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.

Neuroimaging the effects of light on non-visual brain functions

“…Data acquired in patients suffering from SAD show that a posterior area of the hypothalamus, presumably including the LH containing orexin neurons, or the PVNH, present increased activations to emotional vocal stimulation under blue light (480 nm) illumination, but decreased activation under exposure to green light (550 nm) ( Figure 21.4) [26]. These effects were not observed in healthy controls (significant difference between patients and controls).…”

MRI Techniques and New Animal Models for Imaging the Brain

“…These studies have all focused on cortical structures. The posterior hypothalamic area has been shown to play a major role in seasonal affective disorder (SAD) (Vandewalle et al 2011). The sheep has been proposed as a model for SAD as it is a photoperiodic mammal.…”

Transcranial Light Alters Melanopsin and Monoamine Production in Mouse (Mus musculus) Brain

“…Since the circadian clock is a free-running system, and produces a rhythm even when environmental cues are absent [1], it is not exactly 24 h, and thus must be entrained regularly to ensure accordingly timed physiological phenomena [2]. If the light stimulus is diminished or absent, the circadian clock is disturbed and several psychoneurological disorders, such as seasonal affective disorder (SAD) in humans, may occur [3]. Furthermore, mice have also been shown to have SAD-like behavior, when light conditions are irregular [4].…”