Figure 4.

Schematic representation of the brain mechanisms involved in the non-image-forming impact of light on cognitive brain responses. (1) Responses at light onset are found within the hypothalamus (blue) and pulvinar (green) (and amygdala and hippocampus, not shown); (2) within the first seconds of the exposure, responses are found mainly in subcortical and cortical structures involved in alertness regulation (hypothalamus, brainstem (yellow), pulvinar); (3) late responses are detected at the cortical level in areas involved in the ongoing cognitive process and can subsequently affect performance. For attention/working memory/executive task (red) a network of areas around the pulvinar and including prefrontal and parietal areas appear to mediate the impact of light on alertness and cognition. For emotional responses to vocal stimuli (light blue), the network involves the hypothalamus, amygdala, and voice-sensitive area of the temporal cortex. Light seems to have a swifter impact on emotional cortical responses than attentional/working memory/executive responses. The impact of light is stronger with higher intensity, longer duration, and shorter wavelength (blue) light exposures. Time of day and the associated changes in the interaction between circadian and sleep homeostasis signals and PERIOD3 genotype modulate the impact of light. [Adapted with permission from Vandewalle et al. (2009b)].