Figure 2.

Significant brain regions showing negative correlation with characteristics of patients with chronic primary insomnia. With the controlled confounders of age, sex, and intracranial volume, a negative correlation was observed between gray matter concentrations (GMCs) in the left middle frontal gyrus and the Insomnia Severity Index (r = -0.613, P = 0.014) (A), between GMCs in the right postcentral gyrus and the sleep latency (r = -0.411, P = 0.019) (B), and between GMCs in the right precentral gyrus and the wakefulness after sleep onset (r = -0.443, P = 0.018) (C).