Scientists Find a Brain Circuit That Could Explain Seasonal Depression (npr.org) 43
An anonymous reader quotes a report from NPR: Just in time for the winter solstice, scientists may have figured out how short days can lead to dark moods. Two recent studies suggest the culprit is a brain circuit that connects special light-sensing cells in the retina with brain areas that affect whether you are happy or sad. When these cells detect shorter days, they appear to use this pathway to send signals to the brain that can make a person feel glum or even depressed. The research effort began in the early 2000s, when [Samer Hattar, an author of the mouse study and chief of the section on light and circadian rhythms at the National Institute of Mental Health] and David Berson, a professor of neuroscience at Brown University, were studying cells in the retina. At the time, most scientists thought that when light struck the retina, only two kinds of cells responded: rods and cones. But Hattar and Berson thought there were other light-sensitive cells that hadn't been identified. The skeptics stopped laughing when the team discovered a third kind of photoreceptor that contained a light-sensitive substance called melanopsin not found in rods and cones. These receptors responded to light but weren't part of the visual system.
[Jerome Sanes, a professor at neuroscience at Brown University, and his team] team put young adults in an MRI machine and measured their brain activity as they were exposed to different levels of light. This allowed the team to identify brain areas that seemed to be receiving signals from the photoreceptors Hattar and Berson had discovered. Two of these areas were in the front of the brain. "It's interesting because these areas seem to be the areas that have been shown in many studies to be involved in depression and other affective disorders," Sanes says. The areas also appeared to be part of the same circuit found in mice. The finding needs to be confirmed. But Hattar is pretty confident that this circuit explains the link between light exposure and mood.
[Jerome Sanes, a professor at neuroscience at Brown University, and his team] team put young adults in an MRI machine and measured their brain activity as they were exposed to different levels of light. This allowed the team to identify brain areas that seemed to be receiving signals from the photoreceptors Hattar and Berson had discovered. Two of these areas were in the front of the brain. "It's interesting because these areas seem to be the areas that have been shown in many studies to be involved in depression and other affective disorders," Sanes says. The areas also appeared to be part of the same circuit found in mice. The finding needs to be confirmed. But Hattar is pretty confident that this circuit explains the link between light exposure and mood.
I'm not a bearologist but (Score:2, Interesting)
maybe a holdover from mammalian hibernation instincts?
Melanopsin (Score:5, Interesting)
The emerging roles of melanopsin in behavioral adaptation to light:
https://www.ncbi.nlm.nih.gov/p... [nih.gov]
https://en.wikipedia.org/wiki/... [wikipedia.org]
Because it's that simple (Score:3, Funny)
Re: (Score:2)
I got it, he jumped from the building roof and the ground floor is wider than the top floor, you know the skylight entrance. Suicide can be called murdering yourself.
Maybe it's just natural (Score:5, Insightful)
As an animal you're not going to do yourself much good if you burn up a ton of energy or procreate while going into the winter. So it would make evolutionary sense to have a mild seasonal depression: you should just want to hole up somewhere and not do much until conditions improve.
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Makes a lot of sense to me. Running around in the cold when there is not much to gather or hunt is probably a really bad idea.
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That was before the invention of razor blades, gelatin capsules, and handguns.
Turns out humans don't have an incredible fear of heights merely because it's dangerous to fall. Our fear of heights was multiplied by having to offset this sluggish, seasonal brick, gratuitously loaded on top of other oppressive psychological burdens by a corner-cutting mother
Re: (Score:2)
logic is a whore, I read somewhere. You can always explain why it is xyz and also why is not xyz.
That's why (Score:4, Informative)
That's why we have traditions of bringing a tree inside and lighting it brightly.
Re: (Score:1)
Because we decorate and display the fallen corpses of our mortal enemies, the trees! NEVER FORGET!
question from left field . (Score:2)
I can post this question because my teacher told me "There are no dumb questions."
So, uh, how does depression enhance our survival probability?
Sometimes it's difficult to know how inherited traits were selected for over the millennia of human development. Generally, a persistent trait can be shown to benefit those who exhibit it. I have to question the conjecture that we have evolved sensors that serve only to make us depressed.
So, while these scientists are looking through their microscopes for answers, th
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So, uh, how does depression enhance our survival probability?
Consider that sleep evolved. How does sleeping for a third of a day, in an entirely defensely state, enhance our survival probability, or increase our chances of successful procreation? I suggest depression could have evolved the same way. Sometimes, doing nothing increases survival ability. The depressed are anything but industrious.
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Generally, a persistent trait can be shown to benefit those who exhibit it.
No, that's a misunderstanding. Neutral traits can become dominant in a population, see genetic drift.
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Sometimes it's difficult to know how inherited traits were selected for over the millennia of human development. Generally, a persistent trait can be shown to benefit those who exhibit it. I have to question the conjecture that we have evolved sensors that serve only to make us depressed.
Pretty sure it's the other way around.
The sensors are for light and likely trigger pleasure sensations to encourage you to get out and be active and productive while there is more daylight to do it in.
Survival wise it used to be best to be active outdoors when it was light out, since in the dark you have a higher chance of getting eaten or seriously hurt.
Once those pleasure sensations stop, the lack of them feels like a greater difference than from a neutral level.
Probably similar in a general sense to how
Re: (Score:1)
I don't know the answer to this because every evolutionary theory is some degree of speculation. Sleep is probably the biggest one, but here are two ideas: (great book is "Why We Sleep", by Walker)
1. REM and NREM sleep have brain adaptive purposes that could not have been fulfilled any other way. Terrestrial mammals all show REM sleep (almost all, at least), whereas some aquatic mammals don't have REM sleep. We don't know what REM sleep is for but we know we need it, and being deprived of REM sleep causes o
Screen time (Score:3)
So maybe all our excessive screen time isn't so bad after all? As long as we're not showing social media on them...
Re: (Score:3)
Your screen is spectrally deficient.
This effect is not new nor a new discovery, it is very well-known and the cure is regular exposure to full-spectrum light. This is very deeply rooted in the limbic system and evolutionary history, essentially, since there were parietal eyes.
Circuit? (Score:1)
Why do they keep calling neural pathways circuits? Where's the backchannel? It seems to be one way.
didnt scientist say SAD didnt exist? (Score:1)
Re: (Score:2)
According to your link, a phone survey found that winter depression doesn't seem to be a thing, although it's possible that SAD is some other type of mood disorder; or it's just very rare.
Even if the study results matched the headline ... (Score:3)
With headline: "Study Finds "Seasonal Affective Disorder" Doesn't Exist"
Science is about getting closer to the truth by replacing less-accurate, inaccurate, and just plain wrong ideas with ones that are more accurate.
ANY study is subject to being found to be wrong or not-so-hot and its conclusions replaced by better ones.
Even if all the studies were perfo
There's ways... (Score:2)
Re: There's ways... (Score:1)