Monitoring neuronal activity at the local and global levels has led to the identification of several important brain areas, such as the basolateral amygdala, in emotional control; however, the underlying mechanisms remain to be fully elucidated. Here, using Arc-dVenus reporter mice, we investigated the brain-wide neuronal activation patterns following restraint stress or social defeat stress, both of which induce anxiety-related behaviors. A supervised classification of these brain-wide activation patterns showed that neuronal activation in the claustrum prominently contributes to discrimination in stressed brains. Interregional correlation analysis indicated that the Pearson correlation coefficients are prominently increased in the claustrum, infralimbic area and nucleus accumbens in both mouse models. In addition, we monitored the calcium signals from the claustrum in freely moving mice using a head-mounted miniature fluorescent microscope, and found that activity patterns of claustral neurons are different from those of previously reported amygdala neurons, during the elevated-plus maze test. Thus, monitoring neuronal activation locally and globally helps us understand the detailed mechanisms of anxiety.