Mapping EEG Microstates Across Physiological States: A Systematic Review

Background: Electroencephalographic (EEG) microstates are transient topographic configurations that index large-scale network dynamics at the millisecond scale. Although widely studied clinically, their characterization in healthy subjects remains fragmentary, hindering the separation of normative from pathological dynamics. Methods: Following PRISMA 2020, we searched PubMed, Scopus, Springer, Web of Science and Google Scholar for studies published between June 2019 and June 2025 (PROSPERO CRD420251106374). Of 5052 records, 91 studies were included; risk of bias was assessed with ROBINS-I. Duration, frequency, coverage, topography and transition probabilities were extracted for classes A–F, and the contributing evidence was characterized by clustering solution size (K = 4 vs. K ≥ 5). Results: Microstates D and C showed the longest mean durations (78.14 and 77.04 ms), A and B intermediate values (69.24 and 66.51 ms) and E and F the shortest (59.93 and 58.75 ms); E and F were supported exclusively by solutions with K ≥ 5. The highest transition probabilities (B ↔ F, E → C) rested on only 4–5 studies, whereas the best-evidenced routes were B → A, B → C, B → D and C → D. Conclusions: These findings are a first step toward a normative reference for healthy adults, contingent on standardizing clustering, filtering and transition metrics.