Bright-light intervention induces a dose-dependent increase in striatal response to risk in healthy volunteers

Neuroimage. 2016 Oct 1:139:37-43. doi: 10.1016/j.neuroimage.2016.06.024. Epub 2016 Jun 16.

Abstract

Bright-light interventions have successfully been used to reduce depression symptoms in patients with seasonal affective disorder, a depressive disorder most frequently occurring during seasons with reduced daylight availability. Yet, little is known about how light exposure impacts human brain function, for instance on risk taking, a process affected in depressive disorders. Here we examined the modulatory effects of bright-light exposure on brain activity during a risk-taking task. Thirty-two healthy male volunteers living in the greater Copenhagen area received 3weeks of bright-light intervention during the winter season. Adopting a double-blinded dose-response design, bright-light was applied for 30minutes continuously every morning. The individual dose varied between 100 and 11.000lx. Whole-brain functional MRI was performed before and after bright-light intervention to probe how the intervention modifies risk-taking related neural activity during a two-choice gambling task. We also assessed whether inter-individual differences in the serotonin transporter-linked polymorphic region (5-HTTLPR) genotype influenced the effects of bright-light intervention on risk processing. Bright-light intervention led to a dose-dependent increase in risk-taking in the LA/LA group relative to the non-LA/LA group. Further, bright-light intervention enhanced risk-related activity in ventral striatum and head of caudate nucleus in proportion with the individual bright-light dose. The augmentation effect of light exposure on striatal risk processing was not influenced by the 5-HTTLPR-genotype. This study provides novel evidence that in healthy non-depressive individuals bright-light intervention increases striatal processing to risk in a dose-dependent fashion. The findings provide converging evidence that risk processing is sensitive to bright-light exposure during winter.

Keywords: Bright-light intervention; Seasonal affective disorder; Ventral striatum.

MeSH terms

  • Adaptation, Physiological / physiology
  • Adaptation, Physiological / radiation effects
  • Adolescent
  • Adult
  • Brain Mapping
  • Choice Behavior / physiology*
  • Choice Behavior / radiation effects*
  • Corpus Striatum / physiology*
  • Corpus Striatum / radiation effects*
  • Dose-Response Relationship, Radiation
  • Humans
  • Light*
  • Lighting / methods*
  • Male
  • Middle Aged
  • Photic Stimulation / methods
  • Radiation Dosage
  • Risk-Taking*
  • Young Adult