Sparks Electrical News March 2019

LIGHTING

17

STUDY IDENTIFIES BRAIN AREA RESPONSIBLE FOR MOOD CHANGES FROM LIGHT R esearchers at the National Institute of Mental Health (NIMH) in the US have proved what has been common knowledge among lighting de- signers for years: light is important for more than just vision, and directly impacts mood and learning. when exposed to the normal light condition. However, when these mice were exposed to the abnormal light condition, the unaltered animals showed altered mood responses, whereas the genetically altered mice did not. These findings suggest that pathways from the ipRGC to areas outside of the SCN are required for driving light-based regulation of mood.

In a new study, the researchers traced the brain pathways responsible for the effects of light on learning and mood. The findings revealed that these effects are brought about by two different and distinct pathways from the retina into the brain. One of these pathways includes a previously unrecognised cluster of neurons in the thalamus, a part of the brain responsible for relaying sensory information to other brain areas. Samer Hattar, the author of the study and chief of the Section on Light and Circadian Rhythm at the NIMH, says that the research finally assigns a brain region where light can have an impact on mood, providing evidence for the positive effects of light therapy in treating depression in humans. It also challenges current thinking that changes in mood associated with alterations in day length preceded learning problems. In 2012, researchers discovered that the effects of light on learning and mood begin in the retina with a group of cells called intrinsically photosensitive retinal ganglion cells (ipRGCs). These are naturally sensitive to light, and use neural connections to provide information used in non-image-forming visual functions such as those involved in circadian photoentrainment, which is the training of an internal body clock and biological processes to correspond with light and dark periods, as well as sleep regulation. However, nothing was known about the brain pathways through which these effects occur – until now. The researchers used mice to examine the effects of ipRGCs on a part of the brain called the suprachiasmatic nucleus (SCN), which houses a central pacemaker that co-ordinates circadian- related functions across the body. The mice were genetically altered so that the ipRGCs that stimulated the SCN survived, but those that projected to places outside the SCN did not. The mice were exposed to normal light and dark cycles or to abnormal light and dark cycles. The mice and an unaltered control group, were then tested on several tasks that model learning and cognitive functions and mood. When the researchers looked at learning and cognition in the mice, they found that both the unaltered mice and the genetically altered mice showed normal behaviours in the normal light condition and abnormal behaviours in the abnormal light condition. These findings suggest that the pathways that lead from ipRGCs to the SCN are sufficient for light to impact learning and cognition. When the mood responses in the mice were examined, they found that both unaltered mice and the genetically altered mice showed no differences BRICK OR LIGHT? W ith the SIMES ‘Brick Light’, light becomes architecture itself. The product brings a new materiality to the shape of a brick, one that literally lights up a project. With five exposed faces with ice-etched finishes, SIMES ‘Brick Light’ aims to be decorative as well as structural. It is capable of bear- ing almost double the load capacity as a normal brick (100N), whilst the light quality LED light inside trans- mits for an average duration between 30 000 and 100 000 hours.

The researchers also found that the SCN connects to parts of the prefrontal cortex involved in mood regulation, and to other brain areas involved in affective-emotional processing. Remarkably, chronically activating the SCN in animals living under normal light conditions induced mood alterations, while inhibiting this region in animals living under abnormal light conditions blunted the mood changes.

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SPARKS ELECTRICAL NEWS

MARCH 2019