Table 1.

Imaging studies using a resting state paradigm to examine functional and structural abnormalities in major depressive disorder (MDD).

Study authors	Population	Paradigm	Imaging results
RESTING STATE
Hamilton et al. (2011)	MDD patients (n = 17, 10 female, 7 male). Mean age (±SD): 45 years ± 3	One fMRI scan was taken at rest (eyes closed)	↓ Activity in the right fronto-insular cortex in MDD patients in the DMN
	Healthy controls (n = 17). Mean age (±SD): 42 years ± 2	Observed default mode (DMN) and task-positive network (TPN) activations	↑ Activity in the right fronto-insular cortex in healthy controls in the TPN
Veer et al. (2010)	Recently diagnosed (< 6mo), medication-free MDD patients (n = 19, 11 female, 8 male). Mean age (±SD): 36 years ± 10	Resting-state fMRI scan (eyes closed)	↓ Functional connectivity between the left insula and the resting state network in MDD patients
	Healthy controls (n = 19, 11 females, 8 males). Mean age (±SD): 36 years ± 11
REGIONAL HOMOGENEITY (ReHo)
Yao et al. (2009)	MDD in-patients (n = 22, 12 female, 10 male). Mean age (±SD): 38 years ± 10	Resting scan (eyes closed)	↓ ReHo in right insula, ACC/PCC in MDD patients
	Healthy controls (n = 22, 12 female, 10 male). Mean age (±SD): 39 years ± 11		Anxiety severity, retardation, and hopelessness all positively correlated with ReHo in the right insula
Liu et al. (2010)	First episode un-medicated MDD patients (n = 15, 7 female, 8 male). Mean age (±SD): 29 years ± 14 First degree relatives (n = 15, 8 female, 7 male). Mean age (±SD): 38 years ± 11	Resting scan (eyes closed)	↓ ReHo in right insula in MDD patients compared to healthy controls ↓ ReHo in right insula in first degree relatives compared to healthy controls
	Healthy controls (n = 15, 7 female, 8 male). Mean age (±SD): 30 years ± 12
Guo et al. (2011)	Treatment resistant MDD patients (n = 24, 12 female, 12 male). Mean age (±SD): 38 years ± 10	Resting scan (eyes closed)	↓ ReHo in left insula in treatment resistant MDD patients compared to healthy controls
	Healthy controls (n = 19, 9 female, 10 male). Mean age (±SD): 38 years ± 10
STRUCTURAL MRI
Lee et al. (2011)	MDD patients (n = 47, 42 female, 5 male). Mean age (±SD): 46 years ± 9 Healthy controls (n = 51, 45 female, 6 male). Mean age (±SD): 46 years ± 9	Structural MRI scans were obtained to detect structural abnormalities using voxel-based morphometry (VBM)	↓ Decreased gray matter concentration was found the insular gyrus (among other limbic, cerebellar, and frontal regions) in MDD patients compared to healthy controls
			Gray matter concentration in the left insular gyrus was negatively correlated with illness duration in MDD patients compared to healthy controls

Imaging results only include those relating to insular activity.