Reward effects of light

To elucidate the reward effects of light, two experimental approaches have been adopted. An experiment for the study of the effects of exposure to a winter-like photoperiod on the diurnal rodent Arvicanthis ansorgei indicated that shortened day length with reduced light intensity induces a phase change in locomotor activity, alterations in the dopamine content in reward system structures, and alterations in clock gene expression in the suprachiasmatic nucleus. These measures were improved by daily exposure to a one-hour pulse of intense light given late in the day. In a human model, subjective affect (liking and wanting measures) determined by experience sampling was correlated with ambient luminosity measurements in participants with insomnia (a pathology with motivational deficits) and healthy controls. Two experiments were conducted in total, both outside of a laboratory setting to ensure a blind study. The findings indicated that subjective affect increases with increasing light intensity in healthy young volunteers, in contrast to an overall deficit in reward evaluation in insomniacs that is sensitive to light. Light exposure should be taken into account as a factor in determining the quality of life of insomniacs and in depression even outside of a sleep hygiene regimen. Further studies should be conducted to elucidate the effect of ambient light signals on reward circuits and how these effects change dynamically with age.