together or not. When two swings move with a regular motion, it is easy to tell whether there is any temporal relationship or "synchronization." However, the trajectory of some objects, such as kites, can be very complicated but still exhibit some pattern, even though our eyes may fail to follow it; such systems are called "chaotic." In physics, chaos does not mean lack of order; it indicates the presence of a very complicated type of order. Such situations can be found across very different scenarios, including the activity of neurons.
When trajectories, which do not necessarily correspond to physical movement and can instead represent electrical signals, are sufficiently complicated, it becomes challenging to determine if they are synchronized. In many cases, only some aspects of their motion might be interrelated. Hence, measuring synchronization is difficult and has been the subject of research for decades.