April 7, 2015 - In an article published in the journal eNeuro, Lawrence Morin, PhD argued that tracking the neural pathways through which light elicits sleep in nocturnal rodents can lead researchers to a better understanding of the biological mechanisms that regulate sleep. In the process Dr. Morin reviewed what is known — and not yet known — about the neural circuitry governing sleep and arousal in small nocturnal mammals.
When mice or hamsters are exposed to bursts of light during their active (night-time) phase, they stop moving about and fall asleep. At the same time, their core body temperature drops. It is known that these effects are mediated by classic photoreceptors (rods and cones) as well as intrinsically photoreceptive retinal ganglion cells which are connected either directly or indirectly to regions in the brain known to be implicated in sleep.
Teasing out the various pathways and mechanisms of transmission is not a simple task. Dr. Morin has proposed a complex model that is useful for generating hypotheses about how photic information travels to relevant regions of the brain. He anticipates that “in the future, a mixture of anatomical and functional investigations will likely provide a clear description of the photic input pathways to the sleep system” and that this task will be facilitated by studies of the effects of light on sleep. “Simple studies of light-induced sleep offer a unique opportunity to study the mechanisms underlying sleep,” Dr. Morin wrote in the article. “Nocturnal light exposure creates a convenient avenue through which entry into and emergence from the sleep state can be stimulated, explored and understood.”
eNeuro is a new open-access, peer-reviewed journal published on line by the Society for Neuroscience. Dr. Morin’s article, titled “A Path to Sleep Is through the Eye” was published on March 5, 2015.