  Metastability, characterized by a variability of regimes in time, is a
ubiquitous type of neural dynamics. It has been formulated in many different
ways in the neuroscience literature, however, which may cause some confusion.
In this Perspective, we discuss metastability from the point of view of
dynamical systems theory. We extract from the literature a very simple but
general definition through the concept of metastable regimes as long-lived but
transient epochs of activity with unique dynamical properties. This definition
serves as an umbrella term that encompasses formulations from other works, and
readily connects to concepts from dynamical systems theory. This allows us to
examine general dynamical properties of metastable regimes, propose in a
didactic manner several dynamics-based mechanisms that generate them, and
discuss a theoretical tool to characterize them quantitatively. This
perspective leads to insights that help to address issues debated in the
literature and also suggest pathways for future research.
