Summary: Passing too much time in rooms and offices with dim light, may as a matter of fact, change the brain's structure and harm a person's ability to recall and understand.
The brains of Nile grass rats(which, like humans, are diurnal and sleep at night) was studied after exposing them to dim and bright light for four weeks.The rats exposed in dim light lost about 30 percent of capacity in the hippocampus, a critical brain region for learning and memory, and performed poorly on a spatial task they had trained on previously.
The rodents exposed to bright light, on the other hand, showed significant improvement on the spatial task. Furthermore, when the rats that had been exposed to dim light were then exposed to bright light for four weeks( after a month-long break), their brain capacity and performance on that task, recovered fully.
The research is the first to show that changes in environmental light, in a range normally experienced by humans, leads to structural changes in the brain.
As soon as the rats where exposed to dim light, mimicking the cloudy days of Midwestern winters or typical indoor lighting, the animals showed impairments in spacial learning. This is comparable to when people can't find their cars in a busy packing lot after a few hours in a shopping mall or movie theater.
Prolonged exposure to dim light led to significant reductions in a substance called brain derived neurotrophic factors- a peptide that helps maintain healthy connections and neurons in the hippocampus and in dendritic spines, or the connections that allow neurons to communicate with one another.
Following the fact that there are fewer connections being made, this results in diminished learning and memory performance that is dependent upon the hippocampus.
Amusingly, light does not directly affect the hippocampus, meaning it acts first on the sites within the brain after passing through the eyes. The research group is investigating one potential site in the rodent's brain- a group of neurons in the hypothalamus that produce a peptide called orexin, that's known to influence a variety of brain functions. One of the main research questions-If orexin is given to the rats that are exposed to dim light, will their brains recover without being re-exposed to bright light?
The project could have implications for the elderly and people with glaucoma, retinal degeneration or cognitive impairments.
Considering people with eye disease who don't receive much light, can we directly manipulate this group of neurons in the brain, bypassing the eye, and providing them with the same benefits of bright light exposure?
Further possibility is improving the cognitive function in the aging population and those with neurological disorder. Is it feasible that we can help them recover from the impairment or prevent further decline?
Story source:
Material given by Michigan State University. Note: Text may be improved for style and length
Journal Reference:
- Joel E. Soler, Alfred J. Robison, Antonio A. Nunez, Lily Yan." Light modulates hippocampal function and spatial learning in a diurnal rodent species: A study using male nile grass rat ( Arvicanthis niloticus)".
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