title: Abnormal hypothalamic response to light in seasonal affective disorder.
abstract: BACKGROUND
  Vulnerability to the reduction in natural light associated with fall/winter is generally accepted as the main trigger of seasonal affective disorder (SAD), whereas light therapy is a treatment of choice of the disorder. However, the relationship between exposure to light and mood regulation remains unclear. As compared with green light, blue light was shown to acutely modulate emotion brain processing in healthy individuals. Here, we investigated the impact of light on emotion brain processing in patients with SAD and healthy control subjects and its relationship with retinal light sensitivity.
  
  
  METHODS
  Fourteen symptomatic untreated patients with SAD (34.5 ± 8.2 years; 9 women) and 16 healthy control subjects (32.3 ± 7.7 years; 11 women) performed an auditory emotional task in functional magnetic resonance imaging during the fall/winter season, while being exposed to alternating blue and green monochromatic light. Scotopic and photopic retinal light sensitivities were then evaluated with electroretinography.
  
  
  RESULTS
  Blue light enhanced responses to auditory emotional stimuli in the posterior hypothalamus in patients with SAD, whereas green light decreased these responses. These effects of blue and green light were not observed in healthy control subjects, despite similar retinal sensitivity in SAD and control subjects.
  
  
  CONCLUSIONS
  These results point to the posterior hypothalamus as the neurobiological substrate involved in specific aspects of SAD, including a distinctive response to light and altered emotional responses.
authors.affiliation: Functional Neuroimaging Unit, University of Montréal Geriatric Institute, Québec, Canada. gilles.vandewalle@umontreal.ca
authors.forename: Gilles
authors.initials: G
authors.lastname: Vandewalle
authors.forename: Marc
authors.initials: M
authors.lastname: Hébert
authors.forename: Catherine
authors.initials: C
authors.lastname: Beaulieu
authors.forename: Laurence
authors.initials: L
authors.lastname: Richard
authors.forename: Véronique
authors.initials: V
authors.lastname: Daneault
authors.forename: Marie-Lou
authors.initials: ML
authors.lastname: Garon
authors.forename: Jean
authors.initials: J
authors.lastname: Leblanc
authors.forename: Didier
authors.initials: D
authors.lastname: Grandjean
authors.forename: Pierre
authors.initials: P
authors.lastname: Maquet
authors.forename: Sophie
authors.initials: S
authors.lastname: Schwartz
authors.forename: Marie
authors.initials: M
authors.lastname: Dumont
authors.forename: Julien
authors.initials: J
authors.lastname: Doyon
authors.forename: Julie
authors.initials: J
authors.lastname: Carrier
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D003116:Color; D004596:Electroretinography; D004644:Emotions / Q000502:physiology; D005260:Female; D006801:Humans; D007031:Hypothalamus / Q000098:blood supply / Q000503:physiopathology*; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D011930:Reaction Time; D016574:Seasonal Affective Disorder / Q000473:pathology*; D055815:Young Adult
chemical_list: D010100:Oxygen