Introduction: Seasonal affective disorder (SAD) is considered as a sub-type of recurrent major depressive disorder (MDD) in which depressive episodes regularly begin in one season and remit in another season [2]. Light has been shown to be an effective treatment for the disease [6,8]. A new therapy for SAD has been proposed a extra-visual light (EVL) therapy via ear-canals. We have studied whether the effect of SAD and EVL on functional connectivity of resting-state brain networks overlap spatially.

Methods: 

45 (39.78 ± 10.64 years) antidepressant-free SAD patients (HAMD-17 and SIGH-SAD [9]) and 45 matched controls were imaged at same winter-period. Another 50 subjects (29±6 years) were divided into two blinded groups (24 vs. 26 subjects) in which the other received EVL at the 2nd fMRI scan. Resting-state BOLD data on GE 1.5 THdxt: TR 1800 ms, 280 whole brain volumes. MELODIC ICA data was dual regressed for analyzing RSN effects of both SAD and EVL between groups [1,3,4]. Voxel level p < 0.05 corrected for multiple comparisons with TFCE in FSL randomize were overlaid on MNI 152 brain coordinates.

Results: 

SAD increased functional connectivity in RSN mostly in visual and sensorimotor (SM) networks and thalamus. EVL affected the same SM and visual networks with partially overlapping effects. These areas are know to be light responsive.

References: 

1.Abou Elseoud et al.,2010,HBM: 1207–1216. 2. American Psychiatric Association (2000) 3. Beckmann CF et al., 2004 IEEE Trans Med Imaging 137–152. 4. Filippini et al.,2009 Proc Natl Acad Sci USA, pp. 7209–7214. 5. Perrin et al.2004 Current Biology, pp. 1842–1846. 6. Rosenthal et al.,1984, Arch Gen Psychiatry, pp. 72–80. 7. Vandewalle et al., 2007 Cerebral Cortex, 2788–2795. 8. Virk et al., 2009 Int J Disabil Hum Dev, 283–286. 9. Williams et al., (1994) SIGH-SAD