Four main phenotypes represent the population of resident IBA1-IR cells in human dACC white matter. Ramified microglial cell body and highly ramified processes appear aligned to white matter tracts (a). Primed microglia display a wider cell body in the primed phenotype (b) compared to the ramified phenotype, but their processes and cell body retain a similar alignment. Reactive microglia present an amoeboid-shaped rounder cell body with a few ramified processes (c), whereas amoeboid microglia display a characteristic amoeboid-shaped cell body extending one or two unramified processes (top panel) or are completely devoid of processes (bottom panel) (d). Scale bars: 10 μm.